JBED
Journal of Building Enclosure Design
An official publication of the Building Enclosure Technology and Environment
Council (BETEC) of the National Institute of Building Sciences (NIBS)
Summer/Fall 2008
The Best of the BEST 1 Conference:
Experts Meet in Minneapolis
to Discuss Building for
Energy Efficiency and
Durability at the Crossroads
Summer/Fall 2008 1
2 Journal of Building Enclosure Design
JBED
Published For:
NIBS / BETEC
1090 Vermont Avenue, NW, Suite 700
Washington, DC 20005-4905
Phone: (202) 289-7800
Fax: (202) 289-1092
nibs@nibs.org
www.nibs.org
Published by:
Matrix Group Publishing
Please return all undeliverable addresses to:
16516 El Camino Real
Suite 413, Houston, TX 77062
Phone: (866) 999-1299
Fax: (866) 244-2544
Contents
Features:
11
27
Energy Efficiency and
Durability of Buildings at
the Crossroads
39
Field Monitoring of
the Hygrothermal
Performance of a New
Class of EIFS Walls
47
Detection of Moisture
and Water Intrusion
Within Building
Envelopes By Means of
Infrared Thermographic
Inspections
President & CEO
Jack Andress
Senior Publisher
Maurice P. LaBorde
publisher & director of sales
Joe Strazzullo
jstrazzullo@matrixgroupinc.net
Editor-in-Chief
Shannon Lutter
shannonl@matrixgroupinc.net
Finance/Accounting &
Administration
Shoshana Weinberg, Pat Andress,
Nathan Redekop
accounting@matrixgroupinc.net
Director of Marketing &
Circulation
Shoshana Weinberg
Sales Manager
Neil Gottfred
Matrix Group Publishing
Account Executives
Albert Brydges, Davin Commandeur, Rick Kuzie,
Miles Meagher, Ken Percival, Peter Schulz, Vicki
Sutton, Declan O’Donovan, Jessica Potter, Bruce
Lea, Kevin Harris, Brian Davey, Jim Hamilton
Advertising Design
James Robinson
Layout & Design
Travis Bevan
©2008 Matrix Group Publishing. All rights reserved.
Contents may not be reproduced by any means, in
whole or in part, without the prior written permission of the publisher. The opinions expressed in
JBED are not necessarily those of Matrix Group
Publishing.
Water
Intrusion
Field Measurements
of Moisture in Building
Materials and Assemblies:
Pitfalls and Error
Assessment
60
47
of PCM-Enhanced
55Use
Insulations in the Building
Envelope
R-Value of
60Real
Exterior Insulated Wall
Assemblies
Real-R PCM-Enhanced
Values
Insulations
55
Messages:
7
9
Message from NIBS President,
David A. Harris
Message from BETEC Chairman,
Wagdy Anis
Industry Updates:
67
72
BEC Corner
70
Buyer’s Guide
BETEC/NIBS Membership On the cover: Minneapolis,
MN was host to the BEST 1
Conference in 2008.
Photo courtesy of Josh Norton.
Summer/Fall 2008 5
Message from NIBS
in the awards presented to those mentioned
above at the opening ceremony, Jacqueline
Hardman accepted a posthumous award for
BETEC’s Vice Chair, Barry Hardman, for his
many years of dedicated service to BETEC
and the building community.
David A. Harris, FAIA
Over the past few years I have watched
with pride as BETEC and the Building Enclosure Council have grown under the extraordinary and tireless leadership of Wagdy Anis.
Contributions by BETEC and BEC to the
positive improvements in building enclosure
design and delivery are unsung, but non-theless appreciated, albeit anonymously, by all
who benefit from the professional knowledge and dedication of these councils. It is
most gratifying to see our industry’s talented
professionals work together cooperatively to
achieve technical advances none could have
achieved individually.
The BEST1 Conference held in Minneapolis in June, and featured in this issue,
was a collaborative effort of the Building
Enclosure Council, BETEC and its supporting sponsors. The success of BEST1 was
due to the team work and contributions of
the conference committee who planned and
organized the event. Rob Kistler, AIA, of
The Facade Group, Inc. and Judd Peterson,
AIA, of the Judd Allen Group, served ably
as co-chairs of the Conference. As leaders
of the technical committee, Dr. Donald
Onysko and Dr. Mark Bomberg did an
exceptional job in reviewing and organizing the many excellent technical papers
presented at the conference. Appreciation
is due for AIA National, AIA Minnesota,
BETEC, BEC Minnesota and BEC-National
for their support and contributions. Be sure
to pencil in the BEST2 Conference to be
held in Portland, Oregon in 2010. Included
In this critical time for
the facilities industry I
urge each of you to join in
the many facets of NIBS’
many initiatives to transform our 100 year-old linear and repetitive paperbased building process
into one that wisely and
efficiently utilizes information and data to virtually
design, construct, operate and maintain new and
existing buildings with less
waste and more efficient
use of human and other
resources.
This will be my last opportunity to address
you, the readers of JBED, as NIBS president
as I am retiring this year. I am delighted to
turn the reins over to my good friend and
colleague Henry L. Green, Hon. AIA, who
has been selected by the Institute’s Board of
Directors as the next President and CEO of
the National Institute of Building Sciences. I
could not be more pleased with his selection and am confident that Henry will lead
NIBS to the next level where it will help
to achieve a new array of improvements to
the building process and dramatic improvements in the performance of tomorrow’s
buildings. I have known and worked with
Henry for many years on NIBS’ programs
and initiatives of BOCA, International and
the International Code Council. He is well
known to and highly respected by leaders
of the building community and by the NIBS
staff. He is an innovative and thoughtful
leader with the background, talent and
knowledge to reach out to and work with
all sectors to help improve our vast industry. As a past NIBS Board chairman and the
immediate past chairman of NIBS’ Building
Seismic Safety Council he well understands
NIBS’ and its programs.
Since 1989, Green has been the executive director of the Michigan Bureau of
Construction Codes. In that position, he has
provided executive management and oversight for construction codes programs in the
State of Michigan including the development
and implementation of construction codes
and standards, building inspection programs,
and public education programs. As a volunteer, Green has served as the president
of the International Code Council (ICC)
and president of one of ICC’s legacy organizations, the Building Officials and Code
Administrators, International. His contributions and accomplishments have been
widely recognized by numerous awards
and honors from a host of building industry
organizations.
In this critical time for the facilities industry I urge each of you to join in the many
facets of NIBS’ many initiatives to transform
our 100 year-old linear and repetitive paperbased building process into one that wisely
and efficiently utilizes information and data
to virtually design, construct, operate and
maintain new and existing buildings with less
waste and more efficient use of human and
other resources. You can help to achieve
this transformation by getting involved. You
are critical to the success of these essential
advances for the future of our industry. So
join with your U.S. and international colleagues today by becoming a member of the
BETEC, BEC, the buildingSMART Alliance,
the High Performance Buildings Council or
one of NIBS’ other councils and programs.
You will be in very good company!
David A. Harris, FAIA
President
National Institute of Building Sciences
Summer/Fall 2008 7
Message from BETEC
While I wish we could feature all of the excellent
presentations, the essence and spirit of BEST 1 has
been captured and is summarized in BETEC’s white
paper, Energy Efficiency and Durability of Buildings
at the Crossroads (page 27). Its imperative message,
that we can no longer conduct “business as usual” in
the design of buildings, is a call to action to reduce
energy/resource demands by improving the energy
efficiency and durability of buildings, due to dwindling
global energy supplies and climate change.
Wagdy Anis, FAIA, LEED AP
Welcome and congratulations
to three new BEC Chapters that joined
us this year—BEC San Francisco, BEC Wisconsin and BEC South Eastern Michigan
(Detroit). We now have 22 BEC Chapters. Information on the Building Enclosure
Council and its chapters can be found at
www.BEC-National.org.
We hope you enjoy this edition, and as
always, we welcome your comments and
suggestions.
The first Building Enclosure Science
and Technology Conference (BEST 1),
hosted by both AIA Minnesota and BEC
Minnesota in June was attended by nearly
250 participants from North America and
Europe. I echo Dave Harris’ thanks to the
supporting sponsors, hosts, and organizers as well as staff and volunteers who
contributed to the success of the conference. As Dave mentioned, plans for
BEST2 are underway. A call for abstracts
for BEST2 is listed in this issue. Conference information will be posted at www.
thebestconference.org.
While I wish we could feature all of the
excellent presentations, the essence and
spirit of BEST 1 has been captured and
is summarized in BETEC’s white paper,
Energy Efficiency and Durability of Buildings
at the Crossroads (page 27). Its imperative
message, that we can no longer conduct
“business as usual” in the design of buildings,
is a call to action to reduce energy/resource
demands by improving the energy efficiency
and durability of buildings, due to dwindling
global energy supplies and climate change.
This issue indeed marks a transition
at NIBS with Dave Harris’ retirement as
president. Our collective good wishes are
extended to Dave to enjoy his retirement.
He leaves NIBS with a gigantic track record
of forging new ground and establishing
national initiatives in improving the building
process as president of the National Institute of Building Sciences. He has been an
avid supporter of BETEC, was instrumental
in establishing the May 2004, agreement
with the AIA to establish the Building Enclosure Councils (BECs), and in the formation
of BEC-DC. Most recently, Dave was a
key player in the tripartite memorandum
of understanding between NIBS, AIA and
the National Building Envelope Council of
Canada to collaborate on matters of building enclosure, hold conferences, advance
education and the like. Last May, during
the BEC breakfast at the AIA Convention
in Boston, David Harris, Christine McEntee,
AIA’s executive vice-president/CEO, NBEC
president Ryan Dalgleish, and I signed the
MOU.
A hearty welcome to NIBS’ new president, Henry L. Green, Hon. AIA, who brings
his stellar building community career of
knowledge and experience to the Institute.
Wagdy Anis, LEED AP, FAIA,
Principal, Wiss, Janney, Elstner
Associates, Inc.
Chairman of BETEC
Chairman of the Editorial Board of JBED
wanis@wje.com
www.wje.com
Summer/Fall 2008 9
10 Journal of Building Enclosure Design
Feature
Field Measurements of
Moisture in Building
Materials and Assemblies:
Pitfalls and Error Assessment
By Donald M Onysko, Christopher Schumacher and Peter Garrahan
ABSTRACT
Moisture meters are becoming ubiquitous in their use on building sites by building inspectors, supervisors, installers of flooring
finishes, and other building specialists in their forensic work. The
point of their use on construction sites is to enable their users to
identify and avoid excessive built-in moisture or to determine why
a moisture problem has developed. When things go badly and
building scientists are called in to investigate failures moisture meters are essential tools to assist in the early stages of an investigation. The trouble is that many users are novices in their use and in
the interpretation of readings provided by a moisture meter.
There are several families of tools available to enable practitioners to apprize themselves of the amount of water stored in
materials and to judge whether the levels measured pose a risk to
the assembly once completed. These tools include handheld resistance-based and capacitance-based moisture meters and others.
This paper will provide some of the background to the accuracy
of handheld moisture meters and some of the pitfalls in their use
and interpretation. Unless they are in the hands of a knowledgeable user, they should not be used solely as the basis for undertaking major remediation works without more detailed investigation.
BACKGROUND
Increasingly, moisture meters designed for industrial use in
the wood industry are being used for field investigation of structures by persons who do not have the experience in their use or
an understanding of their limitations. As part of the background
in their use, it is important to understand the purpose for which
they were developed and the basis for the extensive research
that underpins their use.
Measurement of the moisture content of lumber has been of
prime importance to the wood industry for many years. Lumber
producers need to know that their kiln operations achieve the target moisture content for KD lumber—more drying than necessary
is costly for the extra energy needed, reduced productivity at the
kilns, and increased levels of shrinkage and warp. Also, shipping
lumber to distant markets that contains more water than desired
(hence shipping weight) cuts into profit margins. Finally, drying
(whether by kilns or air drying) is needed to avoid sap stain of
wood having high moisture, and to arrest either incipient or new
decay from progressing while it is in storage or being shipped.
To meet these needs, particularly for wood industries that
depend on speedy delivery to markets often across long distances, moisture meters have been developed based on the relationship between the electrical resistance or dielectric properties of
wood and its moisture content. From these initial developments,
meters have also been developed for other materials and applications, based on the same principles.
Research on the factors that influence the resistance or dielectric properties of wood is extensive. Yet, there is a lack of
appreciation for the uncertainty of the measurements made. It
is one thing to accept a certain degree of variation in lumber
that is kiln dried as a shipment. It is another matter to use these
meters in the field to interpret whether there is or is likely to
be moisture damage. Particularly egregious is the case where a
code–imposed limit is required to be met by builders of wood
framed buildings and an inspector dogmatically decides that the
moisture meter readings above the limit indicate a structure is
too “wet” to proceed with. Or, that on the basis of probing a
few locations in an existing building, with a fixation on a codeimposed or unofficial understanding of the consequences of
moisture retention, a building inspector decides that the envelope is in trouble and must be remediated, often at great cost.
The purpose of this paper is to assist those not fully informed
in wood moisture measurement and to provide a summary of
the factors that influence moisture content readings. We will also
discuss how this information should influence the measurement
in the field and interpretation of the findings using these types
of meters. The paper expands upon discussion and information
provided in other guidelines [13].
WHY MEASURE MOISTURE CONTENT?
Building codes in the U.S. and Canada, and indeed in many
other countries, specify that lumber be dry at the time of installation in buildings. The definition of “dry” lumber in the North
American context (as defined by the National Lumber Grades
Authority [NLGA]) is wood having a maximum moisture of 19
percent on a dry weight basis. This is a typical moisture content that air-dried lumber can achieve in covered, outdoor
storage. This requirement is derived from a long history of scientific research and experience involving good practice by the
construction trades.
The justification for the 19 percent specification does not
seem to be recorded.
Summer/Fall 2008 11
Figure 1. DC-resistance moisture meter (on left) and dielectric moisture meter (on right).
However, it has long been recognized in the lumber industry
that once logs have been sawn into lumber, if drying conditions
are poor or the lumber is close-piled, there is opportunity for
fungal infection and staining which may degrade its appearance
and render it to be less marketable.
The following quotation was taken from an early edition of
the Wood Handbook (1940 revision) [1] in a discussion of storage of lumber at yards (p 205).
“Lumber that has a moisture content higher than 20
percent is likely to become stained or decayed when
piled solidly. On the other hand, lumber, even though
at a moisture content of less than 20 percent, when not
properly protected against the weather is apt to stain or
decay.”
This was at a time when the majority of wood was air dried and
12 Journal of Building Enclosure Design
had become exposed to spores of decay fungi during exposure
before sufficient drying. Today, we recognize that while existing
decay may continue until the wood is dried below 20 percent, reinfection of kiln dried (normally sterile) wood by decay fungi will
not occur unless the moisture content approaches the fiber saturation point (typically 28-30 percent MC) [2]. The 20 percent rule is
now considered to provide a “reasonable margin of safety against
fungal damage” [3]. In other words, there is a built in safety factor
of some unknown amount in that recommendation.
Despite those requirements, builders have not always used
dry wood. Traditionally, green wood has often been used but
construction practices made allowances for sufficient drying to
take place of the finished building assemblies.
From a forensic point of view, measurement of moisture
content of wood and other materials is incidental to the main
question having to be answered. For whatever reason questions
were raised that required an investigation, the main goal is to decide whether or not there is a potential problem, and to decide
what to do about it if there is a problem. The use of moisture
meters is an aid to develop some understanding of the condition
of a structure without further destructive investigation.
Industry drying practices
It is useful for persons investigating the health of a building assembly to know a little bit about the nature of the basic material
they are dealing with. Most commercial lumber used in construction is from softwoods, i.e., from conifers that do not loose their
foliage on a yearly basis.
North American softwood lumber producers use large, batchloaded kilns to dry lumber under controlled conditions of temperature, relative humidity, and airflow. Variables such as species, initial
moisture content, dimension, and other characteristics, affect drying times. Even after taking all of these variables into consideration,
wood remains a complex material to dry. Natural variations in grain
pattern, density, and the amount of sapwood/heartwood result in a
certain amount of variability in the final moisture content. For these
reasons, end users must expect and be prepared to accommodate
for a certain amount of variability in the final MC. In fact although
the NLGA grading rules specify 19 percent as the required upper
limit for average moisture content, there is an allowance for up
to 5 percent of the pieces in a charge to be in excess of this level.
This is to reflect the variability in the material and the difficulty in
drying all pieces to the same final MC.
Virtually all kilns in the softwood construction lumber industry
are of the heat-and-vent (or conventional) variety. Heat-and-vent
dryers used in the drying of dimension lumber are large chambers with forced air circulation systems and controlled temperature and relative humidity systems. Drying schedules may employ maximum temperatures of 180 to 190°F (82 to 88°C) in
conventional kilns and up to 240°F (115°C) in high-temperature
kilns. These temperatures are sufficient to kill all insects and any
other organisms that might be present in the wood.
Computerized controls are used in most dry kilns to monitor
and control the drying conditions and to collect some data on the
moisture content (MC) of the material in the process. There are
no practical systems available to accurately measure the moisture content of wood in a dry kiln. Kiln operators have data/tools
available to assist in determining the end point for drying, but,
for the most part, accurate measurement of MC cannot be conducted until after the wood is removed from the kiln.
Moisture content sampling at the planer mill is the point in the
process where the most accurate and greatest quantity of information can be gathered. Many of the larger softwood mills employ inline moisture meters to monitor the MC of every piece of lumber
processed. If well calibrated and maintained, such instruments can
provide average estimates of the MC to within plus or minus one
percent of the “true” mean batch MC of most species. Spot checks
with handheld moisture meters are also usually conducted at various
points in the dressing (surfacing), grading, and packaging process.
Mills rely on such information to verify conformance with
MC specifications and provide feedback to the dry kiln operator.
Summer/Fall 2008 13
Sampling of final MC by the oven-dry method may provide accurate information on an individual board basis but it is impractical for
obtaining an accurate picture of the condition of the entire load.
These practitioners know their materials, they know their
sources, and they understand the drying processes involved.
Significant variability can still be found from piece to piece within
a kiln charge depending on how the drying actually took place.
But these variations gradually reduce in protected lifts of material
as moisture gradients decline and diffusion takes place within the
stack during subsequent periods of storage and transit.
Historic versus current building practices
In the past, construction practices were forgiving to both higher
initial MC’s and wetting that occurred during the building process.
Construction scheduling was slower than today and permitted
gradual drying of the standing wood frame structure. Use of lumber
subflooring permitted drainage of moisture that impinged on the
partially completed structure and prevented ponding of water on
floors. Lumber wall sheathing was very permeable to both air and
vapor movement and resulted in rapid drying of excess moisture in
the wall cavities. Also, low levels of insulation permitted greater heat
loss that contributed to more rapid drying after construction.
With the application of lath and plaster finish for the interior,
a wet process, drying was needed before the final finish plaster
coat was applied. This was commonly done after a longer period of time when sufficient drying and building settlement had
occurred to allow any shrinkage cracks to be manifest and to
be repaired before the final finish coat and paint were applied.
These building practices are not now commonly employed in
North America.
Currently, dry rather than wet practices for interior finishes
are used; use of plywood and OSB panels for floor, wall and roof
sheathing, and the use of power tools all provide for greater flexibility, ease of assembly, and speed of construction. Faster construction times are encouraged by the costs tied up in purchasing
the land, and the labor and materials for construction.
In quite recent times, there has been concern about the degree to which construction moisture is being locked in to wood
framing at the time of construction. In 1991 CMHC published a
report of a study they had commissioned Forintek to undertake
to assess this issue across the country [4]. The moisture content
of framing in wall studs and plates of over 515 houses under construction were assessed at 10 regional centers and at 4 different
seasons of the year. In some parts of the country, S-GRN lumber
was used predominately and high moisture levels were measured. When S-DRY lumber was used, moisture contents tended
to be lower, but at some sites, even this lumber was found to
contain moisture contents above fiber saturation (fiber saturation is considered to be approximately 30 percent). Bottom wall
plates had higher moisture contents than wall studs because they
were more vulnerable to absorbing rainfall due to their position
and less surface area exposed for subsequent drying.
This discussion helps define the potential initial moisture conditions that building assemblies may have experienced by the time of
construction and from which changes will have taken place prior to
investigation by a building inspector or forensic engineer or architect.
Consequences of drying IN SITU: shrinkage
We have touched on building practices that were used in the
past to deal with shrinkage-induced effects related to drying. It
is worth pointing out that whether lumber framing conforms or
does not conform to the regulation concerning moisture content
in the building codes, shrinkage effects still have to be accounted
for in construction. The equilibrium moisture content (EMC)
finally attained by lumber in the building may be 8 percent or
lower depending on its location in the building and the climate.
The transverse shrinkage of green lumber as it dries to its end
point EMC can be as much as 4.5 percent. Dry lumber meeting
code requirements will experience significantly less shrinkage but
it still can be expected to shrink in the order of two percent. The
consequences of shrinkage are nail popping leading to loss in air
tightness (and drywall plaster popping), differential settlement
leading to drywall cracks, floor squeaks, and building height settlement leading to potential problems with vertical plumbing stacks.
These problems are normally associated with the initial drying-out
period as lumber dries to its EMC. Our current building practices
can accommodate for these effects. Probably the most important
concern is the need for more careful attention to installation of
air barriers and vapor barriers. This caution is to alert the reader
to one type of change that affects how the heat, air and moisture
performance of wood assemblies can be affected.
How to judge that excessive moisture may be the cause of or may
contribute to problems down the road? To make these judgments
it is essential that the person undertaking the investigation knows
about the likely behavior of the “system” he/she is investigating.
14 Journal of Building Enclosure Design
Generally, if the desired moisture is 19 to 20 percent dry weight
basis with no more than 5 percent of a shipment in excess of this
level, it is considered “dry” because once installed in a building and
protected, the MC will gradually decline and dry. It has been a long
established practice that this is a safe level at which wood would
not promote mold growth and encourage decay. The tolerance on
exceeding the limit is to acknowledge the presence of other permitted species in the kiln charge that dried at a different rate.
Of course once that lumber is installed in a structure, the rate
of drying becomes dependent on the assembly that is quite different from that in a protected close piled lift. How that drying
proceeds depends on the environment surrounding the individual pieces which is a function of the building practices during
construction and the makeup of the building assembly.
With the above sections as introduction, we will now summarize some of the factors that influence the accuracy of the
estimate of moisture content that will be obtained using commercial moisture meters in a field inspection setting. Our primary
emphasis will be on resistance based meters, but both they and
dielectric based meters are tools that serious investigators will
need to use, often at the same location.
DC-RESISTANCE BASED METERS
Essentially, DC-resistance based meters are ohm meters
that have a scale or output calibrated for some reference species of wood. The reference species used by many manufacturers in North America is Douglas-fir, using a relationship that
was obtained by the USDA Forest Products Laboratory (James
1963). This was most likely old growth Douglas-fir and the relationships developed would be specific to that material. Initially,
moisture meters produced were calibrated for that species only.
When used to measure the moisture content of other species,
a correction was required. Extensive calibration studies were
undertaken for numerous species to enable an industry standard resistance based moisture meter to be used throughout
the industry and tables were published to allow these Douglasfir calibrated, DC-resistance meters to be used by lumber producers [5, 6]. Since then extensive research has been done to
allow the use of these meters down to a wood temperature
of -4°F (-20°C) and lower. This was necessary since significant
errors were found for frozen wood [7]. Data from many studies have been recast into one correction equation for various
species and wood temperatures from -20 to 120 °F (-29°C to
48.8°C) [8].
Meters are now available that allow individual species and wood
temperatures to be selected. These meters have been programmed
to automatically compensate for species and temperature effect. The
relationships programmed into the meters are, in most cases, based
on the various research papers listed in the bibliography. Those having the capability of selecting for specific species and temperature,
and that have been properly calibrated using appropriate sampling
techniques, are more likely to give readings that are closer to the
mean moisture content of the wood than others.
Electrical circuits in wood
When good contact is made between the pins of a DCresistance meter and a piece of wood, a path is provided for
current to flow between the two pins. In the equivalent electronic circuit of Figure 2, wood, as a dielectric, can be represented
as a simple parallel circuit including a resistance and a capacitor.
In this idealized circuit, when current is first turned on, electrons
flow through the wood as idealized as a resistor and charge begins to accumulate in the capacitor. As charge continues to build
the apparent resistivity drifts. This analogy hides the complexity
of actual current and ionic flow in this natural dielectric material
[15]. The movement of free ions is slower than that of electrons
and they move toward one or other of the pins and the current
flow diminishes with time as they accumulate at the interface between the pin surface and the wood. This mechanism explains
the low conductivity (e.g. high apparent resistance) of wood and
the fact that the resistance increases with temperature [9].
When no charge is present the ions tend to diffuse randomly,
however in the presence of an electric field ions move towards
and accumulate around the electrodes, causing the material to
become polarized. While this phenomenon has little effect on
short, one-time measurements made with hand-held analog
MC meters, it can have significant effect on longer, continuous
measurements or periodic in-situ measurements using such instruments. Digital commercial MC meters are designed to take
the measurements over a very short fixed period of time and at
a low applied voltage to minimize polarization. Periodic in-situ
measurements will be discussed later in this paper.
Use of handheld meters—4 or 2 pins and orientation
The pins should be inserted parallel to the grain and in a region
away from defects such as knots, pitch pockets, or decay. When
interpreting measurements in material containing a moisture gradient, insulated pins should be used. These are specially coated
with a non-conducting material and shaped to resist abrasion when
being driven in. The tips are not insulated and the MC reading taken is relevant to the wood in the region and depth to which the
pins have been driven. For thinner materials, and where moisture
gradients are not likely, non-insulated pins are typically used. Use
of non-insulated pins provides one an idea of the upper level of
moisture present, not the average if that is of interest, or of the
moisture content in a particular veneer in plywood. For measuring
moisture content of product having veneers, 4 pin tools are useful
because one does not need to be concerned about the grain direction of the particular veneer being probed.
Figure 2. The equivalent circuit.
Summer/Fall 2008 15
In-situ measurements
In-situ measurements can be made by driving pairs of pins
with lead wires into select locations. The moisture content at
these locations can be measured by connecting the leads to the
pins of a handheld meter as illustrated in Figure 3. In this case a
pair of 3/4 inch (19 mm) stainless steel pins has been used as the
in-situ electrodes. All but the tip and a band under the head have
been coated with ceramic engine paint and cured in an industrial
oven to provide an abrasion resistant, non-conductive (i.e. insulating) finish. Once the pins are installed the exposed solder joints
are coated with insulating electrical tape to prevent the possibility of current flow through wet adjacent materials such as insulation. A thermistor can be installed in parallel to the moisture pins
to allow for temperature calibration where necessary.
In-situ measurements can be useful whenever periodic measurements must be made at the same location or wherever it will be
difficult, too costly or too destructive to get to the measurement
location at the time that the measurements are to be made. Using
this approach, one can monitor the drying of construction moisture
or moisture introduced by a wetting event. It can be used to permit
periodic moisture content checks in problem areas after repairs.
Issues that influence DC-resistance based measurements
Species effects and temperature effects
An extensive series of studies at the Eastern and Western
Forest Products labs in Canada (now FPInnovations) and the
USDA Forest Products Laboratory over many decades have
led to a fairly reliable formulation to make corrections for meters that are calibrated or designed for Douglas-fir and used at
a setting appropriate for that species. This has been based on
very extensive research over many decades in both the U.S. and
Canada.
Species is one factor that is known to have an impact on
DC-resistance meter readings. Although specific gravity varies
between species, the species effect on DC-resistance is also related to differences in the chemical (extractive) composition of
the wood. In order to apply a species correction requires some
knowledge of the species being tested. People in the wood industry know the trees they are machining and can even differentiate between individual species within a family of conifers. For
example, some spruces can only be identified by examining both
the wood and the bark of the tree.
This has a direct bearing on the accuracy of estimating the
moisture of lumber. At a sawmill site it is relatively easy to identify which species is being tested. In other circumstances there
is much less certainty by persons outside of the wood producing
industry. If species cannot be determined with certainty, the user
must bear this in mind when considering the potential accuracy
of readings that are obtained.
For any given moisture content, the apparent resistance of
wood is dependent on the temperature of the wood - the higher
the temperature the lower the resistance. Temperature corrections were first developed at the USDA by James [9] using 73°F
(23.8°C) as the reference temperature. However several research
studies have shown that this relationship makes corrections that
severely over estimates the moisture content for wood at low
temperatures, particularly for frozen wood. On the basis of extensive studies a relationship was provided that enabled DC-resistance
meters to be used more reliably over a wide wood temperature
range. The single formula accounting for the effect of both species
and wood temperature developed was [8]:
[
MC =
R + 0.567 - 0.0260T + 0.000051T2
0.881(1.0056)T
MC = corrected meter reading
R = meter reading
T = wood temperature ºC
a and b = species correction coefficients (calibration at 22.8ºC)
While this relationship appears to be ungainly, it can be set up in
a spreadsheet to provide corrections even on the job site. At least
one manufacturer has incorporated this relationship in electronic
based moisture meters that allow selecting for a specific species
by code and temperature, and correctly interpreting the displayed
reading. Species correction coefficients for a range of commercial
species and species groupings (hybrids) are provided in Table 1.
Manufacturers supply meters for many areas of the world and
for many different applications. Therefore, it is common to find
meters that are pre-programmed with different correction factors than those described above. The references and material
listed above are relevant to Canadian conditions.
When sourcing or utilizing any moisture meter the user
must be careful to get information on how the meter has been
Figure 3. In-situ pins connected to moisture meter using leads (on left) and close-up of thermistor and insulated pins (on right).
16 Journal of Building Enclosure Design
]
1 -b
a
calibrated and what “on-board” calibrations are available for use
outside of its base line condition.
An example of the range of true moisture content for different
species and species groups is shown in Figure 4 (see page 18).
For accurate measurement and interpretation, the temperature should be measured with a separate instrument by inserting
a probe into the hole created by driving the moisture meter pins
into the wood. The influence of temperature on the uncorrected
meter reading is shown in Figure 5 (see page 18). Use of a
typical handheld temperature gauge for this purpose is shown in
Figure 6 (see page 18).
Moisture gradients
In most applications in the field, moisture is seldom distributed uniformly. In studs, wall plates or floor joists, particularly in
the exterior envelope where the greatest environmental differentials between inside and outside exist, there will be moisture
movement.
Consequently, it is necessary to assume that there are moisture gradients.
For lumber that is drying uniformly from all four faces and
from a high MC level, depending on the rate of drying, the
Table 1: Species correction factors for resistance type
moisture meters calibrated for Douglas-fir based on USDA
data for that species {from [10]}
Species
a-coefficient
b-coefficient
Sitka Spruce
0.853
0.398
Eastern Hemlock
Norway Spruce
Western White Spruce
Eastern White Spruce
Black Spruce
Red Spruce
Red Pine
Eastern White Pine
Western White Pine
Ponderosa Pine
Lodgepole Pine
Jack Pine
Alpine Fir
Balsam Fir
Western Red Cedar
Eastern Yellow Cedar
Trembling Aspen
0.904
0.702
0.828
0.702
0.820
0.723
0.730
0.821
0.969
0.849
0.835
0.749
1.070
0.900
1.019
0.922
0.910
-0.051
approximate average value is at about 1/5th to 1/6th of thickness
when measured on the middle of the wide face. Under mild drying conditions (say air drying) or a piece of under initial uniform
moisture, the distribution is assumed to be parabolic as shown
in Figure 7 (see page 19). The higher the rate of drying, the
higher the moisture gradient. In other words, the face of the lumber piece dries to a very low MC relative to the core.
Of course, if there has been subsequent wetting, the shell of
the piece of lumber will be wetter than the core and a reverse
distribution may be found. This alone may be of great assistance
in understanding the circumstances leading to the distribution of
moisture found in the assemblies being investigated.
Also, as the lumber acclimatizes in storage or in a building
structure, the high gradients expected immediately after kiln drying will no longer exist. Instead, gradients specific to the environment actually experienced will predominate. It is thus necessary
to understand the circumstances possible for the assembly being investigated and the likely history of the wood in the framing
when measurements are being done.
In field applications, it is important to consider the location
of the lumber being probed and its function. For example, a wall
stud is usually subject to a temperature differential across its
depth (in the thickness of the wall). It may be exposed to air in
the cavity on both faces, but not to air on the edges, especially
the outside edge.
When using a DC-resistance (pin) meter it is possible to insert the insulated pins to different depths to observe the change in
moisture with depth.
0.818
-0.621
0.818
-0.378
-0.024
0.793
0.556
-0.391
0.233
-0.545
0.467
-2.950
0.350
-0.455
-0.751
2.750
Hybrid Coefficients
Western Hem-Fir
0.838
0.693
Northern Alberta Pine
0.792
-0.039
Douglas Fir
0.838
Spruce (Canadian Maritimes) 0.792
Northern Alberta Fir
0.985
0.139
-1.300
0.693
Summer/Fall 2008 17
Figure 4. Figure showing the correction to meter readings for a range of species at a calibration temperature of 22.8°C.
Figure 5. Showing the effect of temperature on meter readings for an example species
(Douglas-fir).
Figure 6. Hand-held digital thermometer fitted with thermocouple probe to measure internal
wood temperature.
Touching the pins to the surface of the wood will give a reading that reflects the EMC of the wood under environmental conditions in that vicinity.
You need to penetrate the exposed layers of wood cells to
get to the material that accurately reflects moisture content in
the piece near the surface. As you probe deeper, you will get an
idea of that gradient.
Conventional symmetrical drying normally leads to a parabolic
gradient (as shown in Figure 7 as a dotted line) and the mean MC
will be found at a depth of about 1/5th to 1/6th of the thickness of
the lumber if insulated pins are used. For a 1.5 inch piece of lumber
(38 mm), that depth is about 0.25 to 0.3 inches (6 to 7.6 mm).
Not all cases involve symmetrical drying. For example the
bottom plate of a wall may have sat in a pool of water during
early construction. And because of contact with the subfloor will
have dried very slowly from that contact plane.
The gradient may well show greater and greater MC with
depth from the top face down to its bottom. To determine if
wetting has taken place, several readings should be taken. For a
symmetrical distribution at least two readings should be taken. If
only the edge of the lumber is accessible it is suggested that the
two readings be taken at 6 and 25 mm depth and averaged. Also,
if only the edge is accessible, readings can be taken at different
vertical positions from the bottom to the top face. This allows
18 Journal of Building Enclosure Design
taken to determine if a wet pocket is responsible for the high
reading.
Small wet pockets are not a concern as they will eventually
dissipate into the rest of the board and dry out. Wet pockets
may be found when lumber is initially dried, but by the time the
lumber ends up in a finished structure, the moisture gradients
will be significantly reduced. In practice, deleterious effects have
not been found by including wet pockets in lumber supplied; it is
usually only a matter of time before the local wet pockets dry to
the similar condition of normal wood.
High temperature Kiln Dried Wood
Normal maximum kiln drying temperatures range up to 160°F
(71°C) for a significant portion of the kiln schedule. Very high
temperatures cause a change in the basic structure of the wood
which results in a change in its resistivity. However, investigations
into the effect of high temperature drying, with temperature
ranging up to 212°F (100°C) or higher for a significant portion of
the kiln schedule have not been found to have a significant effect
[11].
Figure 7. Two possible moisture gradients, after kiln drying (dotted line), after rewetting
(solid line).
us to simulate readings that would have been taken at different
depths if the wide face had been accessible.
Wet pockets
Very briefly, certain species are prone to a condition referred
to as “wet pockets”. These prevent the establishment of a normal moisture gradient in lumber. The main softwood species
used for construction that are affected are balsam fir and subalpine fir in the Spruce-Pine-Fir group, and hemlock that is part of
the Douglas Fir-Hemlock marketing group. The problem is due
to a bacterial infection in the living tree which does not affect
wood strength or its color but does affect its liquid and vapor
permeability. The permeability is reduced to the point where,
wet pocket zones in a board may take 3 or 4 times as long to dry
as normal wood. The infection is usually not widespread in a tree
and therefore typically affects only portions of a board.
After a normal drying cycle of a kiln charge, it is possible to
find localized areas in a board cross-section that may have MC’s
as high as 30 to 50 percent MC while the rest of the wood is
well below the target MC, see Figure 8. If a high moisture
reading is obtained using a resistance based meter, at least 3
or 4 additional readings along the member in question should
Moisture content of treated lumber
CCA treated wood
Copper Chrome Arsenate (CCA) treated wood has been
the most commonly available pressure-treated wood used in
construction. This wood is dried and then pressure treated in a
water-borne solution of chemical. Consequently, the presence
of an S-DRY stamp on pressure treated lumber is not indicative
of the moisture content after treatment. The material is stored
Figure 8. Typical wet pocket in cross-section of a board from a species such as balsam fir or
western hemlock.
Summer/Fall 2008 19
at ambient temperatures or heated for a short time and the
chemical becomes fixed to the fiber in the wood and protects
the treated portions from decay. The treatment adds water to
the wood, but this is not normally considered to be a problem
for exterior uses. For use in a building, kiln drying after treatment (KDAT) should be specified.
The moisture content of CCA-treated wood, when used in more
severe conditions in the building envelope can be evaluated using
the same procedures as for untreated wood. CCA-C treatment
has been reported to be less conductive than for salt treatments.
The error for treated southern yellow pine was about 2 percent
MC in the range 12 percent to 25 percent [14].
ACQ and CA treated wood
Alkaline copper quat (ACQ) and copper azole (CA) have
largely replaced CCA treated wood for exterior and other locations. They contain more copper than CCA, and are more corrosive to unprotected fasteners. They require use of hot dipped
galvanized fasteners and connectors (or stainless steel). No information is currently available on the potential effect that these
treatments have on the moisture content readings by either resistance based or dielectric based moisture meters.
Sodium Borate (SBX) treated wood
Sodium borate treated lumber and sheathing has recently been
introduced into the market in Canada and the U.S. This is also a
water-borne treatment, but it is intended only for applications protected from rain. All borate treated wood should be specified as
KDAT. The treatment will also prevent decay and be instrumental
in reducing the risk of mould growth. A recent study available to
the authors has shown that the resistance based meter reading
was 2 percent to 4 percent higher over a 12 to 30 percent MC
range for treatments intended for controlling native termites, and
from 2 to 8 percent higher over that range for higher retention
treatments intended to control Formosan termites.
The apparent resistivity is strongly sensitive to the treatment
level and species, and until that data is published in its entirety
it is necessary to temper any readings taken on borate treated
lumber or panel products, recognizing that measured moisture
values can be considerable higher than actual moisture values as
shown in Figure 9.
Fire-retardant-treated wood
Fire-retardant-treated or FRT wood is produced by either
coating or pressure treating with chemicals. The majority of
fire-retardant-treated wood used in construction is strictly surface coated. The interior of surface-coated wood is essentially
unaffected and therefore the method of moisture measurement
is unchanged from that for untreated wood. It is important to
ensure that insulated pins in good condition are used to avoid
any electrical contact with the fire retardant. In pressure-treated
material, the presence of fire retardant within the wood will affect its resistivity and therefore a separate correction factor is
required. At present, there is insufficient information to suggest
how to interpret moisture meter readings in this situation. If
moisture content data on such material is required, cutting small
samples for an oven-dry determination is recommended.
In conclusion, while accurate estimation of moisture content
is difficult in wood having some types of treatments, it should
be noted that some of those treatments are done to protect
20 Journal of Building Enclosure Design
Figure 9. Approximate relationship between oven dried moisture and moisture meter readings
for borate treated Western White Spruce at room temperature at different treatment levels.
the material in high MC conditions and that, despite measuring
higher moisture than recommended for normal wood (even after correction for changes in resistivity), there is no justification
for assuming that the treated portion of the structure is at risk.
This does not mean that other portions of the structure are not
affected by the source of that moisture.
Moisture measurement in other wood
products
Oriented Strand Board [OSB]
OSB panels are produced by laying up parallel and cross mats
of wood strands having a wafer-like appearance. The adhesive
used is either applied in powder form or sprayed in liquid form as
the strands are tumbled in a large drum prior to lay-up in mats.
Lower density aspen and poplar are preferred for this product
because these strands can more easily be made to conform to
each other under heat and pressure. However higher density
species such as southern yellow pine have also been used successfully. The high temperatures and pressures used also result in
some densification of the material. Industrial wax is applied to the
wafers to allow better uniform adhesion of powdered adhesives
to the wafer surfaces. This also imparts some water repellency
to the finished product.
Due to the densification and the addition of wax and adhesive,
the bulk density of OSB is higher than that of wood or plywood.
The moisture content (dry weight basis) is about three to four
percent lower than for solid wood of the same species at the
same conditions. Limited testing was conducted at Forintek to
develop a correction factor for OSB. Existing temperature correction data for solid wood was used to develop corrections at
other temperatures. Correlation coefficients for use with the
previously noted equation in this paper were developed [a=
0.838, b=0.693]. It should be noted however that there is considerable variety in sources of supply and species used for this
widely used product and these results only provide a rough guide
for the correction that should be applied.
Finally, it should be noted that the calculation of bulk moisture
content includes the weight of adhesive and industrial wax that
is still retained after manufacture. The moisture content of the
wood fibers would be somewhat higher, closer to that achieved
by unprocessed wood. The addition of, say, 3 percent moisture
to the corrected bulk moisture content is one way to account for
these issues and to provide an estimate of the moisture actually
experienced by the wood fibers in these products.
Plywood
Plywood panels are laid up with parallel and cross-ply layers
of veneers that are rotary peeled from logs. After drying, sorting and grading, liquid beads of adhesive are deposited on each
sheet or width of veneer on their way to the lay-up station. The
pressure and temperature used by the presses in the production
of plywood are lower than those used for production of OSB resulting in less densification. The adhesive forms a mostly discontinuous thin film that alters the liquid permeability of the product
somewhat. The moisture reading obtained with a resistance-type
meter is based on the most conductive path of the veneer into
which the pins have been inserted. At high moisture levels, because of the possibility of liquid paths in the more open structure
of veneers compared with solid wood (caused by lathe checks),
somewhat higher than average readings may be obtained.
Because of the added mass of adhesive and slight densification,
the bulk density of plywood is higher than wood from which it
was derived. Consequently, at specific environmental conditions,
the equilibrium moisture content of plywood based on bulk density will be about 2 percent less (dry weight basis) than would be
achieved by the parent material based on oven drying determinations. More accurate readings can be obtained if care is taken to
insert the pins from a resistance-type meter into the same layer
of veneer. Grain direction has a small effect and it is advisable to
take the average of parallel and cross readings.
The species of veneers used in the core may not be the same
as that used on the faces. Consequently one is limited to using
species and temperature corrections based on broad species
groupings such as are provided in Table 1. Over the fiber saturation of plywood, the errors in estimation of moisture content are
far larger than in solid wood. In part this is because of moisture
gradients, and the makeup of the material.
Accuracy of estimation of moisture content using DC-resistance based moisture
meters
There are limits to the accuracy with which the moisture content can be measured by any electrical means. All handheld electrical meters (DC-resistance and dielectric) are not considered to be
reliable for measuring moisture content above the fiber saturation
point (25 to 30 percent). Given the discussion in earlier sections
dealing with a) species effects, b) temperature effects, and c) moisture gradients, an appropriate question to pose is what accuracy
can be achieved when you think you know everything you need to
know. The following example will try to answer that question.
In the study of moisture content of framing in houses under
construction, field inspectors selected cutoffs, or cut pieces from
longer lengths of framing lumber used for walls on buildings sites
in 10 population centers across Canada [4]. The pieces were from
2 x 4 studs usually, and cut to be at least 1.9 inches (50 mm) long.
They were bagged and shipped to the Forintek Laboratory in
Ottawa for analysis. They were pinned at two depths (shell
and core, at 0.37 to 0.98 inches (9.5mm to 25mm) into the
edge of each piece), oven dried to determine their mean
moisture content, and the species were identified. The meter
readings were adjusted for species and temperature for comparison with the oven dried values.
Nine species were identified, although individual species could
not be identified within the spruce genus on examination of the
wood alone and these were grouped together. A comparison
between the estimated and the oven-dried MC values for the
spruces is shown in Figure 10 below.
The regression of samples having less than 30 percent MC
had an R2 = 0.927, and a root mean square error of 1.52 percent MC. This implies that with the best of information (excluding specific species in the group) the estimate of possible error
over the range, roughly 10 to 30 percent MC, the true mean
moisture content is within 1.5 percent MC of the correct value
roughly 68 percent of the time. Over 30 percent MC (over fiber saturation) the scatter is considerable, although there were
only 40 specimens in that region. Estimating the average MC at
high levels of moisture is dubious—all one can say is that the
wood is wet.
It was noted that when the pine and fir samples were added
(N=391), for the 10 to 30 percent range, R2=0.835 and the RMSE
was 2.4 percent MC. The estimate of error in moisture content
above 30 percent was in the order of 8 to10 percent MC. Of course,
better results will be obtained if specific species can be identified.
Key points on the use of DC-resistance based moisture
meters:
• Care must be taken to ensue that moisture readings are obtained from sound, clear wood and special precautions should
be taken with species that are prone to wet pockets to not
presume general wide spread moisture on the basis of readings in one locale.
• Proper pinning depth is important to ensure a good estimate
Figure 10. Comparison between oven-dried MC and meter-adjusted measurements for 264
spruce samples from building sites across Canada.
Summer/Fall 2008 21
of average MC. Of course, due to expected moisture gradients these should be evaluated as the gradient may provide
information as to the source of wetting.
• Moisture meters can provide good estimates of the actual
moisture content of wood provided that moisture levels are
under fiber saturation (about 30 percent) and the species can
be identified and the temperature at the pinning location is
known.
• Moisture gradients must be investigated to help in determining the source of wetting if possible, and to assess if drying
to safe levels would occur without intervention, or if more
destructive investigation is warranted.
• Meters can be used on composite products such as plywood
and OSB. But much less information is available about the
variability of readings taken. In part this is due to the complexity of the materials and partly due to scarcity of the data.
normal calibration assumes the lumber has a typical parabolic moisture gradient and that the average moisture content is the property
of interest. This may not always be the case. Some meters are available that generate two selectable electric fields, one—typical for assessing the average moisture of lumber, and another—generates a
weaker field to assess the moisture of the near surface material in
lumber. Effectively this is an attempt to assess gradients. We do not
have experience with these meters as yet. Most of these meters are
heavily influenced by surface moisture content. A moisture gradient
involving either a very wet or very dry surface will cause MC estimates to be over or underestimated respectively.
As with DC-resistance meters, the limitations of dielectric moisture measuring technology should not be considered as a reason
to not take advantage of this technique. Indeed, meters combining
both functions have come on the market in recognition of both the
limitations and the capabilities of each type of instrument.
CAPACITANCE BASED MOISTURE METERS
While most of this paper has concentrated on the use of DCresistance type moisture meters, this is not meant to minimize
the potential for the use of meters based on dielectric properties
of wood. As noted earlier, some mills employ dielectric based
meters on line for all lumber produced, and with proper calibration accounting for the species and the moisture gradients typically present at the manufacturing stage, estimates of moisture
content can be made within +/- 2 percent of true levels [12].
For on site investigations, the value of a dielectric type meter
lies in the ability to use it as a scanning device to detect locations where higher than expected moisture contents may be detected. It is a nondestructive contact instrument in contrast to
the DC-resistance based moisture meters that must insert pins
into the material being assessed. By setting the threshold value
of a dielectric based meter in a location that is not expected to
be “wet”, one can then scan the surface of a wall to locate areas
that may be of greater interest to investigate carefully. By attaching the meter to an extendible pole, upper walls and ceilings can
also be quickly examined. In reality, based on this description,
a dielectric meter is an essential tool for pre-screening and the
DC-resistance based meter is essential for obtaining, to the extent that is possible, a good estimate of the moisture content of
the material being assessed and the distribution of that moisture
within the material.
Dielectric meter readings are affected by the temperature of
the wood but the correction is less than half of that required
for resistance based meters [12]. For pre-screening purposes, it
would not be necessary to attempt corrections. Things such as
meter application pressure, surface condition of the wood, and
the presence of knots do have a minor impact on meter readings.
If, however, the intent is to use this meter to pre-screen material
the effect of these variables can be neglected. The main variable which must be accounted for is specific gravity. Since specific
gravity varies between species this is usually referred to as a species correction. Specific gravity can be determined through a laboratory test but for most applications a species average from the
Wood Handbook (1) is sufficient. Many meters of this type have
the ability to be adjusted for the specific gravity of the material.
The prime drawback to the use of a dielectric meter is that its
GENERAL PROCEDURE FOR ON SITE INVESTIGATION
To assess the general moisture content of a stud in a wall, two
sampling locations with a moisture meter are recommended.
Readings taken at a level of about 11.8 inches (300 mm) and at
mid height, approximately (47.2 mm), should give a fairly good
estimate of the basic moisture content of the vertical members in
that elevation of the building, at that storey level see Figure 11.
Interior wall studs are more likely to be representative of
the lumber as it was delivered to the site and then dried somewhat in place. These are usually only enclosed with gypsum
wallboard and are not subjected to significant temperature gradients. As a result, drying is readily permitted and the moisture
content of interior studs is less critical to durability. Exterior
wall studs and plates are the more critical elements to evaluate,
since they are generally more exposed to the weather and are
constructed to be resistant to moisture flow.
The bottom plates are likely to be the wettest of the framing
lumber in the building and should be checked more rigorously.
These pieces should be checked for core and shell moisture content and at several points along their length. Headers, rim joists,
built up columns or other assemblies with a large mass of wood
are slow to dry when wetted. Boards in areas where drying is
22 Journal of Building Enclosure Design
Figure 11. Suggested approximate locations for meter measurements to obtain average
moisture contents in studs and wall plates. [13]
inhibited by impermeable flashing or peel and stick membrane,
should also be checked.
It is unlikely that high moisture conditions in interior wall
framing at time of installation will lead to conditions that
encourage decay. These walls generally dry rapidly because
there are few or no barriers to inhibit vapor transmission. The
major consequence of tolerating higher moisture levels in the
interior load bearing members is that more settlement and
shrinkage of the interior will take place relative to the exterior
shell of the building. This is not expected to be a significant
effect although the total shrinkage of the whole building must
be accounted for in the design of the plumbing and sewage
distribution system.
If the intent of the measurements is to assess whether it is
acceptable to proceed with the construction, it is recommended
that a minimum of 4 studs be evaluated in each exterior wall elevation. As far as the number of storeys that should be assessed,
in most cases (from our experience) the bottom storey will be
the wettest even though it will have been constructed first. A
small amount of ad hoc evaluation may be helpful to determine
where attention should be focused with regard to detailed MC
measurements in the building.
In summary, when it is found that higher than desirable moisture levels have been detected, adequate sampling is required
to provide a solid basis for a decision to delay construction or
undertake some additional measures. It is recommended that,
for the studs in any particular wall with moisture readings at two
depths at each location, measured at two heights, and for four
studs in the wall, a total of 16 readings be obtained. The same
level of sampling should be done for the bottom wall plates. This
should give the builder and assessor sufficient information to
form an opinion on the degree of additional drying that may be
required before proceeding. The builder and assessor can only
make decisions of this nature, at the time of inspection. It may
well be decided that significant portions of the framing can be
closed in and to only leave unfinished those sections which require longer natural or induced drying.
Interpretation of MC measurements in the field
The issue of high moisture content in construction lumber
is not new. Wood frame construction, as practiced for almost
two centuries now, has always had to incorporate measures to
mitigate the effect of moisture. Given the variability in climatic
conditions across North America and the large seasonal changes
experienced in northern climates, it is difficult to put forward a
general rule on what degree of wetness might be tolerable over
time. Judgment is needed, particularly with respect to the type of
construction, the scheduling and degree of protection provided.
Some factors that builders and inspectors may consider when
they encounter framing that exceeds code requirements are discussed below.
Species identification
The average person will not be able to recognize the species of a piece of lumber. Generally, wood anatomists can, with
the help of a magnifying glass, a penknife, and an examination
of a large enough piece with grain deviations and knots. Even
then some particular genus of spruce, for example, may not
be possible to identify without seeing the bark of the tree as
well. Where does this is leave the building inspector or forensic
specialist?
First of all, the grade stamps help identify the marketing
group, and in some cases the specific species being marketed.
For example SPF signifies the spruce-pine-fir group which includes up to 4 species of spruce, and an assortment of pines
and firs. When more specific or individual species are marketed alone this makes the task easier. Even so, this may take
some doing if grade stamps are not visible even if a portion
of a wall or assembly is exposed. In the event that nothing is
known about the material in the wall, looking at some other
portion of the house say the basement, where there may be
partitions and some exposed wood, may reveal what some of
the material was graded as. A shipment for floor joists would
not be a good indication as to the species group used in wall
assemblies simply because they come from larger trees and
may well have originated from another manufacturer/supplier.
Also, sometimes knowing the regional construction practices
and sources of supply can help pin things down. On the whole,
stud grade material is often used in constructing walls and, as
they are relatively over designed, there is less benefit from
and interest in marketing specific species. On the other hand,
framing lumber of the same size which is used in higher stress
applications such as roof trusses and wood I-joists may well
be sorted by species or at least be more predominant in one
species.
Accredited grade stamps for Canadian lumber are to be found
on the Canadian Lumber Standards (CLS) Accreditation Board
web site (Membership Information), and corresponding grade
stamps for lumber produced and graded in the U.S. are located
on the American Lumber Standards Committee, Inc. web site
(Accredited Agency List).
In a critical investigation, particularly one in which some destructive examination has been done to reveal the underlying
structure, grading agency inspectors can be called in to examine
and more accurately identify the species of lumber used in a particular structure.
Climatic factors
The climatic conditions are extremely important. Conditions
in most of the country will often favor the maintenance of
or promote drying toward an acceptable moisture level.
Unfortunately, because unfavorable conditions - either being
too wet, or too humid, or too cold can occur in all locations,
the builder must exercise caution. The weather conditions in
some areas are so unpredictable that protected construction
is the only way to lower the risk of delays. Undertaking construction practices that minimize the risk is another part of
the solution. For example, using exterior insulation changes
the thermal gradients and results in warmer stud cavities.
With judicious consideration of vapor resistance of materials
making up the wall, it is possible for excess moisture to dry
to the interior.
Type of wall system
Some completed wall systems are more amenable to drying
than others. Partially completed walls will be more amenable
to drying and this should be taken advantage of when possible.
Summer/Fall 2008 23
Many wall systems built in colder climates are built with a vapor
barrier located over the interior surface of the framing, just behind the interior gypsum board lining. Therefore the majority of
drying of moisture after the installation of the vapor barrier can
only take place toward the exterior. Advantage should be taken
of all conditions that could provide drying to the interior before
the vapor barrier is installed. The polyethylene vapor barrier
also serves to protect the gypsum board from moisture in the
wall. The paper faces are particularly vulnerable to supporting mould growth when exposed to high humidity. Drainage
capability behind the main weather barrier and the choice of
materials used affects the ability of a wall to dry out. This must
be left to the builders and designers to consider for each type
of system they employ.
Orientation
The orientation of walls affects their drying rate. North facing
walls and walls that are shaded from the sun by other buildings
can be expected to dry more slowly. These walls are of particular
concern and may have to be treated differently compared with
east, west or south facing walls that receive more solar energy. In
other areas, walls more exposed to wind-driven rain may require
special consideration.
The builder and inspectors must also keep in mind that loading of exterior cladding by rainwater can contribute to, or reduce
the ability of the backup wall to dry out. Stucco cladding is a wet
process and, until it has set, cured and been finished; it may reduce the ability of the inner wall to dry to the outside. A solar
driven moisture wave front toward the interior of the wall is not
unusual, but the effect can be minimized by use of a ventilated
cavity. Sequencing of construction in addition to location and orientation is critical when assessing the moisture content that can
be safely retained in the framing.
Indoor climate
It is not expected that interior conditions in northern climates will have much effect on exterior wall performance when
a vapor retarder is installed and an air barrier system is used to
minimize air movement. However, if these construction details
are not properly addressed, the moisture content of the lumber
framing becomes more critical. The level of seasonal moisture
storage may be safe for a building with a lesser initial moisture
content. Should the initial moisture content be high at time of
closing, the addition of further moisture might prevent drying in
a timely fashion.
Air conditioning in the summer can do much to reverse the
flow of moisture in a wall. Here, it almost goes without saying, its
makeup and design will affect the tolerance of the wall to these
conditions.
Key points on the factors that influence interpretation of field
measurements
• Bottom plates are likely to be the wettest of the framing lumber in the building and should be checked more rigorously.
• For vertical members, meter readings should be taken at various heights and depths to assess average MC and moisture
distribution.
• There is no hard and fast rule to recommend an upper limit
of moisture content in construction materials in the standing
frame to prevent deterioration because so many factors are
involved.
• The local climatic conditions, particularly wind-driven rain,
can affect the likelihood of drying in a reasonable timeframe.
• The type of wall, its materials and design, ultimately affect the
decision as to what must be done in cases where excess moisture exists.
• The orientation of walls in relation to solar gain, and in relation of the prevailing direction of wind-driven rain, plays a major role and should be accounted for in design and predictions
on time required before closing.
• The indoor environment and whether or not it is air-conditioned must also be considered.
SUMMARY
With regard to the use of DC-resistance based meters:
• DC-resistance based moisture meters can provide good estimates of the actual moisture content of wood when both the
temperature and the species are known.
• Moisture gradients can also be readily assessed using resistance-based moisture meters equipped with insulated pins.
• DC-resistance meters are the most practical and versatile for detailed testing of construction lumber that is in
place.
• DC-resistance meter readings must be corrected for the effect of wood temperature and species, in order to get the
most accurate predictions of MC.
• Typically they only provide reliable results up to fiber saturation, say 30 percent.
24 Journal of Building Enclosure Design
• Proper pinning depth or readings taken at various depths is
important to ensure a good estimate of the average MC for
the cross-section.
• Care must be taken to ensure that reading are obtained from
sound, clear wood and special precautions taken when dealing with species prone to wet pockets.
• For solid wood treated with some preservatives or fire-retardants there is an effect on the meter readings. However there
is limited information available on how to apply corrections to
those readings.
With respect to the use of dielectric based moisture
meters:
• Dielectric meters are useful for scanning or pre-screening areas where more moisture exists and are a useful survey tool
in conjunction with DC-resistance meters.
• Specific gravity of the material being scanned is the prime factor influencing the meter readings.
• The effect of temperature of the wood is less than half of that
effect for DC-resistance based meters.
• Moisture gradients cannot be assessed accurately using dielectric meters.
• Both types of meters can be used on composite products
such as Plywood and OSB.
• Little is known on how much effect preservatives or fire retardants have on dielectric moisture meter readings.
Finally, with respect to the interpretation of the severity of moisture
readings found:
• The 19 to 20 percent code limit is only a guide for lumber
producers for drying wood so that it can be used in construction with low risk of mould growth. Further drying is expected in place. This was based on experience and construction
practices that extend back to the 1800s.
• The grading rules specify a 19 to 20 percent MC limit for drying but allow up to 5 percent of a load of lumber to be over
that value. This tolerance for “off spec” pieces acknowledges
that there is variability in MC from piece to piece in the kiln
charge due to drying conditions and natural variability in the
material. Additionally, there are high moisture gradients in
the lumber right after kiln drying that may partly equalize in
storage.
• Construction that uses wood framing having high moisture
content needs to involve practices that maximize drying of the
structure and should involve monitoring of moisture content
at critical locations in the structure.
• Monitoring the moisture content of building materials is an
emerging need in construction. Accuracy is perhaps less important than identifying when a problem exists.
• Having both DC-resistance and dielectric meters available
to inspectors is an effective way of screening for moisture
problems. Probably also needed is a temperature meter
and RH meter. Flexibility in the capability of tools is very
desirable.
Donald Onysko works for DMO Associates in Ottawa, Ontario.
Christopher Schumacher works for Building Science Corporation
in Waterloo, Ontario. Peter Garrahan, works for FPInnovations,
Forintek Division, in Ottawa, Ontario.
References
[1] Wood Handbook: Basic Information on Wood as a Material of Construction with Data for its Use in Design
and Specifications. Prepared by the Forest Products
Laboratory, Forest Service, United States Department
of Agriculture, [Slightly Revised 1940], Washington,
DC.
[2] Wood Handbook: Wood as an Engineering Material.
1999. Forest Products Society Madison WI.
[3] Zabel, R.A. and J.J. Morrell. Wood Microbiology: Decay
and its Prevention. Academic Press. San Diego CA.
[4] Garrahan, P. J. Meil and D.M. Onysko. 1991. Moisture
in Framing Lumber: Field Measurement, Acceptability
and Use Surveys. Forintek Canada Corp. report for
Canada Mortgage and Housing Corporation
[5] Bramhall, G. and M. Salamon. 1978. Combined speciestemperature correction tables for moisture meters.
Info. Report VPX-103 (revised), Forestry Directive,
Environment Canada, Western Forest Products Laboratory.
[6] Cech, M. Y. and F. Pfaff. 1975. Moisture content correction tables for resistance-type moisture meters. Report
7. Dept. of Environment. Can. For. Serv.
[7] Mackay, J.F.G . 1984. Assessment of accuracy of species-temperature correction tables for resistance-type
moisture meters. Forintek Canada Corp. Vancouver,
B.C.
[8] Pfaff, F and P. Garrahan. 1986, New temperature correction factors for the portable resistance-type moisture meter. Technical Note. Forest Products Journal.
36(3):28-30.
[9] James , W.L. 1963. Electric moisture meters for wood.
USDA Forest Service. Forest Products Laboratory. Res.
Note FPL-08, Madison, WI.
[10]Garrahan P. 1988. Moisture Meter Correction Factors.
Forintek Canada Corp. Proceedings of a seminar on
“In-grade testing of structural lumber”, held at USDA
Forest Products Laboratory, Madison WI.
[11]Garrahan P. 1987. Moisture Meter Correction Factors
for High Temperature Dimension Lumber. Forintek
Canada Corp. report to the Canadian Forestry Service.
[12]Garrahan P, and V. Lavoie. 2005. Evaluation of Factors
Affecting Moisture Estimates from a Dielectric Type
Moisture Meter. Forintek Canada Corp. paper presented at the 2006 IUFRO meeting in Beijing, China.
[13]CMHC. 2001. Guidelines for On-Site Measurement of
Moisture In Wood Building Materials. Forintek Canada
Corp. Research Report prepared for CMHC
[14]Richards, M.J., “Effect of CCA-C Wood Preservative
on Moisture Content Readings by Electronic-Type
Moisture Meter,” Forest Products Journal, 40(2):29-33,
1990.
[15]Zelinka S.L. and D.L. Rammer. 2006. Electrochemical
method for measuring corrosion of metals in wood.
WCTE 2006- 9th World Conference on Timber Engineering. Portland OR.
Summer/Fall 2008 25
Feature
Energy Efficiency and
Durability of Buildings at the
Crossroads
BACKGROUND
A few years ago, the American Institute
of Architects (AIA) and the National Institute of Building Sciences (NIBS) agreed to
work together to organize Building Enclosure Councils (BECs) in cities across the
United States in an effort to encourage
the exchange of technical information and
know-how on the best practices of building enclosure design. As a result of that
agreement, BECs, organized as committees of state or local components of the
AIA, now exist in 21 U.S. cities. Further,
a memorandum of understanding with the
Canadian National BEC, executed at the
2008 AIA convention in Boston, provides
for Canadian collaboration in the information exchange effort.
The first Building Enclosure Science
and Technology (BEST 1) conference
was hosted by BEC and AIA Minneapolis
in June 2008. The conference, with the
theme of “Energy Efficiency and Durability
of Buildings at the Crossroads,” provided
a wakeup call about both the deficiencies and the creative opportunities that lie
ahead for the building design community
in responding to a changing world in which
buildings play a significant role in the use of
energy (as well its impact on U.S. security,
the balance of payments and the viability of
the U.S. economy).
This paper is an outcome of BEST1,
and it reflects the perceived need for the
Building Enclosure Technology and Environment Council (BETEC) of NIBS to
outline the current state of affairs. It is one
thing to specify that buildings achieve certain efficiencies; it is quite another matter
for that outcome to become a reality. This
is where practitioners come in as they are
the “doers” that make things happen. It is
expected that through the BEC network
a greater awareness of the technological
successes achieved and lessons learned
from failures in building system design can
impact future designs and convert design
intent into reality.
INTRODUCTION
The building industry is at a crossroads
and the question is, where do we go from
here? The “green” train has left the station
but the tracks are still being built. At the far
end there is an AIA commitment to achieving a 2030 carbon neutral future (and improvement in the existing building stock).
At the beginning, just outside the station,
there is a lot of good will but also a realization that the majority of existing highly
inefficient buildings will be with us well beyond 2030. There is a chasm that must be
bridged if that goal is to be achieved and
there is confusion on how to accelerate
the process of renewal.
All generally agree with the United Nations report that states:
The good news is we have got a
huge source of alternative energy
all around us. It is called energy conservation, and it is the lowest cost
new source of energy that we have
at hand. . . . Clearly saving energy is
like finding it.
Past successful programs for advanced
building design reveal that only “a systems approach” will achieve energy-saving goals in the future. We are past selling magic new materials and miraculous
one-issue solutions. Every building, old or
new, needs to be treated as an organism
in which every component is a piece of
the puzzle. Quick-fix efforts devoted to
only one or even several components in
the building enclosure, at best, probably
will not achieve sufficient energy savings
and may actually cause other problems.
Whether one changes only one component or rehabilitates the whole building,
effective approaches require advice from
experienced practitioners of all types. The
green value of actions is determined by the
resulting building performance, not by the
perception that an action is green.
Although the process for assessing the
success of energy-saving approaches is essentially the same for houses as for large
office buildings, the need for mock-up and
commissioning tests and the involvement
of the full design team in review of energysaving elements is emphasized for large office buildings. This paper describes both the
current status of building enclosure design
and how large potential energy savings can
Summer/Fall 2008 27
be achieved through the integrated design
of new buildings and the rehabilitation of
existing buildings. Included are comments
concerning the interrelationship of energy
efficiency, building durability, and the quality of the indoor environment.
The construction community is at a
crossroads and the stakes are high for
making the right choices. The operation of
buildings is recognized as a major component of energy use in North America. Building science has addressed this concern by
making great progress in our understanding
of concepts central to energy performance
of buildings. We can now offer a breadth
of proven approaches along with products
developed by industry to meet high performance requirements. At the same time,
our vision of buildings has ceased to be
valid. In order to move forward, we need a
new vision that will improve building energy efficiency, extend the building lifecycle,
and improve economic competitiveness by
putting savings from energy efficiency to
more productive uses. This vision cannot
be achieved without broad acceptance by
the entire construction community including building owners, investors, and financiers, as well as designers, engineers and
constructors.
To set the stage, the following topics
will be addressed briefly:
• Our carbon footprint—the scope of
current building energy use;
• Past changes in design practices and use
of energy;
• The current approach to design of the
opaque portion of building enclosures;
• Fenestration and its potential for minimizing or maximizing solar gains;
• Rehabilitation of existing buildings; and
• New building design.
OUR CARBON FOOTPRINT
Whether or not one agrees with the
direct link between CO2 increases in the
atmosphere and global climate change, our
carbon footprint is a convenient measure
of how we use energy generated from
combustion of fossil fuels. Because we
depend on other countries as sources of
much of our fuel, energy security is another priority, which has even greater precedence in the minds of some. Use of noncombustion energy sources such as wind
and solar power can lower our total carbon footprint, but are only effective when
28 Journal of Building Enclosure Design
combined with substantial increases in energy performance of buildings.
Reported statistics concerning carbon
footprints vary because some researchers
include the embodied energy in materials
and transportation whereas others consider
only the part that relates to the energy use
of the physical building and its occupancy.
One author claims that the average carbon
footprint per person in the United States is
33 lb/day, in California is 18 lb/day, and in
the city of Los Angeles is 8.5 lb/day. These
numbers are examples that demonstrate
how much the carbon footprint can reflect
both climate and occupancy. Most of the
carbon dioxide produced in buildings (3050 percent) results from the use of energy
for space heating and cooling, for appliances
(up to 20 percent), and for water heating
and lights (10 percent each). The total CO2
emissions from buildings, transportation,
and industry in the United States are currently estimated to be the same level as
those of China.
What about energy sources? Coal is plentiful in the United States, but coal consumption results in emissions levels two to three
times higher than those produced by other
fuels. Carbon capture and sequestration can
reduce carbon dioxide by 70 percent making coal a potential major transitional energy
source (including its transformation into liquid fuel), but these measures require heavy
investments and are not yet proven at a scale
that would begin to address the emissions
envisioned in the future. Wind harvesting
can be used only in limited locations and only
in conjunction with other base load energy
sources. Photovoltaic (PV) energy, although
still expensive, has a bright future but it requires improvements in the electric grid
and significantly reduced costs. The current
electric grid has a low efficiency. A future
economy involving a large number of plug-in
cars and thousands of PV installations would
require a smart distributed grid.
This brief overview of energy sources illustrates the dilemma. Many proposed “energy solutions” result in equal or greater carbon emissions (coal, coal to liquid, tar sands).
It is also evident that efforts to achieve energy
security and potential man-induced climate
change are coupled and proposed solutions
will need to have a positive impact on both.
If supported effectively, such solutions could
create a win-win situation for market-driven
technologies.
Thinking that changes in the supply side
of energy—involving any mix of coal, nuclear, ethanol from corn, oil sands, coal to
liquid transformation, or even hydrogen—
will fill our future energy needs may lead
us to an expensive dead end. Pushing one
technological solution is a traditional way of
increasing the energy supply without considering the demand side. We need to realize that the potential for reducing building
energy use is widely underestimated and is
the key to reducing overall energy demand.
In effect, by pursuing an aggressive energy
efficiency campaign dealing with both new
and existing buildings, it may be possible to
reduce the demand side to a level at which
many expensive alternative energy sources
will not be needed.
If we consider the passive energy savings measures available today to rehabilitate old buildings as well as those energy
efficiency measures now available for new
buildings, the picture is optimistic. However, if alternate energy supplies are to
be sufficient to meet the nation’s growing
needs, we need to initiate broad programs
for the “energy upgrading” of most of our
existing buildings and enact high energy efficiency standards for new buildings.
The figure on page 29, developed with
poetic license, represents the potential
impact of several supply side perspectives
compared with one massive demand side
option.
While the media talk glibly about the use
of renewable energy, they do not realize
that this approach requires very efficient
use of all energy from all sources. Renewable energy sources still represent only a
drop in the bucket given the gross inefficiency of today’s buildings. The construction and operation of buildings consumes
40 percent of the total energy used in the
United States whereas the transportation
sector uses only about two-thirds of the
energy used by buildings (or 27 percent of
total energy). Buildings also consume 68
percent of all electricity, which results in
the production of 750 million tons of CO2
(i.e., 38 percent of total U.S. production
of carbon dioxide and 49 percent of U.S.
production of SO2).
Average energy use by commercial
buildings in 1990 was 315 kWh /m2 but it
has declined steadily since that time, reaching 250 kWh/m2 in 2002. Note, however,
that this was equivalent to the energy use
of commercial buildings in 1920—in other
words, a masonry building without insulation built nearly 100 years ago consumed
as much energy as a shiny, glass-clad building constructed today!
This, of course, says nothing about the
increase in energy-consuming functions of
modern buildings. In contemporary office
buildings, the office equipment and computers use 10 percent of total energy but
lighting uses 28 percent. A layman, who
accepts that in 1920 people also used lights
(and probably less efficiently than now)
and who understands that we now employ improved thermal insulation, thermal
mass, air barriers and many other energy
saving measures, understandably would be
puzzled as to why we do not use much less
energy than in the 1920s.
This is the energy situation in which we
find ourselves. Some have proposed societal goals aimed at achieving carbon neutral
new construction by 2030, but to see how
this can be accomplished, we need to understand the changes in building construction that took place in the past 60 years.
REVIEW OF CHANGES IN
BUILDING CONSTRUCTION AND
THE ROLE OF BUILDING SCIENCE
Some changes that have occurred in
residential construction are described below followed by identification of the corresponding changes in the construction of
commercial and institutional buildings.
Control of heat, air, and moisture
movement in residential walls
Prior to the 1930s, walls often were not
insulated even though roofing felt was used
as sheathing paper, walls were very leaky, but
the use of building paper weather barriers, as
distinct from roofing materials, soon became
the rule. The building paper was placed on
the external side of the wall sheathing to
impede the movement of air and intrusion
of rain behind the cladding while permitting
some moisture to permeate to the outdoors.
To improve thermal comfort, wall cavities
were filled with insulation—first using wood
chips and other available natural materials,
sometimes stabilized with lime, then shredded newsprint, and eventually mineral fiber
and fiberglass batts.
Meanwhile, scientists observed that the
presence of thermal insulation in the wood
frame cavity lowered the temperature on
the outer side of the cavity, leading to a
higher potential for vapor condensation
that, in turn, was found to be detrimental
to the durability of the wall and the siding.
Vapor barriers were introduced to reduce
the flux of vapor coming from the warmer
indoor environment and to alleviate condensation problems. A practical unit of permeance describing a typical and acceptable
level of vapor flow retardation was introduced and named 1 perm (57 ng/m2 s Pa).
Effectively, the 1930’s-built house featured a paper-based water-resistive barrier (WRB) capable of changing from a water vapor retarder when dry to a breather
when wet because the paper acted as a
smart water vapor retarder that changed
its vapor permeability with moisture content. However, this WRB did not eliminate
the airflow through the wall. The air flow
helped to dry the moisture that condensed
on the cold side of the thermal insulation.
There was also the large moisture buffer
capability of sheathing planks, wood frame,
and insulation. Interior finishes were largely wet applied plaster. Finally, the pace of
construction was slow enough to allow the
building to dry and settle before the final
coat of plaster was applied.
Following World War II, wood boards
were replaced by plywood panels in wall
sheathing. During the 1970s waferboard,
and subsequently oriented strand board
(OSB), came to dominate the sheathing
market. The use of paper-faced gypsum
panels for the interior finish also emerged
during this evolution to reduce construction time. Incidentally, use of “drywall” reduced the construction moisture load and
the use of panel sheathing materials minimized air infiltration. The use of interior
polyethylene vapor retarders continued
this trend but also inhibited the ability of
walls to dry to the interior, and moisture
tolerance declined. Despite this use of materials that were progressively more susceptible to moisture, these materials performed adequately when properly used.
Nevertheless, to perform adequately, drying capability to the outside was critical in
this situation.
More recent increases in levels of thermal insulation have further reduced the
drying capability of walls such that deficiencies, such as leaks at windows or cladding
penetrations, may now result more easily
in moisture-originated damage.
Recent acceptance of the concept of
drain screen walls that allow rain water to be
drained from the space behind the cladding
has the potential to cause severe problems.
When water is delivered behind the cladding (and often behind the exterior thermal
insulation), a portion of it is retained on the
drainage medium, both the surfaces of the
cavity and the joints of panels. Despite the
perceived ability of these walls to drain down
to the flashing, water will evaporate and be
redirected by reverse thermal gradients to
the inside of the wall. To avoid this, one can
use a WRB with high resistance to water vapor but this, in turn, will further reduce the
drying ability from the inner wall.
In summary, the following major changes in wall design that reduce the moisture
tolerance of residential walls dramatically
have taken place over the past 60 years:
Summer/Fall 2008 29
• Increased levels of thermal insulation;
• Increased level of water vapor
resistance;
• Increased air tightness of the walls;
• Reduced ability of walls to dry;
• Reduced moisture buffering capability;
• Introduction of more moisture sensitive materials; and
• Allowing drainage from the wallwindow interface to enter behind the
cladding and exterior insulation.
can only be done if there is equal attention
is paid to indoor environmental and HVAC
considerations. Like the R2000 program in
Canada, the Energy Star program of U.S.
Environmental Protection Agency (EPA)
and the Energy Efficiency Building Retrofit
Program, a project of the Clinton Climate
Initiative (CCI), are good examples of
programs designed to reduce energy consumption in new and existing buildings by
specifying performance requirements.
The beginning of high-performance
housing in North America
Prior to the 1970s when energy security
became an issue, society was not very concerned about whole building performance.
The oil supply crises in the early 1970s, however, forced society-wide discussion of longterm global energy security and supply and
stimulated the introduction of energy conserving housing programs in Canada and the United States. These programs, in turn, affected
the construction of conventional homes. Airtight building enclosures were needed which,
in turn, required mechanical ventilation. Highefficiency heating devices were introduced
that modified air flow patterns in buildings
or eliminated the need for chimneys and this
raised a new concern—the need for an air redistribution system within the house. At that
point, interaction of the building enclosure
with the heating, ventilation and air redistribution system in the occupied space became
part of the builder’s design framework and
phrases such as “building as a system” were
used to describe the approach taken.
In summary, today we have the technology to achieve reliable design of building
enclosures to control heat, air, and moisture transport but we also realize that this
Changing the scale—commercial,
institutional and other large buildings
While residential building designs can
be suitably replicated in similar climatic
zones, large buildings are often unique
designs. There are great functional differences between different building uses—
office buildings, warehouses, laboratories,
hospitals, etc—and their energy use reflects that diversity. However, the heat,
air, and moisture transport physics remain
the same for all structures.
Air flows (infiltration and exfiltration)
are important to both energy efficiency
and building durability. The specific aspect
of air flow that relates to energy and durability is the moisture-carrying capability
of air, which is much more significant than
water vapor diffusion. Air movement also
can drive rain penetration. Air movement
occurs when there is connectivity between areas with different air pressures.
There are many causes for air pressure
differences (e.g., wind creating pressure
on one side of a building and suction on
the other side of the building). Pressures
due to stack effect arise from temperature
differences between indoor and outdoor
spaces as well as within a building itself.
30 Journal of Building Enclosure Design
The use of mechanical equipment such as
local exhaust fans in bathrooms, kitchen
fans, and heating and cooling equipment
also can create pressure differences.
Air carries outdoor pollutants as well
as those generated within the building enclosure. Mold spores from basements and
attics and those growing on paper-clad drywall on the interior of walls can be carried
into the living spaces. Consider one example: a typical office building might use a ceiling return plenum for air distribution systems. Steel stud exterior walls have internal
interconnected cavities and the drywall
finish typically ends at the level of the plenum. This condition provides uncontrolled
connectivity between those wall cavities
and the ceiling space. In other words, many
commercial buildings are designed with
unlimited possibilities for air flow from any
indoor space to any other space.
In effect, an airtight building enclosure
is needed for the following reasons:
• To reduce the amount of uncontrolled
air flow through building cavities and
its possible effects on the hygrothermal performance of the enclosure
and, especially to reduce the risk of
excess moisture being deposited in the
construction.
• To reduce the amount of volatile organic compounds (VOCs), particulates,
and mold spores carried from the
outdoors or from construction materials into the indoor space.
• To reduce the amount of heating and
cooling required by unconditioned air
entry.
The need for air pressure control in
buildings
As long as buildings were leaky and
poorly insulated, the effect of HVAC systems on induced air pressure and on the
durability of the enclosure was not significant. There was no need to understand air
movements in the building other than to
know that they provided a necessary supply of fresh air. This is not the situation
today. Now we require well-insulated,
airtight buildings in which the indoor environment contributes to livability. The
key to achieving these goals is to appreciate that air pressure fields have an important effect on the performance of building
enclosures; therefore, understanding air
movements in buildings is a necessity. Air
For technical people, every green building—indeed every building—must address many different aspects of
performance such as energy efficiency durability and build-ability, health and comfort of occupants (indoor environment), fire resistance, acoustics and affordability. This is not necessarily in agreement with public perception.
pressure differences, however small and
difficult to measure, must be determined
to establish the performance of the building as a system. This is probably one of the
key reasons for a fundamental revision to
many assumptions that have developed
over the years. Air transport control is
now recognized as the least understood
issue in the design of building enclosures.
While the need for air tightness is now well
recognized, achieving it in practice is still a
challenge. Rain penetration and the influence of air penetration remain the most
important issues to be handled in building
enclosure design.
Air barrier systems are required for the
proper performance of building enclosures
in all climates. Ensuring continuity of the air
barrier plane over 100 percent of the exterior surface is a key requirement for air
flow control by the building enclosure. Air
barrier continuity must be checked both
during the design review and (by commissioning) during construction.
WHERE ARE WE TODAY WITH THE
OPAQUE PART OF THE BUILDING
ENCLOSURE?
For a building to be truly sustainable,
the designers must address many different aspects of performance such as
energy efficiency, durability, constructability, health and comfort of occupants
(indoor environment), fire resistance,
acoustics, and affordability. This statement, however, does not necessarily
reflect public perceptions regarding sustainable design. In a 2007 survey, 41 percent of all respondents defined a “green
building” as one with a specified percentage of green materials and 46 percent stated that “green buildings” must
follow criteria established by a national
program. There is also a general perception that a “green building” will also be
energy efficient.
While the term “green buildings” has
become a buzzword for environmentally
driven impulses, a definition is needed for
performing a cost-benefit analysis. To avoid
ambiguity in the use of words like “green” or
“sustainable,” the term “high-performance
building” is preferred as it is defined in the
Energy Policy Act of 2005 as follows:
The term “high performance building”
means a building that integrates and
optimizes all major high-performance
building attributes, including energy
efficiency, durability, life cycle performance, and occupant productivity.
A consequence of this definition is that
the concept of “green materials” must be
expanded to recognize the importance of
“high performance assemblies.” For example, a bitumen-based self-adhering flashing
would not meet the public perception of
a “green material.” However, when properly applied, bitumen flashing tapes are key
components in durable, airtight assemblies.
Evaluation of systems, not materials
It is important to place emphasis on the
performance of the building and built assemblies instead of merely on the materials used in those assemblies even though
dealing with materials is easier. Building
codes and standards always ascribe a specific function to a specific material because
this is the only way that a prescriptive code
can work. Water resistive barriers (WRBs),
water vapor retarders, air barriers, thermal barriers (fire), and rain-screens are all
items in which functions and materials are
mentally coupled; however, a material
(e.g., closed-cell spray foam) also can function as insulation, a rain-screen, a WRB, a
water vapor retarder, and an air barrier.
The outcome of an architectural design
is modified by interactions between different materials and the trades involved
in installing them in an assembly. Architectural design and construction are holistic
processes that involve highly specialized
Summer/Fall 2008 31
We are past selling magic new materials and miraculous one-issue solutions. Every building, old or new, needs
to be treated as a system in which every component is a piece of the puzzle. Quick fix efforts for one or more
components in the building envelope, at best, may not achieve enough, and at worst, may cause damage. This
requires advice from experienced practitioners of all types.
people from multiple disciplines, and an
important issue is how they collaborate
during this process. This aspect of design
is so important that we stress the importance of mock-up evaluation and ongoing
commissioning as separate activities in the
construction process.
This is to ensure that the design concept is constructible and that all the building
trades learn how they must collaborate to
achieve the intent of the design.
So far we have established that the future
belongs to high-performance buildings. Let
us now review the critical components of
the matrix called, for simplicity, the “HighPerformance Value” of a building.
Key components of “high performance
value” during the design and construction of buildings
The key components of “High Performance Value” during the design and construction of buildings include:
1. Designing for durability.
2. Designing for energy efficiency and
efficient use of materials in terms of:
a. Separating ventilation/air distribution and heating/cooling systems.
b.Using instantaneous or integrated
hot water systems.
c. Increasing the use of day lighting
technologies and controls.
d. Improving the indoor environment
32 Journal of Building Enclosure Design
(with view to occupant health and
productivity).
e. Achieving design flexibility (i.e.,
lower costs associated with space
reconfigurations).
f.Re-using of materials in building
enclosure systems.
g. Designing from cradle to grave (i.e.,
considering whether the existing
components can be used in nextgeneration buildings).
3. Designing to be efficient enough to
justify economic use of renewable
resources in terms of:
a. Developing better tools for building
enclosure performance evaluation.
b. Improving control over inter-zonal
and interstitial air flows.
4.Laboratory or field testing of mockups of building enclosures for commercial buildings.
5.Using the commissioning process as
a part of the design and construction
process (from design intent through
the construction period and including
some post occupancy tests) by:
a. Conducting a trouble shooting
study of design drawings as the first
step in commissioning.
b. Testing air flows during
construction.
c. Testing air quality of occupied
space after occupancy.
d. Verifying predicted energy performance parameters against actual
building data.
Number one in the high-performance
value matrix is the issue of durability (longterm performance). If one extends the
service life of a building by, for example, 20
percent over that of typical construction,
one reduces life-cycle costs. In this process, the direct savings of replacement
and energy can provide multiple benefits
to owners.
The second critical consideration is to
increase all possible passive energy efficiency measures that lead to energy savings before progressing to active measures
that address energy utilization. Passive
measures often are neglected even though
they offer the most value for the invested
money. These measures include:
1. Simple building shape and mass placement that respects the climate (saves
capital and energy);
2. Increased air tightness (cost little,
saves lots);
3. Increased insulation values and
reduced thermal bridging (costs but
saves energy); and
4. Improved windows (increases capital
cost but saves operating cost) or
reduced window area (saves capital
and operating costs but may limit
daylight).
Economical solutions that can be applied to the supply side of the energy equation include use of:
1. Free pre-cooling with air distribution
systems.
2. Solar air preconditioning.
3. Geothermal preconditioning.
4. Solar hot water (often third party
financed—leased).
More complex technical measures that
can be employed include:
1.Radiant cooling.
2.Heat and energy recovery ventilators.
3. Diagnostics for malfunctioning systems
or components in service.
4. Dedicated ventilation air systems.
5. Brushless DC motors.
6. Small centrifugal compressors.
7. Micro-channel heat exchangers.
While these examples highlight some
of the current solutions used in highperformance buildings, they also shine a
spotlight on the bigger picture of progress needed. With a high level of thermal insulation in the enclosure and better windows, we would eliminate the
need for perimeter heating. High-performance building enclosures also can
change the HVAC and lighting systems
needed—that is, they can dramatically
reduce thermal loads, and encourage
the use of distributed HVAC systems
while also reducing electric lighting demand by effectively using daylighting.
There also is a trend toward use
of multifunctional building enclosures.
Dynamic envelopes can be used to
pre-heat or pre-cool indoor air and,
by using filters and dehumidifiers,
these enclosures can modify the indoor environment. Advances in glass
and window technology permit the use
of increased daylighting. With reduced
thermal loads, several technologies
previously discarded in research are
becoming more economically viable.
Coming back as significant improvements to the technology mix are use of
the effects of thermal mass and phase
change materials even though they are
climate-dependent.
FENESTRATION IMPACTS ON
BUILDING ENERGY
CONSUMPTION
It is estimated that windows account for
about 10 percent of total building energy
use. The traditional view of the high negative energy impact of windows in buildings
contrasts with the impressive progress in
window technology and systems that has
taken place in recent years.
Vision of window research—moving
windows from energy losers to energy suppliers
To achieve the goal of making windows
energy suppliers in cold climates one, must
reduce the overall U value (increase the
R-value and improve the thermal performance) enough that the solar gain can exceed the heat loss.
This implies that windows with a high
R-value and a moderate solar heat gain
coefficient (SHGC) should be used in cold
climates. In hot climates, the energy flows
are dominated by solar gain which is highly
variable depending upon climate, latitude,
season, and orientation, and needs vary—
i.e., cooling load controls vs. daylight admittance and view vs. glare control. Thus, in hot
climates as well as in mixed climates, static
control needs to be replaced by dynamic
control of solar gain. This approach should
drive design strategies and technology for
the near term. In the more distant future,
windows should become even greater net
energy suppliers by becoming more fully integrated with photovoltaic capabilities.
Highly insulated window systems will
employ such technologies as aerogels, vacuum glazing, low-E coatings, gas fill, and improved thermally resistive frames. Dynamic
solar control may include conventional dynamic solar shading systems such as roller
shades or blinds or can involve operation of a
glazing layer with a reversible optical switch
from high to low transmission. Suitable
technologies include active electrochromic
glazing (requires wiring) or passive thermochromic (reacting to glass temperature),
photochromic (reacting to sunlight intensity), etc. Field tests with prototype electrochromic windows were started in 1999 and
these technologies are now commercially
available. The 2030 “ideal” window is expected to have an R10 insulating value and
variable solar control and, in most climates,
will provide a net winter energy gain and 80
percent saving in cooling.
In today’s residential market, 95 percent
of the windows sold are double-glazed and
more than 50 percent have a low-E coating. Obviously this represents substantial
progress from 1973 when single pane windows dominated sales with double glazing
capturing only a small market share.
The simple comparison shown in the
images on page 31 stresses the fact that
today’s cost-effective technology involving
low emissivity coatings and gas fill is already
an acceptable solution when the window to
wall ratio is a reasonable percentage of the
whole; however, it is not acceptable to build
buildings with R-2 exteriors that are all glass!
Nevertheless, we are dealing with a moving
target—with improved thermal insulation
in walls, today’s windows will again have a
larger impact, but the continuing progress in
window technology ensures that there will
be viable solutions for the future. Research
currently is addressing further reductions in
heat transfer through glazing systems, low
conductance spacers, and insulated frame
systems and better methods for installing
windows in walls.
Facade performance needs
Conventional means of energy reduction include modest sized windows
with double glazing, spectrally selective glass, manually operated interior
shading, and dimming lighting controls.
Daylighting control systems must be
integrated with the building enclosure,
electric lighting, and HVAC controls.
These integrated façade solutions have
several functions—spectral control of
transmitted radiation to reduce cooling
loads and dynamic control of intensity
and direction of solar radiation to further improve visual comfort and capture
daylight savings. These control systems
must consider comfort and satisfaction
of occupants as these issues are related
to human performance in the work environment. The economics of building
occupancy indicates that the cost of
maintenance, taxes, and energy is about
3 percent and rent is about 10 percent;
the remaining 87 percent is the cost
related to occupant salaries or productivity. The issues involved here are that
advanced façades with lighting controls
and smart shading devices that can provide control of glare, thermal comfort,
and excellent energy efficiency.
Optimizing the design of such systems can be challenging. The designer
needs a range of building design tools
that must:
Summer/Fall 2008 33
• Allow integration strategies to be
explored.
• Allow facade performance to be
optimized.
• Make lighting tradeoffs between HVAC
and the façade.
• Explore commissioning and operational
issues.
To this end, the designer has available a series of tools for characterizing
and optimizing the properties of window
systems that include the Window 5 software suite which includes IGDB (spectral glass data sources), OPTICS (window glass) and THERM (window frame),
CGDB (complex glazing data base),
and WINDOW (whole window). Other
building design simulation tools include
ENERGY PLUS and RADIANCE, COMFEN (whole building commercial), and
RESFEN (whole building residential).
ENERGY SAVINGS THROUGH
REHABILITATION OF EXISTING
BUILDINGS AND IN THE DESIGN
OF NEW BUILDINGS
In this section, we highlight potential energy savings in the rehabilitation of
34 Journal of Building Enclosure Design
existing buildings and key elements in the
design process of new buildings.
Energy saving opportunities in
existing buildings
The rehabilitation process can be started
with lighting. Energy use for lighting averages
12 percent of the total in residential occupancies and 28 percent in commercial buildings.
Given the relatively small cost of fixtures, this
may be the first item on the retrofit list. The
next priority is the control of air flows. This
will require that air barrier systems be installed in all new and existing buildings. There
are many possible solutions such as:
1. An inexpensive but temporary solution that involves sealing all penetrations for AC, pipes, and ducts and
placing two or three coats of lime-cement stucco or other trowel grade air
barrier material on all leaky masonry
block surfaces.
2. A more costly but more effective solution involves adding continuous exterior
insulation integrated with an air barrier
and possibly also improved windows.
The design community has learned from
past weatherization programs that single
actions (e.g., adding attic insulation, replacing windows, or even sealing of some holes
in the building enclosure), while important,
do not have a high impact and can lead to
other problems if not holistically considered. The logical conclusion is that both a
holistic approach and professional insight
are necessary for these programs to be effective. The effective existing and emerging
housing retrofit programs involve inspections by independent experts to assess the
condition of a building, its equipment, and
its airtightness. On that basis, a range of
improvements of increasing complexity and
cost are suggested that, if employed in part
or fully, can be eligible for cost rebates to
help offset the cost of the inspection/analysis and part of the cost of implementing the
recommendations. Programs of this nature
are proving to be effective because the advice provided is informed and the costs are
partially recovered.
Energy saving opportunities during
design of new buildings
The key message of this white paper is
that every building is a system of interconnected assemblies and components and,
thus, every change in aspect will affect other aspects of building performance as well.
How does one evaluate the effect of those
changes? Marshall McLuhan was quoted as
saying: “Our Age of Anxiety is in great part
the result of trying to do today’s job with
yesterday tools.”
Architects and designers often do not
have adequate tools for evaluating longterm performance of buildings. There nevertheless is one powerful tool that makes
up for the lack of many artificial tools—the
collective brain of a design team. We need
to use it from the beginning to the end of
the construction process. We postulate
that a conceptual design should include:
1. A plan for design review that includes
trouble shooting by experts in heat,
air, and moisture control of buildings.
2. The inclusion of key elements in
mock-up lab and field testing.
3. Design intent for all systems included
in the commissioning plan.
Mock-up testing and commissioning are
likely to be done by an external agency.
The proposal from such an agency or testing lab defining all details of the proposed
work should be reviewed by the full design
team before it is approved.
Particular attention should be placed
on commissioning during the construction
phase. To better understand the benefits
of the commissioning process, please consult one of the many recent publications
on this topic (e.g., NIBS Guideline 3-2006,
Exterior Enclosure Technical Requirements for the Commissioning Process).
Experience indicates that the building enclosure specialist (a nonstructural,
technical professional whose job it is to
work with different teams to find missing enclosure interface detail drawings,
specify additional tests on test assemblies, etc.) who was employed by some
architecture firms in the 1970s brought
the expertise that we are now highlighting to these firms. Whether this function
is internal or external is a moot point; we
stress only the need for including such
expertise during both the design and construction processes.
CONCLUSIONS
The construction industry must build
on the strength of existing knowledge of
building science. Building enclosures—
their energy efficiency, durability and
the indoor environment—are today at a
cross-roads. On one hand, a large amount
of knowledge and expertise is available;
on the other hand, old approaches are
not as valid as they once were. It is time
to create a new vision because the stakes
are high. We need this new vision to improve our energy efficiency, maintain energy security, and sustain the economy.
Savings can be put back to more productive uses even though it will take time to
realize full return on investment. Yet, this
vision cannot be achieved without a mobilization and education of our society.
Unless major public/private initiatives are
developed, the strategy based on retrofitting existing buildings will not work.
As was the case during World War II, we
need society’s bond to win a 21st Century
war—but this one is to save the planet.
We support launching and sustaining
large-scale, long-term national programs
that blend policy, economics, and technology in public/private partnerships. We support making energy performance visible by
displaying performance, using devices that
monitor energy use from buildings to grid.
We support extensive participation of the
media in unleashing public imagination in
the support of different programs. Effectively, our proposal can be summarized as:
Think big, start small, and act now with the
focus on how.
ACKNOWLEDGEMENTS
This white paper was written by BETEC
Board members Drs. Mark Bomberg and
Donald Onysko based on plenary presentations by Drs. Stephen Selkowitz, Joseph
Lstiburek, and John Straube and other papers presented at the BEST 1 conference in
June 2008. Comments generated in discussions with numerous reviewers also have
been incorporated. The BETEC Board also
gratefully acknowledges discussions with Dr.
Selkowitz and the kindness of the Department of Energy’s Lawrence Berkley National
Laboratory that allowed reproduction of the
illustrations used in this paper.
This white paper was approved by the
BETEC Board for publication on August 25,
2008.
Comments or questions should be directed to BETEC Chairman Wagdy Anis, FAIA:
wanis@wje.com.
Summer/Fall 2008 35
36 Journal of Building Enclosure Design
Summer/Fall 2008 37
38 Journal of Building Enclosure Design
Feature
Field Monitoring of the
Hygrothermal Performance of
a New Class of EIFS Walls
By Achilles Karagiozis and John Edgar
Abstract
The development of new construction materials can be an expensive and risky proposition. This is particularly true if the material
is to be used as a barrier to air movement and bulk water entry
into the building envelope. How does a manufacturer ensure that
a material will work in all climates without risking deterioration of
the wall? Building test facilities in each climate zone and monitoring them over a multi-year period is not practical and would, in
any case, only confirm performance during those years. A more
economical and thorough approach is required to evaluate performance in a wide range of climates for an extended time period.
Research on walls with various cladding materials is being
conducted at the Natural Exposure Test (NET) Facility located in
Hollywood, SC. ORNL is monitoring the performance of fifteen
panels of EIFS, stucco, brick and other materials. The results of
continuous hourly monitoring are being compiled for subsequent
comparison with the results of computer simulations.
A vast amount of hygrothermal performance data has been
generated. This paper is the first in a series and will concentrate
on the description of the research program that was undertaken,
and to show some limited field data gathered during the first year.
Experimental results for two panels, one having a brick veneer
cladding and one having an EIFS, were selected for illustration as
they represent a typical range of performance data that has been
obtained for further hygrothermal analysis.
Introduction
Prior to 1996, Exterior Insulation and Finish Systems (EIFS)
had become popular as an exterior building envelope cladding
system in the residential and commercial construction market in
North America [1]. Since 1996, the commercial construction sector has continued to experience rapid growth; however, residential construction dropped as the EIFS cladding system, as being
built at the time, became associated with certain water intrusion
problems. Nissen [10] presented a summary of serious moisture
problems in barrier EIFS-clad walls in New Hanover County, including the city of Wilmington, NC.
Moisture problems ranging from high moisture content in the
exterior sheathing to wood rot in some houses were observed.
Many of the 3200 EIFS-clad homes in that area needed some remedial repair. Most of the water intrusion issues were traced to
flashing details and the penetration of water into the wall systems
at window joints [6, 8]. The installation of code mandated sub-sill
window flashing was not practiced by builders nor was diverter
flashing used at roof/wall intersections. Investigations showed
that approximately 45 percent of the damage occurred below the
corners of windows and 35 percent below missing roof flashing.
Problems of water intrusion were not unique to EIFS but the adverse publicity was focused on the system. The issue of water
penetration was limited to interface locations, not within the field
of the wall. Typically, small amounts of penetrating water could
dry through the wall assembly but problems developed if there
chronic wetting and moisture did not dry out quickly enough [8].
Questions were also raised about the effect of interior vapor
control strategy. At the time, an interior vapor barrier was mandated by code. Another major finding was that the windows installed in
these homes were not appropriate for the climate zone. These two
reasons, in combination with the flashing issues, were the prime
reasons for the failed performance observed in Wilmington, NC.
Although the problems with water intrusion appeared to be universal with all cladding materials, only EIFS was studied quantitatively.
Information on other claddings in NC is mostly anecdotal.
During this time period (1996 to 2001), a large number of
papers appeared that sometimes added more confusion to the
general literature. Many of the articles published were primarily
generated by opinions and not basic building science. Early versions of MOIST (M1), MATCH (M2) and WUFI (W) were valuable
in studies of moisture transport but were lacking material property data, surface transport coefficients, conservation of mass and
energy, and ability to account for wind-driven rain (M1 & M2) and
water penetration.
A number of scientific breakthroughs in the understanding of
the transport of heat, air and moisture through a building enclosure
became available from the International Energy Agency Annex 24
on Heat, Air and Moisture Transfer through New and Retrofitted
Envelope Parts. Simpler versions of these models, such as WUFI,
have now (since 2001) become available to the general public. The
hygrothermal tools and data that would have assisted the analysis of
moisture-induced failures were not available prior to 2001.
Of course, it is not possible to predict system behaviour of
improperly constructed wall systems even at this time simply because of the lack of detailed knowledge about specific faults.
In 2003, the Department of Energy (DOE) requested that Oak
Ridge National Laboratory address the performance issues associated with exterior foam insulation.
The perception of problems related to the use of exterior foam
insulation (EIFS) led to a substantial reduction in construction built
using EIFS.
Summer/Fall 2008 39
This reduced the potential energy savings in new
and renovation residential construction.
To meet the Zero Energy Building (ZEB) objectives laid out by the DOE Building America program, one cost effective option was to use EIFS wall
systems. A strategic research plan was developed
and proposed to EIFS Industry Members Association (EIMA) to partner with ORNL to investigate
the performance of EIF wall systems. At the same
time, ORNL would integrate some newer concepts
arising from their previous research on moistureengineered EIFS walls. These innovations included,
water drained systems using a fluid-applied water
resistive barrier, and EIF systems designed with
vented or ventilated drainage cavities.
The research project was conducted in two
phases. Below is a brief description of each phase
of the research project.
RESEARCH STEPS
A number of steps are involved in the research
for Phase I and II. Figure 1 provides an overview
of the main tasks that are required to achieve productive end results.
Figure 1. Research Approach for the EIMA/DOE/ORNL Project.
Phase I of the research program
Phase I, a 15-month field research project initiated in January 2005, was conducted to characterize the moisture and
• To validate the moisture and thermal performance of
thermal performance of various configurations of exterior cladding
a new class of EIF wall systems.
systems (EIFS, brick, stucco, concrete block, and cementitious fiber
• To quantify the performance of new EIFS and other wall
board siding).
systems that employ other types of exterior cladding.
The primary goals of the Phase I study were:
• To develop high quality data to calibrate a hygrothermal (moisture and temperature) computer model
with the unique features of EIFS to permit applying
the model to all climatic regions.
The hygrothermal research investigation included the
impact of innovative EIFS features, specifically the application of fluid-applied moisture control membranes, smart
vapor retarder systems (bi-directional membranes), and
the impact of exterior cladding venting, as well as the
overall thermal and moisture performance of EIFS.
Phase 1 study approach: In keeping with the DOE’s directive of promoting a whole-building approach to building design, operation and maintenance, the research project considered the building envelope in its entirety, rather
than studying isolated materials or component systems.
The research approach is summarized below:
• Characterize the moisture and thermal performance
properties of critical construction materials and subsystems used in exterior wall systems.
• Conduct field testing on a variety of exterior wall
systems to determine their thermal and moisture
response to the local weather condition over the
course of 15 months.
Develop performance information useful to the design
methodology that will permit architects and engineers to
optimize energy efficiency.
Figure 2. Natural Exposure Test (NET) Facility in Hollywood, SC.
To achieve these goals, a special building was designed
40 Journal of Building Enclosure Design
and constructed at Hollywood, SC, a Zone 3, mixed climate location, on near the Atlantic coast, south of Charleston Figure 2.
A flexible design was implemented to allow the change of
wall panels with ease, to compartmentalize the building into two
zones, and to allow control of the interior conditions. In Phase
I, a total number of 15 wall assemblies were integrated into one
side of the building (south-eastern exposure). In this way, all of
the assemblies would be exposed to similar weather conditions.
Building orientation and placement of the exterior walltest panels
were determined after careful consideration of historical weather
patterns in that location, including the prevailing direction of
wind driven rain.
The primary focus of this project was on the wall assemblies
that employed various EIFS configurations, particularly EIFS
with drainage systems. Table 1 lists the configurations for the
15 wall panels. Other cladding assemblies were also included
to provide additional information for validating the computer
model that represented widely different characteristics. These
were selected based on the construction typical to the region.
As noted previously, other cladding assemblies, existing and
yet to be developed, will be able to be studied using computer
modeling when verified by this kind of research.
Each of the wall panels contained a variety of sensors that
recorded temperature, relative humidity, and moisture content.
Table 1. Configuration of the Exterior Wall Assemblies Investigated During Phase I.
Panel / System
EPS
Attachment
Panel 1 EIFS
1 ½”
Flat
Ribbon &
Dab
Panel 2 EIFS
Panel 3 EIFS
Panel 4 EIFS
Panel 5 EIFS
Panel 6 EIFS
Panel 7 EIFS
CMU
Vapor Barrier
Note 1
Plywood
2 x 4@16”
Liquid
Plywood
2 x 4@16”
1 ½”
Flat
Notched
Trowel
Vertical
Ribbons
Vertical
Ribbons
Liquid
Plywood
2 x 4@16”
Vertical
Ribbons
Liquid
Plywood
2 x 4@16”
Vertical
Ribbons
Liquid
Plywood
None
Grooved
EPS
Plywood
Grooved
EPS
House
wrap
18 ga @16” R-11
Unfaced
Plywood
2 x 4@16”
Mat
House
wrap
House
wrap
OSB
2 x 4@16”
R-11
Unfaced
6 mil
Poly
R-11
Unfaced
None
1 ½”
Flat
4”
Flat
1 ½”
Flat
1 ½”
Panel 10 EIFS
Ventilated
1 ½”
Flat
1 ½”
Flat
Notched
Trowel
Notched
Trowel
Mech.
Fastened
Mech.
Fastened
Mech.
Fastened
Adhesive
Notched
Trowel
None
R-11
Unfaced
Yes
R-11
Unfaced
Mem-brane
Cavity
empty
None
R-11
Unfaced
None
R-11
Unfaced
None
Lath
Liquid
Plywood
2 x 4@16”
Notched
Trowel
Vertical
Ribbons
Liquid
18 ga @16” R-11
Unfaced
None
3.4 Metal
Lath
2-Layers Grade
D 60 Minute
ASTM
C1177
Gyp. Board
OSB
2 x 4@16”
R-11
Unfaced
None
1-Layers Grade
D 60 Minute
(behind foam)
OSB
2 x 4@16
R-11
Unfaced
None
OSB
2 x 4@16”
None
1-Layers Grade
D 60 Minute
OSB
2 x 4@16”
R-11
Unfaced
1 Coat PCP 1”flat Paint – later Woven Wire
Plaster Base
date
1 x 20 ga.
Note 2
None Brick ties
1”
flat
2 x 4@16”
R-11
Unfaced
Adhesive
3 Coat PCP None Mech.
Fastened
Note 2
Panel 15 Cementitious
Fiberboard Siding
None
Insulation
Liquid
1 ½”
Flat
Panel 14
Brick
None
Framing
Vertical
Ribbons
Panel 9 EIFS
Panel 13
(Stucco)
Sheathing
Notched
Trowel
1 ½”
Panel 12
(Stucco)
Weather
Barrier
1 ½”
Flat
Panel 8 EIFS
Panel 11 EIFS
Commercial
Drainage /
Air Space
Mech.
Fastened
Air Cavity 1” 1-Layers Grade
D 60 Minute
None
Typical Interior Finishing – ½” drywall, primed and painted (1 coat acrylic paint).
Note 1 – Finished with furred (1x2 treated lumber) ½” drywall, primed and painted (1 coat acrylic paint).
Note 2 - Painted white initially, plywood = ½”, OSB = ½”, lath = G 60.
R-11
Unfaced
None
Summer/Fall 2008 41
Figure 4. Relative Humidity Instrumentation Layout for EIFS Panel 5 and Brick Panel 14.
Figure 3. Field Testing Wall Dimensions for All Cladding Systems.
Hygrothermal issues still not fully understood or quantified.
Some panels included heat flux sensors. All sensors collected data on an hourly basis and transmitted it to the ORNL
Building Thermal Envelope Systems & Materials Energy Division
Research facility in Oak Ridge, TN for analysis.
A total of 15 months of data were collected from January 1,
42 Journal of Building Enclosure Design
2005 through March 30, 2006. The panel test area arrangement
is shown in Figure 3.
The research investigated the hygric performances of each
wall assembly. The field data and the hygrothermal model derived
from it are particularly useful not only in developing guidelines for
the use of EIFS but also in demonstrating the moisture and temperature control performance of EIFS as compared with other
types of exterior claddings.
Ultimately, the validation of computer modeling would extend
the value of the data to all cladding assemblies.
At this time, data is lacking on several aspects of the hygrothermal
performance of many wall systems, including EIFS. This is true for
several climatic effects, such as rainwater penetration, solar radiation,
night sky radiation, and the influence of wind speed and site/wall orientation on both the convective and mass transfer coefficients. The
response of various wall assemblies to exterior and interior hygric
loading is complex and represents a large effort to undertake properly. The findings of Phase I (not reported here) go some way towards
providing the necessary data. Earlier, some claims have been made
that adding exterior insulation (EPS) reduces the drying performance
of wall systems. For the Charleston region, the claim was not found
to be supported. Other claims have yet to be tested. Phase II affords
an opportunity to address some of these questions.
Phase II of the research program
Although the scope of the project was limited to fifteen panels,
the second phase of the project took a more complete approach
to gathering as much data as possible with specific attention to the
following issues.
Newer exterior-cavity vented EIFS had been shown, in Phase
I, to enhance the performance of conventional EIFS walls; still
not investigated, however, is whether there is a degradation
of their thermal performance as a result of air exchange in the
drainage space. Scientific and code committees have posited
that by introducing a vented air cavity between the insulation
and water resistive barrier the effectiveness of the exterior insulation might be negated to some degree by cold air entering
the drainage cavity. In Phase II, heat flux sensors for both the
south-east and north-west orientations were added to measure the thermal consequences of cavity ventilation.
The question of hygrothermal performance in EIFS walls due to
the effects of orientation (for example, a wall facing north vs. one
facing south) has also been raised. This issue was found to be critical
for the performance of stucco walls, where it directly affects both
hygric loading and the accompanying drying potential.
The orientation question becomes more complicated for both
stucco and brick when coupled with the effects of absorptive
cladding and solar driven moisture. It was not understood if the
same factors would affect a low mass, relatively non-absorptive
cladding like EIFS. Phase II afforded an opportunity to research
and quantify this effect for EIFS.
Table 2. Configuration of the Exterior Wall Assemblies Investigated During Phase II.
Panel / Orientation / Heat
Flux Sensor (HFS )/
System
EPS
Attachment
Drainage /
Air Space
Weather
Barrier
Sheathing
Framing
Insulation
Vapor
Barrier
Liquid
Plywood
Plywood
R-11
Unfaced
None
Liquid
2x
4@16”
Liquid
Plywood
Panel 1
Not used for the EIMA – ORNL Research
Panel 2, SE, EIFS
1 ½”
Flat
Panel 3, SE With Flaw,
HFS EIFS
Panel 4, SE EIFS
1 ½”
Flat
1 ½”
Flat
Notched
Trowel
Notched
Trowel
Notched
Trowel
Vertical
Ribbons
Vertical
Ribbons
Vertical
Ribbons
2x
4@16”
2x
4@16”
R-11
Unfaced
R-11
Unfaced
None
6-mil Poly
Panel 5, SE, HFS EIFS
4”
Flat
Notched
Trowel
Vertical
Ribbons
Liquid
Plywood
2x
4@16”
Panel 6, SE, HFS EIFS
1 ½”
Flat
Notched
Trowel
Vertical
Ribbons
Liquid
Plywood
Liquid
Plywood
18ga@16” R-11
Unfaced
Mat
OSB
Liquid
Plywood
2x
4@16”
R-11
Unfaced
None
2 Layers
Grade D 60
Minute
OSB
2x
4@16”
R-11
Unfaced
None
Panel 7, SE With Flaw,
HFS EIFS
Panel 9, SE, HFS EIFS
Panel 10, SE
Ventilated, HFS
1 ½”
1 ½”
Flat
Notched
Trowel
Mech.
Fastened
Vertical
Ribbons
Mech.
Fastened
Adhesive
Panel 11
1 ½”
Flat
Metal Lath
Not used for the EIMA – ORNL Research
Panel 12, 3 Coat Portland
Cement Plaster (Stucco)
SE, HFS
None
Mech.
Fastened
Note 2
3.4 Metal
Lath
2x
4@16”
2x
4@16”
None in stud None
cavity
R-11
Unfaced
R-11
Unfaced
None
6-mil Poly
None
Panel 13
Not used for the EIMA – ORNL Research
None
Brick ties
Air Cavity
1”
1 Layer
Grade D 60
Minute
OSB
2x
4@16”
R-11
Unfaced
None
Panel 15, SE, HFS Brick
None
Brick ties
Air Cavity
1”
OSB
2x
4@16”
R-11
Unfaced
None
Panel 16, NW EIFS
1 ½”
Flat
Notched
Trowel
Vertical
Ribbons
1 Layer
Grade D 60
Minute
Liquid
Plywood
Liquid
Plywood
2x
4@16”
R-11
Unfaced
Panel 18, NW, With Flaw,
HFS EIFS
1 ½”
Flat
Notched
Trowel
Vertical
Ribbons
Liquid
Plywood
2x
4@16”
R-11
Unfaced
None
Panels 19 to 25
Not used for the EIMA – ORNL Research
Panel 26, NW, Ventilated,
HFS EIFS
1 ½”
Flat
Plywood
2x
4@16”
R-11
Unfaced
None
Panel 14, SE, HFS Brick
With Flaw
Panel 17, NW, HFS EIFS
1 ½”
Flat
Notched
Trowel
Adhesive
Vertical
Ribbons
Metal Lath
Liquid
2x
4@16”
R-11
Unfaced
None
Typical Interior Finishing – ½” drywall, primed and painted (1 coat acrylic paint)
Note 1 – Finished with furred ½” drywall, primed and painted (1 coat acrylic paint)
Note 2 – Painted white initially, Plywood = ½”, OSB = ½”. Lath = G 60
Summer/Fall 2008 43
Another unknown was the impact of incidental
water penetrating the exterior EIFS lamina, the first
line of defense. Currently, some literature suggests
that even if very small amounts of water are allowed
to pass through the exterior foam, catastrophic failure
may occur. The proposed ASHRAE SPC 160P modeling standard recommends that 1 percent of water that
impacts the wall surface be injected onto the exterior
surface of the water-resistive barrier to simulate a
leak. A systematic moisture engineering research effort is being implemented in Phase II to provide data to
address performance of wall systems associated with
water penetration.
Finally, but not least, a limited hygrothermal property database exists for EIFS materials. This hampers
designers, who cannot conduct an analysis of the performance of EIFS in different climates with sufficient
accuracy. In Phase II, an extensive testing program is
being carried out to obtain data on the moisture performance of various materials used in Phase I and II of
this research study.
Phase II study approach: Phase II used the same research approach and protocol as Phase I. The Phase II
research approach is summarized below.
• Continue the development of accurate hygrothermal property characterizations of the critical construction materials.
• Conduct field testing to expose a series of innovative
Figure 5. Monthly Average Relative Humidity Distribution in EIFS Wall.
Figure 6. Monthly Average Relative Humidity Distribution in Brick Wall System.
44 Journal of Building Enclosure Design
wall systems (trowel applied water-resistive barriers) to real
environmental conditions.
• Conduct field testing to expose a series of innovative wall
systems with additional water penetration loading by directing water into the wall.
• Develop performance information to be used in the formulation of design guidelines, which will provide options for
energy efficiency, while addressing heat, air and moisture
transport (Phase I and II).
Phase II includes both newly constructed wall panels and
some original 20 month old Phase I panels. The total number of
panels remained at fifteen. The description of each panel monitored in Phase II is provided in Table 2.
The emphasis of DOE and ORNL participation throughout Phase II has been on the development of quality temporal
(time-dependent) data for the calibration of the ORNL hygrothermal models.
Instrumentation layout
The same number of sensors was used for each wall system
in both Phase I and Phase II, with the exception of the heat flux
sensors (used only in Phase II) that were added to a number of
panels.
In each of the Phase II panels, the wall system included 17
thermistors, 6 relative humidity sensors, and 8 moisture content sensors. In Figure 4 the sensors locations are noted for
two different wall assemblies.
The same sensor arrangement is found in all three types of
Figure 7. Cooling period positive heat fluxes into interior space weather station.
wall assemblies, the only difference being in the positioning of the
RH sensors in the brick and EIFS cladding see Figure 4.
The sensors in the stucco panels were positioned in the same
way as in the brick panel.
Hygrothermal results
This paper provides some results for two panels—an EIFS and
a brick assembly, evaluated during Phase I of the study. It is beyond
the scope of this paper to present all the findings for even a single
wall; a comprehensive report of the study will be published.
The relative humidity was measured in six locations in each of the two walls. The results are shown in
Figures 6 and 7. The averaged monthly relative humidities are
plotted for each wall. Results are plotted for all six sensors for a
period of 1.4 years, starting in January 1 2005.
Sensors RH_1 and RH_2 are located in the exterior cladding,
RH_3 is located in the exterior side of the sheathing board, while
sensors RH_4 and RH_5 are located on the interior side of the
sheathing board, top and bottom, and the last sensor, RH_6 is located at the outer face of the gypsum board. For the EIFS wall,
RH_1 is located in the exterior EIFS lamina, while RH_2 is located
at the interface between the inner face of the foam and the vaporpermeable, trowel applied weather resistive barrier. For the brick
wall, sensor RH_1 is imbedded in the mortar joint half thickness of
the brick, while RH_2 is located on the building paper.
In Figure 5, a clear yearly cycle is exhibited, showing the decoupling of the thermal and moisture performance due to the
presence of the exterior foam insulation.
The sensors bounding the exterior sheathing board show very
low relative humidities that have not exceeded 68 percent at any
period of the year RH_1 and RH_2 show close agreement with
the exterior environment, with a condensation period present in
RH_2 during late August and the beginning of September.
However, as this occurs in the vicinity of the air gap close to
the interior side of the foam, no damage is expected to occur.
In Figure 6, the inner portions of the wall system (i.e. the
wood framing and sheathing) are coupled to the brick exterior.
As expected, very high relative humidities were found in sensor
RH_3 (imbedded in the exterior sheathing board). For at least
7 months of the year, the average monthly relative humidity at
that sensor exceeded 80 percent. According to the proposed
ASHRAE 160P such hygric conditions can cause mold damage to a
material. Indeed, even on the interior side of the sheathing board,
the readings for one month (December) showed average monthly
relative humidity exceeding 80 percent. It is evident that this brick
wall arrangement is not performing satisfactorily for the climatic
conditions present in the Charleston region.
The cooling heat fluxes into the interior of the building
are shown for Wall 5 (EIFS) and Wall 14 (brick) in Figure 8.
The average cooling season values are plotted for each wall. A
heat flux sensor was located at the exterior side of the gypsum board. The measured heat fluxes from the brick wall are
approximately 2.6 times higher than those measured in Wall
5. This represents a substantial savings in energy required to
cool the space insulated with exterior foam vs. fibreglass batts
in the wall cavity. To a lesser yearly degree the opposite effect
occurred during the winter months. The brick stored energy
and conducted it inwards reducing the heating load. It should
be pointed out that the EIFS wall has a higher nominal R-value
and that better performance should be expected. It is interesting however, that the ratio of the R-values is approximately 1.4
times.A dedicated weather station was deployed at the NET Facility where the exterior temperature, relative humidity, wind
speed and orientation, solar insulation normal to wall, horizontal
rainfall, and wind-driven rain were continuously monitored.
Summer/Fall 2008 45
Conclusion
This is the first study that has monitored the heat and
moisture performance of a wide range of EIFS wall systems. The test program described provides the scope of
the effort expended thus far. The detailed findings will be
published in due course and will illustrate how well the performance can be modeled. The inclusion of several other different cladding systems allows the side by side performance
comparison for the specific climate of the test facility.
This side by side wall heat and moisture performance provides a sound foundation for generating quantitative building science knowledge. An enormous amount of information has been
generated that will become available for hygrothermal modeling
validation analysis. It is planned that after the MOISTURE-EXPERT model has been validated, additional analysis will provide
performance assessment of these wall systems for other locations
in the USA.
Many different systems were monitored during the 2.5-year
period of the DOE/ORNL/EIMA study. While not reported here,
the drained EIFS walls were found to perform as well as or better than other cladding systems during all parts of the year.
The field analysis performed in the Charleston region has the
potential to provide wall performance answers to a number of issues of interest in hot and humid climates. In Phase III, we expect
to extend this investigation to a number of other regions of the
USA, using advanced hygrothermal modeling. Achilles Karagiozis,
PhD., is a distinguished research and development staff member of the Oak Ridge National Laboratory, in Oak Ridge, TN.
John Edgar is a Technical Manager, Building Science at Sto Corp., in
Atlanta, GA. The authors of this paper would like to extend sincere
thank to Mr. Stephan Klamke, EIMA Director, Bill Preston from
Dryvit Inc, and Andre Desjarlais, Phil Childs and Jerry Atchely from
the Oak Ridge National Laboratory, and Florian Antretter from the
Fraunhofer Institute in Building Physics. Finally with out the financial
support from the Department of Energy (Program Manager: Marc
LaFrance) this project would not have been possible.
REFERENCES
[1] Thomas R.G. Jr., “Exterior Insulation and Finish System Design
Handbook”, 1992, pp.230.
[2] William, M.F. and Williams, B.L., “EIFS Resistance to Moisture: Facesealed Barrier Performance”, Development, Use and Performance
of Exterior Insulation and Finish Systems (EIFS), ASTM STP 1187,
Mark F. Williams and Richard G. Lampo, Eds., American Society for
Testing and Materials, Philadelphia, 1995.
[3]Lampo, R.G. and Trovillion, J.C., “Performance of Class PB and Class
PM Exterior Insulation and Finish Systems Under Impact Loadings”,
Development Use and Performance of Exterior Insulation and Finish
Systems, ASTM STP 1187, Mark F. Williams and Richard G. Lampo,
Eds., American Society for Testing and Materials, Philadelphia, 1995.
[4] Piper, R.S. and Raab S., “Factors Affecting the Water Resistance of EIFS
Base Coats and Insulation Board”, ASTM International Symposium on
Exterior Inuslation and Finish Systems (EIFS): Performance of EIFS
Worldwide, September 21-24, 1992 Arlington VA.
[5] Bomberg, M., Lstiburek J., and Nabhan F., “Performance Evaluation
of Exterior Insulation and Finish Systems (EIFS)”, Seventh Conference on Building and Science and Technology, March 20-21, 1997,
pp.1-15.
[6] Brown, W., Ullett, J. Karagiozis A. and Tonyan T., “Barrier EIFS Clad
Walls: Results from a Moisture Engineering Study” , J. Thermal Insul.
and Bldg. Envs., Vol. 20, Jan., 1997, pp. 1-21.
[7] Crandell. J.C. and T. Kenny., “Investigation of Moisture Damage in
Single-Family Detached Houses Sided with Exterior Insulation Finnish Systems in Wilmington NC, NAHB Research Center, Inc., 1995,
August.
[8] Nelson, P. and Waltz M. EIS - Surface Sealed Wall Systems that Need
Flashings, Exterior Insulation Finish Systems (EIFS): Materials, Properties, and Performance, ASTM STP 1269, 1996, pp. 149-164.
[9] Kudder J. R. and Lies K.M., “Comparison of Class PB EIFS Lamina
Water Transmission Test Methods”, Exterior Insulation Finish Systems (EIFS): Materials, Properties, and Performance, ASTM STP
1269, 1996 pp. 84-102.
[10] Nissen, N. J.D., “Severe Rotting Found in Homes with Exterior Insulation
Systems”, Energy Design Update, Vol. 15, No. 12, Dec, 1995, pp.1-3.
[11] N issen, N. J.D., “Ordinary Paint as Replacement for Poly Vapor Retarder”, Energy Design Update, May, 1994, pp.5-7.
[12]Hutcheon, N.B., “Humidified Buildings Canadian Building Digest”,
UDC 697.93, Division of Building Research, National Research
Council Canada 1963.
[13] Salonvaara M.H. and Karagiozis A.N., “EIFS Hygrothermal Performance Due to Initial Construction Moisture as a Function of Air
Leakage, Interior Cavity Insulation and Climate Conditions”, Thermal Performance of Exterior Envelopes of Buildings VII, Clearwater, FL, 1998, pp. 179-188.
[14]Karagiozis A.N., “Applied Moisture Engineering”, Thermal Performance of Exterior Envelopes of Buildings VII, Clearwater, FL,
1998, pp. 239-251.
[15]Karagiozis, A.N. and Kumaran, M.K., “Computer Model Calculation on the Performance of Vapor retarders in Canadian Residential Buildings”, ASHRAE Transactions, Vol. 99(2), 1993, pp.
991-1003.
[16]Kunzel, H.M., Humidity controlled vapor retarder reduce risk of moisture damage, Proceedings of the 4th Symposium, Building Physics in
the Nordic Countries, Espoo, Finland, Sept. 9-10, 1996, pp.447-454.
[17] National Building Code of Canada. 1990. Location of vapor barriers, 9.25.6.2. p 292.
[18]Ojanen T. and Kumaran M. K., “Effect of Exfiltration on the Hygrothermal Behavior of a Residential Wall Assembly”,J. Thermal Insul.
And Bldg. Envs, Vol. 19, 1996, pp.215-227.
[19]Karagiozis, A., Künzel, H.M., Holm A.: WUFI-ORNL/IBP - A North
American Hygrothermal Model. Contribution to “Performance of
Exterior Envelopes of Whole Buildings VIII”, Dec. 2-7 2001, Clearwater Beach, Florida.
[20]Karagiozis, A. and Hadjisophocleous G. “Wind-Driven Rain on
High-Rise Buildings”, Thermal Performance of Exterior Envelopes
of Buildings VI, Clearwater Beach, Florida, 4-8 Dec. 1995.
[21]Hens, H. and Janssens A., “Inquiry on HAMCAT CODES”, International Energy Agency, Heat, Air and Moisture Transfer in Insulated
Envelope Parts, Report Annex 24, Task 1, Modelling, 1993.
[22] Building Science Forum, “Exterior Walls: Understanding the Problems”, National Research Council Canada,1983.
46 Journal of Building Enclosure Design
Feature
Detection of Moisture and Water Intrusion
Within Building Envelopes By Means of
Infrared Thermographic Inspections
By Antonio Colantonio, Public Works and Government Services Canada
ABSTRACT
Infrared thermographic imagers have been used in the building industry since the 1980s, mainly for building envelope and heat
loss analysis. Infrared imagers have developed significantly over the
past 15 years and are now vital tools to determine performance
characteristics of walls and roofs for both energy and structural
integrity. With interior health issues coming to the forefront—such
as mold issues—the infrared imager has again become a vital diagnostic tool.
Although infrared imagers do not detect presence of mold, they
can be used to detect presence of moisture by means of variances
in heat transfer brought on by conductance of water and phase
change heat loss or gain. The infrared camera can be readily utilized
to detect the extent of moisture intrusion in building structures
in a much faster and convenient way than conventional moisture
detection devices. When commissioning new building envelopes,
or carrying out building condition inspections of existing building
envelopes, it is imperative to differentiate the source of the moisture accumulation between interior or exterior sources since the
recommendation for remedial action may a considerably.
Moisture detection methodologies for interior and exterior
inspections vary and equipment specifications are different for
both types of inspections. The physical mechanisms that produce
moisture patterning in infrared wavelengths are different for both
interior and exterior inspections. Ensuring optimal inspection conditions is paramount in order to obtain accurate inspection results.
This paper discusses the various types of thermal patterns created
by surface penetration of water versus those patterns created by
air leakage from the building interior in cold winter conditions.
Moisture detection methodologies for interior inspections are discussed and the importance of timing is stressed regarding detection
of moisture within assemblies by non-destructive means.
INTRODUCTION
Exterior wall assemblies used in medium and high rise buildings
can be classified into four generic types of wall types: 1) masonry, 2)
architectural pre-cast, 3) metal and glass curtain wall, 4) insulated
steel assemblies. For low rise and residential buildings there is an additional type of generic wall assembly: 5) wood and steel frame.
Within these generic types of assemblies there is considerable variation in the type of cladding, insulation and assembly configuration of
components required for control of moisture and air migration. Much of
the variation is dependent on architectural aesthetics but these all need
to address environmental factors imposed by local weather conditions
throughout the year. In both extremely cold and hot humid climates, the
control of water and water vapor through the building envelope is critical to the durability and long-term performance of enclosure assemblies.
Vapor retarders are used to control vapor diffusion.
Air barriers, either as single components or as a group of components are used to control air movement from the exterior through to
the interior. Air movement can transport 10 to 100 times more moisture through unintentional openings in the air barrier assemblies than
vapor diffusion through the leakiest vapor barrier or retarder. Detection of openings that facilitate moisture migration is critical to the control of vapor flow and moisture accumulation in exterior assemblies.
Figure 1. Moisture within insulation under one ply sheet membrane roof assembly as seen
from exterior.
Figure 2. Moisture within insulation seen from the interior of a building. Figures courtesy of
Paul Frisk, FLIR Systems Canada.
TYPES OF WALL ASSEMBLIES
Exterior wall assemblies can be designed as either a) face seal or
b) cavity wall. Within face seal assemblies there are both low mass
or high mass type walls. Low mass walls consist of generally insulated stud walls (either load or non load-bearing) with solar, wind,
rain and vapor controlling exterior cladding. High mass walls consist
of solid masonry walls (either insulated or uninsulated). These high
mass walls can either be load-bearing or enclose an integral steel or
concrete structural frame.
Summer/Fall 2008 47
Face seal assemblies rely on one plane (either interior or exterior
surfaces) for the purpose of stopping water, vapor and air migration
into and though the wall. If and when there are breaches in these air
and water vapor impermeable surfaces, the degree to which water
can be evacuated is dependent on the drainage planes and permeability of the materials within the wall assembly and the cladding.
Cavity wall assemblies are more varied. They include traditional
non-ventilated masonry wall assemblies as well as modern rain screen
and pressure equalized rain screen type wall designs. These latter exterior enclosures come in numerous forms of generic wall types as
mentioned earlier. Cavity walls rely on the exterior cladding to provide
the water penetration protection along with through wall flashings to
drain potential moisture to the exterior. These types of walls may or
may not have a separate vapor barrier material for control of vapor
diffusion. These types of walls rely on a series of materials to provide
an air tightness or air barrier plane. In cold climates, air barrier materials are located either on the interior side of the wall or the interior
side of the insulation within the wall. The air barrier assembly is hidden
from view when located within the wall making inspection and repair
difficult after construction. (In warm climates, the air vapor barrier assembly is generally placed on the exterior side of the insulation layer.)
The cladding materials in rain screen and pressure equalized rain
screen assemblies are designed to vent and drain excess water that
has penetrated the cladding materials. The air space between the
cladding and the insulation or air barrier assembly is used as a capillary break between the cladding and the back up wall.
When breaches in the air barrier assembly occur in cavity walls,
ventilation/weep holes in the cladding provide an easy route for migration of air through to the exterior or from the exterior into the
building interior. There is no certainty that cladding vent holes will
be close to the breach in the air barrier assembly. Variability of location and size of air barrier openings result in variable air flow patterns within and through the wall assembly. In extremely cold or hot
humid climates, airflow transports moisture from either the interior
or exterior into the wall assembly. This is a primary cause for mold
formation and premature wall deterioration.
The use of infrared thermography for detection of openings in
air barrier assemblies can be carried out by means of pressurization
or depressurization of building interiors prior to and during infrared
thermographic inspections. A resultant by-product of this type of inspection methodology is the accumulation of moisture within the
wall assemblies as a result of increased pressurization.
Thermal patterns generated by building pressurization produce
48 Journal of Building Enclosure Design
information on the location and possible severity of the air barrier opening but in many situations, are accompanied by residual moisture accumulation in various building materials adjacent to air barrier breaches.
TYPES OF ROOF ASSEMBLIES
Sloped roof assemblies
Roofs can be classified into sloped and low sloped assemblies.
Sloped assemblies are generally associates with residential buildings
with vented attics. Air leakage is detectable in sloped roof assemblies at soffit joints or around roof projections provided that there is
a temperature differential between interior and exterior of at least
10ºF (5ºC) and a pressure differential of at least 5 Pa.
Infrared imagers cannot be used to determine presence of moisture within these assemblies from exterior inspections. The resultant
effect of roof leaks in sloped roofs is best detected by interior inspections on insulated ceiling assemblies saturated with rain or melt
water. Since moisture is detected by means of conductive heat loss
variances (the result of differences in the thermal conductance of the
dry roof material and the moisture laden materials), these patterns
are most obvious when temperature differentials between interior
and exterior are greater than 18ºF (10ºC). Alternatively, if moisture
finds its way into the interior gypsum board or plaster, evaporative
cooling may be detected during the drying out stage of the roof leak.
This option only exists when there has been wetting and drying is
occurring within absorptive materials.
Low-sloped roof assemblies
Low-sloped roofs can be classified into conventional and inverted
roof membrane assemblies. Conventional assemblies are where the
roof membrane is located on the exterior of the assembly. Inverted
roof assemblies place the roof membrane underneath the insulation.
The roof insulation in inverted assemblies is generally non-water
permeable and retains much of it insulation properties during wet
conditions. Even though we could see moisture within surface materials of inverted roof assemblies, there is no way to detect possible
roof membrane defects since these are hidden from view and the
presence of ponding water within the insulation or ballast materials
does not relate to membrane failures. Infrared thermography can
only be used to detect moisture within absorptive insulation underneath roof membranes in conventional type assemblies.
Within conventional roof assemblies there are built-up roofs (BUR)
and single ply membrane assemblies. BUR’s consist of either three- or
four-ply asphalt impregnated felts or two-ply modified bitumen roof
membranes. Single-ply membrane assemblies are made up of three
types of membranes (thermosets, thermoplastics and modified bitumens) that are either mechanically fastened to the roof substrate or
ballasted. Infrared thermography can be used to detect the presence
of moisture within the insulation layer found underneath the roof
membrane in these roofs. Two types of methodologies are used; a)
transient method using solar heat gain during day time and inspecting
transient conditions during and immediately after dusk, b) static method employed four to eight hours after sunset when heat flow is near
steady state conditions and surface temperatures variances between
dry and wet insulation is a function of primarily conductive heat loss.
The first is exclusively carried out from the exterior while the second
type can be carried out both from the exterior or the interior.
The static method requires a minimum of 18ºF (10ºC)
temperature differential if the inspection is carried out from the exterior. The roof membrane is required to be dry and free of snow
cover so as to ensure full inspection coverage. Exterior inspections
with outside ambient temperatures lower than 41ºF (5ºC) produce
variable results and are not recommended. If inspections are carried
out from the interior, the temperature of the rain water should be at
least 10ºF (5ºC) cooler than interior ambient.
The transient methodology is primarily used in the industry due
to its greater effectiveness. The degree of success is affected by such
variables as the thickness of ballast, the reflectivity of the roof membrane or ballast, the temperature differential between interior and
exterior, wind speed during exterior inspection, the absorptiveness
of the insulation with the roof assembly, and the amount of solar heat
gain throughout the day of inspection. All these factors play a role
in the detection of moisture within roof insulation and determination of the specific locations of membrane failure a tricky activity.
Inspections with wind condition greater than 10 kph produce variable results and are not recommended. Under ideal conditions, the
window of opportunity to detect moisture within the roof assembly
is generally about two to three hours after sunset. Unfavorable site
conditions reduce this time frame or eliminate it completely.
If suitable environmental factors are not present and standard
inspection methodologies are not adhered to, false negative results
will be achieved.
Temperature resolution is not a critical technical requirement for
the transient methodology since the temperature variance between
dry and wet insulation is generally in the 4ºF to 7ºF (2ºC to 4ºC)
range. In the static methodology, temperature variance between dry
and wet insulation is generally in the 0.4ºF to 2ºF (0.2ºC to 1ºC)
range for surface temperatures. Most low-cost thermal imagers today come with this level of temperature resolution and are acceptable
for use in both methodologies. Better temperature resolution allows
for better detection of possible moisture in unfavorable conditions.
The difficulty of analysis of data from unfavorable inspection conditions is that many other non consequential thermal signatures also
become apparent and need to be evaluated and discounted. These
types of thermal signatures include uneven ballast, heavy flood coats,
reflective roof surfaces, multiple roof felt layers and membranes, reflected energies from adjacent protrusions and wall surfaces, variable
emissivity conditions due to dirt built up.
Detection of moisture within built-up roofs can be carried out by
either walking over the roof assembly, surveying from higher adjacent roofs, or by fixed wing airplanes or helicopters. All are acceptable methodologies when suitable inspection conditions are present
and appropriate infrared imagers are used. Small roofs may be easier
and more cost-effective to inspect by simple walk though using inexpensive 10K to 20K pixel imagers. Large roofs with vantage points
from other adjacent roofs make hand-held inspections cost effective
if employing 80K pixel imagers with better spatial resolution capabilities. For very large low-sloped roofs, or for many roofs in one
geographical location or campus, aerial inspection is the quickest and
most efficient means of collecting data on BUR moisture intrusion.
Dedicated high spatial resolution imagers (300K pixel or higher)
are required to obtain suitable spot size resolution to define moisture
patterning and roof features. Focus and high speed vibration are issues
that need to be addressed in data collection from aerial fixed-wing or
helicopter inspections for both fixed mounted and handheld imagers.
EXTERIOR INSPECTIONS
Moisture patterning as a result of rain water
In cold climates, commissioning building envelope inspections are
not always carried out in sub-zero temperatures. Exterior ambient
temperatures between 34°F and 50°F (1°C and 10°C) are conditions
often experienced by thermographers testing buildings for air leakage faults. During these conditions, rainfall may occur prior to actual
inspections. The type of rainfall and intensity, along with wind conditions often result in variable wetting patterns on building claddings.
Both type of cladding, and assembly, influences the variability of
wetting patterns on walls. Non-porous cladding materials shed water and do not retain rainwater thus do not show variable effects of
rainwater on their surface temperatures after a rainfall. Porous materials show greater variable temperature effects as a result of moisture accumulation. Lightweight porous materials (wood and stucco)
again show greater thermal variances due to rainwater penetration
than high mass type porous material such as stone.
Rainwater patterns generally affect cladding materials thus thermal patterns are a result of the reduced thermal resistance of the
cladding materials. In cold climates the most significant durability issue is the potential for freeze/thaw damage to the cladding materials
at areas where saturation occurs. In locations where rainwater penetration gets through the cladding, other materials such as weather
barriers and sheathing often protect entry into the insulation layers
and structure. In some conditions, where penetration does occur
into these materials, infrared thermography is able to locate these
problem areas when temperature gradients greater than 18°F (10°C)
exist through the building exterior envelope.
Figure 3. Neutral Building Pressure (0 Pa), To = -8ºC, No precipitation or snowfall for at
least 7 days prior to inspection. Arrows point to suspected moisture accumulation within the
limestone cladding due to rain and melt water throughout winter.
Summer/Fall 2008 49
Rainwater penetration patterns are generally associated with
the top section of walls and most likely around parapet walls. Most
buildings only experience rainwater penetration at top floors unless
located in areas with a high driving rain index, or during hurricanes
or tornados. Other areas where rainwater penetration may occur
are at sloped or protruding walls or drainage planes from upper wall
sections. Windowsills and parapets are examples of such drainage
features. Sloped relief details in stone masonry walls are another example of such conditions Figure 3.
Moisture patterning as a result of melt water
In winter months, solar gain and thaw conditions result in melt
water runoff from roofs, sloped projections and other architectural
features. In these situations, masonry and other porous cladding materials are affected by the accumulation of surface moisture. These
patterns are visible through infrared thermography as a result of
conductive heat flow and are more pronounced as the temperature
differential between interior and exterior increases.
Melt water patterns are affected by solar heat gain and often dry
out on the surface but interstitial moisture remains throughout the
winter months. Moisture accumulation due to melt water may often
not be visible due to surface drying aided by solar heat gain but subsurface cladding moisture is detectable through the use of infrared thermography. The significance of this moisture is that it can result in increased freeze/thaw potential of the mortar holding masonry together
and in some situations results in premature rusting of metal reinforcing
and ties within the masonry. Sloped areas on stone and masonry walls
are areas that attract melt water throughout the winter months. Often
these areas are also characterized by staining and dirt build-up created
by the surface water accumulation and adhesion.
Moisture patterning as a result of ground water
Solid masonry walls with stone foundations without ground protection are susceptible to ground water absorption. Ground water
wicks its way up the wall at the ground floor of the building through
capillarity. Reduced thermal resistance values occur at the stone walls
immediately above the ground during the heating season. This moisture may result in mortar deterioration throughout the wall thickness and be susceptible to freeze thaw on the outer sections. Infrared inspection of these walls can detect moisture accumulation by
means of increased conductivity and surface temperatures. Thermal
patterns are not mottled as in other types of assemblies but rather
consistently warmer throughout the lower sections of the first floor
adjacent to the grade around the building.
In general, surface temperature variations between the first floor
walls and the rest of the building can only be discerned at exterior ambient temperatures below 23°F to -4°F (-5°C to -20°C). Inspections
carried out during higher temperatures require more sensitive infrared
equipment to discern surface temperature variations due to ground water absorption. This type of thermal pattern is not always apparent since
it is rather homogeneous in nature rather than mottled and variable.
AIR LEAKAGE TESTING AND RESULTANT MOISTURE
PATTERNING
Negative building pressures and ambient temperatures
Figures 5 and 6 demonstrate the amount of moisture accumulation that can occur within masonry cladding as a result of stack effect
brought on by low winter exterior ambient temperatures. Both images taken during negative building pressures are void of air exfiltration patterns but Figure 5, taken at a lower ambient temperature
12°F (-11°C), displays greater amount of moisture accumulation
within the masonry cladding at the top of the building than Figure 5
taken at temperatures approximately 18°F (10°C) higher.
The only other variable in this image is significantly increased
negative pressure in the higher temperature situation that could
have resulted in slightly modifying existing moisture patterns. The
increased negative pressure combined with the time prior to inspections that this condition existed may have reduced the amount of
moisture within the wall cladding. In addition, due to reduced exterior ambient temperatures, stack effect would have been reduced for
the period prior to capture of image in Figure 5, thus reducing the
amount of moisture especially at the top of the building envelope.
Positive building pressures and ambient temperatures
The thermal images in Figures 7 and 8 demonstrate the amount
of moisture accumulation that can occur within masonry cladding as
a result of stack effect brought on by reduced exterior ambient temperatures. Both images, taken during positive building pressures, display thermal patterns created by air exfiltration patterns in addition
to previously accumulated moisture patterns due to stack pressures.
These air leakage patterns overpower the moisture induced thermal
patterns in both exterior ambient temperature conditions.
The image taken at the lower ambient temperature illustrates
greater amount of moisture accumulation within the masonry cladding
than the image taken at temperatures of approximately 10°C higher.
This is consistent with the thermal patterns produced during the negative building pressure inspections. The only other variable in this image is slightly increased positive pressure in the higher temperature
situation that could have resulted in the slight
modification of existing moisture patterns.
Figure 4. Ground floor of solid masonry wall assembly illustrates warmer surface temperatures due to
rising damp from ground water in foundation wall.
50 Journal of Building Enclosure Design
Moisture patterns resulting from direct
and diffuse leakage
The thermal images seen in Figures 9 to
12 demonstrate the variances between moisture patterns created by both direct and diffuse air leakage. These images also illustrate
the variations during both positive and negative
pressure conditions during inspections.
Moisture patterning is most visible during
negative building pressure inspections since air
leakage patterns do not overpower those created by moisture within
the cladding or insulation. If conducting inspections within an hour or
so after initializing negative building pressure, then moisture patterning
created by normal operating conditions become most visible in the infrared. Moisture patterning appears to be more apparent in areas where
diffuse air leakage occurs through the exterior walls, rather than at areas
where direct air leakage occurs during these inspections.
One possible explanation for this phenomenon is that in diffuse air
leakage conditions, moisture has a greater potential to get trapped
into porous materials rather than in situations where direct air leakage occurs from the interior to the exterior. What has been generally
observed is that moisture accumulation around areas of direct airflow
paths occur at the peripheral areas of the openings and not immediately at their locations. Again heat and air flow from the exfiltrating
air generally will not allow for moisture retention at the immediate
opening but rather some distance around the openings where there
Figure 5. Negative Building Pressure (-140 Pa), To = 0ºC. Figure 6. Negative
Building Pressure (-8 Pa), To = -11ºC.
Figure 7. Positive Building Pressure (+40 Pa), To = 0ºC. Figure 8. Positive
Building Pressure (+25 Pa), To = -11ºC.
is less air flow to move the moisture further out of the cladding materials. In very cold conditions (-22°F/-30°C and lower), visual signs of
hoar frosting is visible at these problem areas. Pre-existing moisture
patterning does not seem to be affected to any degree during positive
pressure inspections other than to make them less apparent due to
the much warmer surface temperatures created by the exfiltrating air
at openings within the air barrier assembly. Positive building pressure
inspections will result in additional moisture deposition within the wall
assembly and thus create additional areas of moisture accumulation
within the wall area that may not be present during normal operating
conditions of the building. Both significant pressure (between 50 to
150 Pa) and considerable duration (greater than four hours of positive
pressure) are required before additional moisture patterning is visible
due to positive building pressure conditions in building with average to
above average leaky air barrier assemblies.
When looking at buildings during cold weather conditions, variations in the thermal signatures created by naturally occurring conditions will take considerable time to be modified and in some conditions, may not be modified at all. In Figures 9 to 12 the masonry
areas around the vent located in the central section of the third floor
appears warm in the negative pressure inspections, even through
negative pressures were imposed for more than 2 hours prior to
each inspection. Exterior ambient temperature seems to have little
effect on the dissipation of stored heat and moisture within the masonry around these locations. In these conditions, greater time is
required under negative building pressure to eliminate the stored
heat from air leakage within the masonry cladding.
Duration of high building pressure and moisture
accumulation.
The thermal images in Figures 13 and 14 were taken on subsequent mornings. Figure 14 illustrates positive pressure imagery produced 24 hours prior to the negative pressure imagery in Figure 13.
The arrows at the parapet walls of this 24-story building identify the
moisture accumulation within the brick cladding as a direct result of
positive building pressure imposed on the building for test purposes.
The moisture patterns were not present prior to the positive building pressure being induced into the building and did not appear until
after four hours of positive building pressure.
Figure 13 illustrates the thermal imagery from the same area of
this building while being subjected to negative building pressure the
following evening. Note that the thermal patterns due to air leakage
are absent from this image as are the patterns created by the moisture accumulation within the brick cladding at the upper sections of
the elevation from earlier in the day. The thermal bridging patterns
are still evident. This image indicates that moisture accumulation, as
with heat build-up due to excessive air leakage, given a full 24-hour
time period, will dissipate when the driving force of the heat and
moisture accumulation within the cladding is not present.
As seen in Figure 14, leakage areas were random in various section of the building and were not wide spread, but the sustained abnormal positive building pressure during testing did result in additional
moisture migration from the building into the masonry cladding. This
is a common occurrence in both solid as well as cavity wall assemblies.
In cavity wall assemblies, moisture migration often travels from the
source of the air barrier opening up to the top sections of the wall cavity due to convection cycles and thus moisture patterns appear more
Summer/Fall 2008 51
pronounced at the top section of wall cavities and building elevations.
Another factor that contributes to the increased build-up of moisture
accumulation at top sections of buildings is the increased stack effect
pressures generally found at these elevations during winter months.
MOISTURE PATTERNING AND PHASE CHANGE
Exterior inspections (freeze thaw cycles)
Phase change of moisture within porous cladding materials from
a liquid to a solid occurs at temperatures slightly below freezing.
Phase change from a solid to a liquid occurs when temperatures
increase above freezing. In the phase change from a solid to a liquid, an endothermic reaction, melting ice within the wall is visible
through reduced surface temperatures. Phase change from a liquid
to a solid is an exothermic reaction and is visible through increased
surface temperatures. These phenomenon occur independent of either positive or negative pressures. The accompanying thermal images in Figures 15 to 16 illustrate the endothermic effects of melting
ice within the building cladding.
Figure 9. Negative Building Pressure (-140 Pa), To = 0ºC. Figure 10. Positive
Building Pressure (+40 Pa), To = -0ºC.
Figure 11. Negative Building Pressure (-140 Pa), To = -11º. Figure 12.
Positive Building Pressure (+40 Pa), To = -11ºC.
Figure 13. Negative Building Pressure (-60 Pa), To = -7ºC, maintained for a
duration of 4 hours prior to inspection.
Figure 14. Positive Building Pressure (80 Pa), To = -7ºC, maintained for a
duration of 5 hours prior to inspection.
52 Journal of Building Enclosure Design
The dark areas on the fourth floor masonry cladding illustrate
the distinctive endothermic pattern generated by the phase change
of melting ice within the masonry. It appears reasonably consistent
during both the negative and positive inspections during the same
evening. The cold areas above the window heads on the third and
fourth floor windows are typical of air leakage into the building during negative building pressure conditions.
The moisture patterning in the wall due to accumulated moisture
over the winter months appears warm around the floor slabs and is
present during both the negative and positive pressure inspections.
During the positive building inspection, these moisture patterns appear to be overpowered by the thermal patterns created by the
air leakage through the walls from the building interior. Both images were taken during same evening, four hours between the two
settings. Due to the lower exterior ambient temperatures, phase
change phenomenon is not visible at low outside temperatures.
Moisture accumulation is visible during both inspections, but more
during positive building pressure inspections than slightly negative
pressure inspections.
Interior inspections (evaporative cooling)
Phase change of moisture from a solid to a liquid and from a liquid
to a gas requires energy. This is considered an endothermic reaction.
The energy for these phase changes is absorbed from the building
materials holding this moisture. It takes five times more energy for
water to change to vapor than for ice to change to water.
Thus, evaporation of moisture within surface materials results
in a considerably greater cooling of surfaces than solid ice melting to
a liquid. This is one of the principle reasons that detection of moisture through evaporative cooling is easier to spot than melting of
moisture within porous claddings. The amount of surface cooling is
directly proportional to the rate of evaporation and the amount of
moisture within the assembly. These factors are temperature dependent (both interior and exterior temperatures), vapor pressure
dependent and time dependent.
Phase changes going from a gas to a liquid or from a liquid to a
solid are considered exothermic reactions in that they release energy to the adjacent building materials which hold moisture. Therefore condensation of water vapor or freezing of water within porous
building materials produce warmer surface patterns. Condensation
will generate a greater thermal signature that freezing of water within porous materials. In winter inspections, it is possible to generate
both heat signatures due to condensation of interior warm moist air
and cooling patterns due to ice melting within porous cladding.
Thermal patterns due to evaporative cooling from interior inspections vary according to the cause of the moisture accumulation
within the wall, ceiling or floor assembly. The sources of moisture
include but are not limited to: a) rain and/or melt water intrusion,
b) condensation due to air leakage, c) water from plumbing and
sprinkler systems, d) occupant activities (kitchens, washrooms, wet
preparation areas, slop sinks), e) cleaning activities within buildings,
f) fire and flood damage and, g) building materials drying out during
construction stages (concrete, drywall, masonry). The duration of
wetness along with appropriate temperatures results in either material damage or more problematic, development of mold.
Evaporative drying of interstitial moisture within exterior wall assemblies can occur either to the interior or exterior or combinations
of both depending on the environmental conditions at the time of inspection and the vapor transmissivity of materials on either side of the
embedded moisture. Evaporative drying to the exterior is generally
very difficult to see from interior inspections but not impossible. The
easiest moisture to detect occurs from evaporative drying of interior
surface materials. The presence of moisture within exterior wall assemblies during cold winter months will result in colder interior surface temperatures of exterior walls than the temperatures created
by evaporative cooling on interior surfaces. During warm summer
months, intensity of evaporative cooling thermal patterns may be reduced due to conductive through-wall heat gain. Moisture detection
Figure 15. Negative Building Pressure (-140 Pa), To = 0ºC. Figure 16.
Positive Building Pressure (+40 Pa), To = 0ºC. Both images taken during
same evening, four-hour time span between the two images.
on interior partitions, floors and ceilings is generally easy to detect due
to more static base surface temperatures resulting from stable interior
ambient conditions. Variable exterior ambient conditions do not interfere with evaporative cooling thermal patterns on interior surfaces.
The insurance industry uses infrared thermography to determine
when walls are completely dry after floods. Visual inspections cannot
always be relied on and moisture meters do not provide a complete
picture of potential wet areas. The use of infrared thermography
allows for non destructive evaluation of the potential causes and
sources of the moisture. The tool is generally used in combination
with moisture meters to validate acceptable amounts of moisture at
a specific location.
The issue of limit state moisture detection (with all environmental
factors being equal) is subject to both spatial and thermal resolutions
of infrared equipment used. Shorter distances to target surfaces address spatial resolution limitations of infrared equipment. Thermal
resolution limitations of equipment cannot be compensated for during inspection methodologies for moisture detection. Most medium
to low cost imagers provide at least 100 mK thermal resolution. This is
generally good enough to see signs of evaporative cooling during initial
wetting and drying phase. When trying to determine complete dryness,
imagers with considerably better thermal resolution (30 to 50 mK)
provide much better limit state information. For this reason, it is
recommended that interior moisture detection be carried out with
imagers with at least 50 mK thermal resolution.
SUMMARY
Moisture within low-sloped roof assemblies is detectable by transient or near steady state heat flow methodologies. The window of
opportunity for transient condition testing is two hours after sunset
following a sunny day. Near steady state condition testing can be carried out from both the interior and exterior providing that there is a
sufficient temperature differential to produce a thermal signature and
surfaces are unobstructed and easily viewable. Aerial infrared inspections are recommended for large or multiple roofs areas or locations,
but walk-on inspections are cost effective for small roof inspections.
Spatial resolution becomes an issue when large distances to target object surfaces are encountered. Thermal resolution is less of an issue
since moisture effects for transient testing generally produce temperature differences between the 4ºF to 7°F (2°C to 4°C) range.
Moisture patterning due to rainwater and melt water penetration
of the building cladding is visible if the cladding is porous and absorbs
moisture and there is a thermal gradient through the wall to distinguish
dry from wet cladding. This is generally a transient condition and requires inspection after sunset to carry out comparative analysis of patterns from all elevations of the building. Rainwater generally is detected
at upper sections of buildings most susceptible to penetration due to
wind forces. Melt water patterns are visible at projections and interior
corners where ice and snow build up occur in winter months.
Moisture patterning due to ground water absorption in solid
masonry buildings generally display as homogeneous higher surface
temperatures at the base of the building just above grade. It requires
a thermal gradient through the building enclosure of at least 50°F
(30°C) to be visible.
Moisture patterns within masonry cladding created by air leakage
from interior sources due to stack effect are most prominent at upper
sections of building during sub-zero winter months.
Summer/Fall 2008 53
These patterns are more visible in negative building pressure
conditions rather than positive building pressure conditions provided that negative building pressure test conditions do not exist for greater than a 24-hour time period. In conditions where
normally occurring exfiltration results in localized increased cladding temperatures and resultant moisture accumulation, a time
duration of greater than 24-hours would be needed to eliminate
the effect of that normal heat loss pattern. Thus most negative
building pressure exterior building inspections often still see
these thermal patterns in conjunction with their resultant moisture accumulation.
When conducting exterior large building infrared thermographic inspections during cold winter months, it is advised to
conduct the negative building pressure inspection prior to the
positive building inspection if both are planned for one evening’s
work. If the work is spread out over a number of days, then either
inspection can be carried out first since the resultant moisture
accumulation from internal sources will be allowed to dissipate
due to solar gain and natural diffusion of moisture to outdoors
through the cladding material.
Phase change of moisture (freeze/thaw cycles) within porous
cladding materials is visible only during exterior ambient temperature conditions between 32°F and 23°F (0°C and -5°C) when
moisture within the cladding is most susceptible to phase change.
Positive and negative building pressure conditions do not affect
the formation and detection of moisture within the process of
phase change. The thermal pattern will show up as either much
colder or much warmer than adjacent surface areas depending if
moisture is freezing to a solid state or thawing to a liquid state.
Moisture is detectable during interior inspections by means of
evaporative cooling. The amount of surface cooling is directly proportional to the rate of evaporation and the amount of moisture
within the assembly. These factors are temperature dependent
(both interior and exterior temperatures), vapor pressure dependent and time dependent. Non-vapor transmissive coatings will
affect the rate of drying and thus the intensity of the thermal signature. Imagers with better thermal resolution (50 mK or better) are
recommended for this type of moisture detection work.
REFERENCES
Colantonio, Antonio and Desroches, Garry: “Thermal patterns on solid masonry and cavity walls as a result of positive and
negative building pressures”, pp 176 – 187; Proc. Thermosense
XXVII; SPIE Vol. 5782, March 2005.
ACKNOWLEDGEMENTS
The author wishes to thank the Panel for Energy Research
and Development (PERD) for their continued funding of field research in the detection of moisture within masonry structures
and infrared thermography commissioning methodologies leading
to reduction of energy utilization within buildings. He also wishes
to acknowledge the assistance of Garry Desroches from PWGSC,
Western Region for the capture and data processing of many of
the thermal images illustrated within the paper.
PORTLAND, OREGON
CALL
FOR
PAPERS
THEME: A new design paradigm
for energy efficient buildings
The energy economy of the globe is about
to be restructured in recognition of the unsustainability of the increasing demand for oil and the drive for replacement sources and
modes of energy supply. The building sector of the economy currently draws upon 40% of
total energy use and is responsible for almost half (48%) of all Green House Gas emissions
annually. This has come about from a time when energy costs were never expected to have
a lasting impact on the national economy. The new design paradigm will need to apply
all of the ingenuity that the design professions can muster to affect the demand side for
energy use in buildings. This must be done for both new buildings and the host of existing
buildings. It is not enough to only make more efficient use of energy; we must also improve
the durability of buildings and provide the air quality and livability that is required for a
healthy and productive population. The connectivity among the myriad of decisions that are
made by the developers, owners, design professionals, manufacturers and the trades has to
be recognized in order to achieve a successful end result.
This conference encourages all who are involved in the research, design and construction
of new buildings and the renovation of existing infrastructure to put forth their very best
efforts to achieve high performance buildings that significantly contribute to achieving the
restructuring needed.
CallforPapers7x4ad.indd 1
54 Journal of Building Enclosure Design
APRIL 12-14, 2010
The areas for consideration:
• Energy efficiency and durability
• Fenestration and lighting
• Moisture effects
• Control of indoor environment
• Innovative materials and systems
Important dates:
Deadline for abstracts: Jan 15, 2009
Abstract Notification: Feb 28, 2009
Papers Due:
Aug 15, 2009
LIST OF POSSIBLE TOPICS:
www.thebestconference.org
SUBMIT ABSTRACTS TO:
www.thebestconference.org/call
INFORMATION CONTACT:
Patricia Cichowski at NIBS
pcichowski@nibs.org
10/8/2008 11:29:47 AM
Feature
Use of PCM-Enhanced
Insulations in the
Building Envelope
By Jan Kosny, PhD and David W. Yarbrough, PhD, PE, Oak Ridge National Laboratory
ABSTRACT
A phase change material (PCM) alters
the heat flow across the building envelope
by absorbing and releasing heat in response
to cycling ambient temperatures. The benefit of a PCM is reduction in heating and
cooling loads and in many cases a shift in
peak-load demands and the time of day of
the peak load.
Ambient or interior temperature cycling past the phase change temperature
range is necessary for the PCM to function.
The design of a PCM application requires
selection of material, identification of PCM
location and bounding thermal resistances,
and specification of the amount of PCM to
be used. PCM can be distributed in an insulation or building material or packaged for
localized application. This paper describes
small-scale laboratory testing, large-scale
laboratory testing, and field studies undertaken to evaluate the energy savings potential for PCM in the building envelope.
INTRODUCTION
A PCM with a phase change temperature
near the temperature of the conditioned
space results in a small temperature difference between the PCM and the interior air
during the phase change. The heat flow in or
out of the conditioned space depends on the
thermal resistance between the PCM and the
interior air. A reduction in the temperature
difference translates to a reduction of heat
flow. Heat retained by the PCM is returned
to the ambient during the “discharge” part
of the diurnal cycle. This discharge is controlled by the thermal resistance between
the PCM and the inside air and the level of
thermal resistance between the PCM and
the outside. The design of a PCM application must address these factors.
Energy and thermal comfort benefits
of conventional massive walls, floors, or
slabs, have been well known for centuries.
PCM-enhanced building materials have
been utilized for at least 40 years as lightweight alternatives for conventional massive systems.
Many PCMs have been considered for
building applications, including inorganic
salt hydrates, organic fatty acids and eutectic mixtures, fatty alcohols, neopentyl
glycol, and paraffinic hydrocarbons. In the
US, there were several moderately successful attempts in the 1970s and 1980s to
use different types of organic and inorganic
PCMs to reduce peak loads and heating
and cooling energy consumption (Balcomb
1983). Previous investigations focused on
impregnating concrete, gypsum, or ceramic masonry with salt hydrates or paraffinic
hydrocarbons. Most of these studies found
that PCMs improved building energy performance by reducing peak-hour cooling
loads and by shifting peak-demand time.
In past studies, non-encapsulated paraffinic hydrocarbons generally performed
well (Tomlinson et al. 1992), but they sometimes compromised the fire resistance of
the building envelope. Kissock et al. (1998)
reported that wallboard including a paraffin
mixture made up mostly of n-octadecane,
which has a mean melting temperature of
75°F (24ºC) and a latent heat of fusion of
65 Btu/lb, “was easy to handle and did not
possess a waxy or slick surface. It scored
and fractured in a manner similar to regular wallboard. Its unpainted color changed
from white to gray. The drywall with PCM
required no special surface preparation
for painting.” In addition, Salyer and Sircar
(1989) reported that during tests of 4×8
ft sheets of wallboard with PCM, there
was insignificant loss of PCM after three
months of exposure to continuously cycled
100°F (38ºC) air.
The ability of PCMs to reduce peak
loads is also well documented. For example, Zhang, et al. (2005) found peak
cooling load reductions of 35 to 40 percent in side-by-side testing of conditioned
small houses with and without paraffinic
PCM inside the walls. Similarly, Kissock
et al. (1998) measured peak temperature
reductions of up to 50ºF (10°C) in sideby-side testing of unconditioned experimental houses with and without paraffinic
Figure 1. Small-scale test of a localized PCM showing heat flux (Btu/ft2·hr).
Summer/Fall 2008 55
PCM wallboard. Kosny (2006) reported
that PCM-enhanced cellulose insulation
can reduce wall-generated peak-hour
cooling loads by about 40 percent .
Small-scale laboratory
tests
The use of a heat-flow meter appartaus
to study transient heat flow has been discussed (Kosny et al. 2007) and (Alderman
2007). Both distributed and localized PCM
applications have been evaluated
by comparing insulation with PCM
and insulation without PCM subjected to the same thermal cycling.
Figure 1 is an example of transient heat
flux data that show the difference between an insulation containing a localized
PCM and the same insulation without
PCM. The area between the curves is a
measure of the reduction of heat flow to
the cold side of the test.
The overall saving requires an additional step of determining how much of the
heat contained in the PCM is returned to
the ambinet during the “discharge” part of
the cycle. The time required to “charge”
the PCM shown by the horizontal part of
the curve for the material with PCM is
controlled by the amount of PCM and the
level of thermal resistance between the
PCM and the elevated temperature. In
this example there was thermal resistance
of 9 ft2∙h∙°F/Btu (R 9) between the PCM
and the warm side of the test specimen
and 5 ft2∙h∙°F/Btu (R 5) between the PCM
and the cold side of the specimen.
The time scale starts with the specimen
at constant temperature and no heat flow
across the boundaries. Figure 2 summarizes data obtained with a heat-flow meter
and insulation containing distributed PCM.
The results in Figure 2 illustrates how the
performance depends on the amount of
PCM present. A 70 percent reduction in
cumulative heat flow is shown for the test
specimen with 30 wt. percent PCM. This
overall savings depends on the efficiency
with which the heat absorbed by the PCM
can be discharged to the ambient.
Large-scale laboratory testing of walls containing insulation with distributed pcm
During 2002-2004 PCM-enhanced
fiber insulations were tested for their
effectiveness as wall-cavity insulation.
56 Journal of Building Enclosure Design
Figure 2. Small-scale determination of the effect of increasing PCM loading.
Figure 3. Heat flux measured during a dynamic hot-box measurement in a 2x6 wood-frame wall containing PCM-enhanced cellulose insulation.
Small amounts of different cellulose–
PCM blends were made using a pilotscale production line (Kosny 2006). In
this project, microencapsulated paraffinic
PCM was used. The PCM microcapsules
were between 2 and 20 micrometers
in diameter with melting point 78.5°F
(25.8˚C). This PCM is produced with
the use of a microencapsulation technology that holds wax droplets inside hard
acrylic shells. Since production of cellulose
insulation includes the addition of dry chemicals, the addition of a dry PCM component
does not require significant changes in the
manufacturing or packaging processes.
A series of steady-state heat flow apparatus thermal conductivity measurements were conducted on the two- inch
thick samples of PCM-enhanced cellulose
insulation. These tests showed that the
addition of up to 30 percent of the microencapsulated PCM does not increase the
thermal conductivity of the cellulose insulation (Kosny 2006).
A nominal 8×8 ft wood-frame wall
specimen was used for transient hot-box
testing of a PCM–cellulose blend. The test
wall was constructed with 2×6 in. wood
framing installed 16-in. OC. Three wall
cavities were insulated with cellulose insulation with density 2.6 lb/ft3. Three remaining wall cavities were insulated with
a cellulose–PCM blend at a density of 2.6
lb/ft3 containing 22 wt percent PCM. It
is estimated that about 38 lb of PCM-enhanced cellulose insulation (containing 8 lb
of PCM) was used for this experiment.
At the beginning of the hot-box
measurement, temperatures on both
surfaces of the specimen were stabilized
at about 65°F (18.3˚C) on the cold side
and 72°F (22˚C) on the warm side. The
temperature of the warm side was rapidly
increased to 110°F (43.3˚C). After about
120 hours, the hot-box heaters were
turned down and the temperature of the
warm side of the wall was reduced by
natural cooling to 65°F (18.3˚C). Figure
3 shows the heat fluxes for both sides of
the wall recorded during the rapid warmup period.
It took 15 hours to charge the PCM
material in the wall. Heat fluxes on both
sides of the wall were measured and
compared. For three five-hour time intervals, heat fluxes were integrated for
each surface. Comparisons of measured
heat flow rates on the wall surface,
which was opposite the thermal excitation, enabled an estimate of the potential thermal load reduction generated by
the PCM. In reality, most daily thermal
excitations generated by solar irradiance
are no longer than five hours (peak-hour
time). Heat flux was measured during the
first five hours after the thermal ramp.
The PCM-enhanced cellulose material
reduced the total heat flow through the
wall by over 40 percent . The load reduction for the entire 15 hours of the PCM
charging time was close to 20 percent .
Surface temperatures on the PCM part of
the test wall specimen were approximately 2°F (16.6˚C) lower during the time of
the thermal ramp (cooling effect).
Field testing of insulation
with PCM
Two small-scale field tests were performed on 2×6 in. wood-frame walls
insulated with PCM-enhanced cellulose
Figure 4. Comparison of surface heat fluxes recorded during field experiment which took place during
a sunny week in April.
Summer/Fall 2008 57
insulation. Test walls were located in Oak
Ridge, TN and Charleston, SC. In both cases, PCM walls were located next to identical
wood-frame walls containing cellulose insulation with no PCM. To estimate the effect of direct solar radiation, the walls tested in Oak Ridge faced south and the walls
tested in Charleston faced northwest.
Figure 4 shows heat fluxes recorded
in Tennessee on test walls during a sunny
week in late April 2006. Exterior surface
temperatures on the Oak Ridge walls were
cycling between 120°F (48.8˚C) during the
days and 55°F (12.7˚C) during most nights.
Field test data demonstrated that the PCM
wall was more thermally stable than the
conventional wall. Significantly lower heat
fluxes were observed in the PCM wall:
peak-hour heat flux was reduced by at
least 30 percent compared with the conventional wall without PCM. In addition, a
shift of about two h in the peak-hour load
was observed in the PCM wall.
Analysis of the temperatures in the
tested walls showed that the PCM was
going through full charging and discharging
processes during the 24-h time period.
Recorded temperature profiles in
Figure 5 show that the PCM thermally
stabilized the core of the wall as a result
of its heat storage capacity. Temperature
peaks were notably shifted inside the
PCM wall. Significantly lower temperatures were observed during the night in
the wall cavities where no PCM was used.
The conventional wall (with no PCM)
was warming up and cooling down more
quickly than the wall with PCM.
Figure 5. Temperature profiles inside the wall cavities of the south-facing test walls (no-PCM wall located
on the east side, PCM wall located on the west side), during a sunny week in late April in Oak Ridge, TN.
Analysis of the PCM discharge
time: dynamic tests of the
residential attac containing
PCM-enhanced PCM
One of the most important design
criteria for building assemblies containing PCM is the charging and discharging
times, which has to be less than 24 hours.
If PCM is not fully discharged before the
start of the next cycle, then the full thermal storage potential will not be available.
In order to investigate the total chargingdischarging times for a full-scale attic assembly, dynamic hot-box experiments
were performed in the residential attic
module shown in Figure 6.
The attic module was tested under periodic temperature changes in the Large Scale
Climate Simulator (LSCS) at the Oak Ridge
National Laboratory. Two concentrations of
microencapsulated
PCM were tested
(5 percent and 20
percent by weight).
The main focus of
the attic tests was
discharging time of
the PCM, since dynamic hot-box testing of the wall had
already proved the
good thermal performance of the PCMenhanced cellulose
insulation. Charging
is not a problem in
attics because of the
intensive
fluctuaFigure 6. Test attic module used for testing of PCM-enhanced cellulose.
tions of the attic air
58 Journal of Building Enclosure Design
temperature during sunny days (a rapid increase in temperature caused by the sun).
However, the attic cooling process is significantly slower.
In a well-designed PCM application,
100 percent of the PCM material should
be able to fully discharge before the beginning of the next cycle.
During the dynamic lSCS tests, the
model of a residential attic was subjected
to periodic changes of temperature [65°F
(18.3ºC) for about 16 hours, rapid temperature ramp to 120ºF (48.8ºC) and
exposure to 120ºF (48.8ºC) for about 4
hours, followed by natural cooling back
to 65°F (18.3ºC)]. An array of thermocouples installed at one inch intervals was
used to monitor the temperature distribution across the attic insulation.
One of the interesting findings from
the analysis of temperature data was that
only layers of insulation located higher
than four inches from the bottom of the
attic were involved in the phase change
process. An analysis of the temperature
profiles demonstrated charging and discharging of the PCM (similar to those presented in Figure 3 for PCM wall) even in
attic insulation containing only five percent
PCM. It took about six to eight hours to
fully discharge the energy stored in these
layers. No forced ventilation was needed
to discharge the PCM.
CONCLUSION
Several applications of PCM-enhanced
building insulations have been tested and
analyzed over the past four years.
Two forms of PCM application were
considered: dispersed PCM in cellulose wall
insulation, and PCM application with fiberous insulations as a part of an attic insulation
system.
1.Laboratory-scale testing has demonstrated the potential for energy savings with
PCMs.
2. A dynamic hot-box test that included a
40°F (2.2˚C) thermal ramp, performed
on a 2×6 wood frame wall, demonstrated about 40 percent reduction of the
surface heat flow as a result of the use of
PCM. This finding was confirmed by the
field tests.
3. A dynamic hot-box test performed on
the attic containing PCM-enhanced cellulose insulation proved that PCM can be
fully discharged without the use of additional forced ventilation of the attic.
Jan Kosny is a research engineer in the
Building Technology Center at the Oak Ridge
National Laboratory. Dr. Kosny has been an
active researcher in the field of building science for 25 years. His areas of interest include materials, mathematical modeling, and
development of advanced building systems.
David Yarbrough is a member of the
research staff of the Building Technology
Center at the Oak Ridge National Laboratory and a Principal at R&D Services, Inc. Dr.
Yarbrough has been active in thermal insulation research for over 25 years.
References
Alderman, R. J. and D. W. Yarbrough
2008, “Use of Phase-Change Materials
to Enhance the Thremal Performance of
Building Insulations”, Thermal Conductivity 29 , John R. Koehig and Heng Ban,
Editors, DEStech Publications, Inc. pp
129-136.
Balcomb, J.D., R.W. Jones, C.E. Kosiewicz, G.S. Lazarus, R.D. McFarland, W.O.
Wray. 1983. Passive Solar Design Handbook. ISBN 0-89553-124-0. American
Solar Energy Society, Inc.
Kissock, J. Kelly, J. Michael Hannig,
Thomas I. 1998. “Testing and simulation
of phase change wallboard for thermal
storage in buildings.” Proceedings of 1998
International Solar Energy Conference, Albuquerque, June 14–17. J.M. Morehouse
and R.E.Hogan, Eds. ASME.
Kosny J., Yarbrough D., Wilkes K .,
Leuthold D., Syad A. 2006. “ PCM-Enhanced Cellulose Insulation – Thermal
Mass in Lightweight Natural Fibers” 2006
ECOSTOCK Conference, IEA, DOE,
Richard Stockton College of New Jersey,
June 2006.
Kosny J., D. W. Yarbrough, T. Petrie
and S.A. Mohiuddin 2008 “Performance
of Thermal Insulations Containing Microencapsulated Phase Change Material” pp
109-119.
Salyer, I., and A. Sircar. 1989. “Development of PCM wallboard for heating and
cooling of residential buildings.” Thermal
Energy Storage Research Activities Review.
U.S. Department of Energy, New Orleans,
March 15–17.
Tomlinson, J., C. Jotshi, and D. Goswami. 1992. “Solar thermal energy storage
in phase change materials.” Proceedings
of Solar ‘92: The American Solar Energy
Society Annual Conference, Cocoa Beach,
FL, June 15–18.
Zhang, Meng, M.A. Medina, and Jennifer
King. 2005. “Development of a thermally
enhanced frame wall with phase-change
materials for on-peak air conditioning demand reduction and energy savings in residential buildings.” International Journal of
Energy Research. 29(9):795–809.
Summer/Fall 2008 59
Feature
Real R-Value of Exterior
Insulated Wall Assemblies
By Mark Lawton, P.Eng., Patrick Roppel, P.Eng., David Fookes, P.Eng., Anik Teasdale St Hilaire, PhD., and
Daniel Schoonhoven
ABSTRACT
The recent drive towards sustainable
building construction has placed new emphasis on the provision of durable wall
assemblies that provide a high effective
resistance to heat flow (R-Value). The
authors’ practice focuses on large multiresidential, commercial and institutional
buildings constructed of concrete, steel,
masonry and glazing systems. In these
types of buildings, and particularly in the
temperate climate of British Columbia’s
Lower Mainland, thermal performance
has not historically been treated as a
high priority item. Now, however, the
requirements of sustainability programs
such as LEED are requiring architects to
design wall systems that provide high levels of thermal resistance. Architects are
often shocked at the difference between
effective R-value of a proposed opaque
wall assembly and the nominal R-value
of installed insulation materials. The difference is a result of the thermal bridges
associated with structural elements and
connections that pass through the building thermal envelope.
The authors have undertaken analyses, using the modeling program
THERM, to numerically evaluate the
effective thermal resistance of some
typical wall assemblies used in high-rise
residential buildings. We evaluated the
impact of slab edge detailing and a variety of secondary structural elements
needed to support the cladding. We
have developed a method of presenting
the information in a manner that architects can practically use to determine
actual insulation thicknesses required to
obtain the overall walls’ desired thermal
performance.
60 Journal of Building Enclosure Design
INTRODUCTION
A number of factors are causing architects to place more attention on the overall, effective thermal resistance of opaque
wall assemblies used in non-combustible
buildings. Clients are demanding that
more attention be paid to sustainability
and energy conservation either directly
by specification, or by participation in programs such as LEED. Energy conservation requirements are typically defined by
reference to standards such as ASHRAE
90.1 or Canada’s National Energy Code
for Buildings. These standards have both
prescriptive and performance based compliance paths. Both require knowledge of
the effective thermal resistance of opaque
enclosure assemblies.
A major challenge in non-combustible
buildings is that wall assemblies often have
highly conductive structural elements
passing through the thermal insulation so
that the overall or effective thermal resistance of opaque wall assemblies can be
much less than the nominal R-value of the
installed thermal insulation. With the complex, three-dimensional heat flow paths in
these “commercial” wall assemblies, calculating the effective thermal resistance is
a difficult process that requires tools such
as 2D or 3D heat flow computer simulation programs. Application of such tools
is beyond the capability of most architectural offices.
The challenge is such that in most jurisdictions where compliance with ASHRAE
90.1 is required by code, bylaw or specification, the impact of thermal bridges created by cladding attachment has historically been ignored. This is now changing.
The importance of thermal bridges related to cladding attachment in common wall
assembles is becoming increasingly recognized (Peer 2007), and there are even
initiatives to better define actual thermal
performance of wall assemblies by test.
The authors were directly confronted
with the issues on a major residential
project in Vancouver, Canada where they
acted as the building envelope professionals undertaking design and construction
review of the enclosure systems. The
project encompassed a total of 15 buildings; typically 5 to 13 storys designed by
six different architects. The development has high sustainability requirements
including compliance with LEED Gold.
Complicating matters was the fact that
the project has to be complete by an immovable date so that iterative design cycling had to be minimized.
The mechanical engineer for the project carried out initial energy use modeling and defined thermal performance requirements for the enclosure assemblies.
The provided requirements were:
Each of the architects turned to the authors firm to help them design wall systems
Roof
Walls
Shading
U value
R
W/m2/oC value coefficient
(BTU/ft2/
oF)
.238
(.0440)
.379
(.067)
15
0.47
(.0827)
12
Windows 2.335
(.411)
Floors
24
2.4
0.69
Table 1: Thermal Resistances assumed by
Modeling.
For further reading on thermal
bridging in relation to wall thermal
performance:
Study on heat transfer of light steelframed composite walls in cold areas.
Cui, Yong-Qi (School of Municipal and
Environmental Engineering, Harbin
Institute of Technology); Wang, ZhaoJun; Zhang, Su-Mei. Source: Journal of
Harbin Institute of Technology (New
Series), v 14, n SUPPL., January, 2007,
p 63-66
Thermal Insulation and Thermal
Bridge of Steel-Framed Walls. Suda,
Noriyuki (technical Development Bur);
Uno, Nobuyoshi; Shimizu, Jun; Kanno,
Ryoichi; Sugita, Koji. Source: Nippon
Steel Technical Report, n 79, Jan, 1999,
p 35-40
that met these performance requirements
in addition to all the other performance,
constructability and budget restraints imposed in the design process. Many of the
architects were surprised to learn that the
wall systems that they had used in previous high-rise residential construction fell
far short of the defined thermal resistance
requirement, primarily because of the influence of thermal bridges. They obviously
had questions about whether they could
simply modify the types of assemblies that
they had experience with by, for example,
adding insulation or whether that had to
make a dramatic departure from their initial design assumptions and if so, to what?
In an effort to assist architects, the authors undertook a program of modeling
typical systems with THERM and created
a method of transmitting results in a manner that aided the decision making process
of the architects.
TYPICAL WALL SYSTEMS
Most regions develop “locally typical”
methods of constructing high-rise residential buildings.
What is locally typical depends on climate, the cost and availability of components and assemblies and what the local
design and construction community is
comfortable with and finds cost effective.
In Vancouver, typical high-rise residential buildings can be said to have the following characteristics:
• They are concrete-framed.
• Exposed slab edges including projecting balconies and “eyebrows”
are common.
• They use a high percentage of
glazing, particularly to the “view”
directions of north (mountains) and
west (ocean).
• Glazing is often “window-wall”, a
one storey high glazing system with
vision and opaque sections and
frames that rest on each slab but
have a bypass that covers the slabs
to give an appearance similar to
curtainwall.
• Opaque walls include:
• Mass concrete walls with interior insulation and an elastomeric coating.
• Steel stud backup walls with
rainscreen cladding of some
sort (historically, insulation was
confined to the stud cavity,
more recently having some or
all the insulation outboard of the
exterior sheathing is common
practice).
• Masonry veneer over steel stud
or poured concrete back walls
are increasingly used as architectural accents.
• Roofs are typically protected membrane roofs on concrete slabs.
For the specific project being discussed,
the wall systems being proposed by the
architects could generally be classified
into two basic types, as follows:
• Masonry clad walls supported by
shelf angles at each slab and masonry
ties on 24″ x 16″ centers to steel stud
backup walls. On steel stud walls, a
membrane adhered to the exterior
sheathing acts as the air barrier, vapor barrier and interior moisture
barriers. The primary insulation is
placed outside the membrane and
there may or may not be additional
insulation placed in the stud cavity.
• “Rainscreen” cladding systems made
from metal panels, fritted glass, cement board, or terra cotta supported on z-girts back to the studs of the
back up wall. Again a membrane adhered to the exterior sheathing acts
as the air barrier, vapor barrier and
interior moisture barriers. The primary insulation is placed outside the
membrane and there may or may
Figure 1. Exposed slab edge.
Figure 2. Shelf angle bolted to slab.
Figure 3. Shelf angle on brackets.
Summer/Fall 2008 61
Figure 4. Vertical z-girts.
Figure 5. Thermally Broken Vertical z-girts.
Figure 6. Vertical and horizontal z-girts.
not be additional insulation placed in
the stud cavity. There can be significant
variation in the pattern of framing that
passes through the exterior insulation
depending on the cladding system.
The above wall systems readily transfer to other regions of North America.
Analysis of the effect on thermal performance of the type of alternate cladding attachment and slab edge configuration was
the primary function of our work.
All cases were modeled with both 3 ½″
and 5 ½″ 18 gauge steel stud framing, and
for both insulated and non-insulated frame
cavities. Exterior insulation was modeled
in a range of thicknesses and for several
different insulation types. For each of the
above cases, modeling was also carried out
to determine the effective R-value of regions near concrete slabs. These R-values
were lower than that of the surrounding
wall due to the thermal bridging effect of
the concrete slab.
Modeled slab data was averaged into
the appropriate R-value tables, with the
assumption of 8ft ceilings. The effects of
different slab edge details on overall wall
R-value may be seen in Tables 2 and 3.
Important assumptions made in
the modeling procedure include the
following:
• Exclusion of exterior rainscreen cladding / masonry, due to the complex 3-D
nature of convection and ventilation
through the air gap between exterior
insulation and cladding. Note that it is
the different connection details of exterior claddings that significantly influence
envelope thermal performance, and
not so much the cladding itself, either
masonry or rainscreen. The contribution of either masonry or rainscreen
cladding to envelope thermal performance is not greatly significant.
• Use of a 2-D model, when actual heat
MODELING METHODS
Analysis was carried out using the thermal modeling computer program THERM,
developed and maintained by Lawrence
Berkley National Laboratory. Modeling
was completed for a number of different
steel stud wall systems and cladding support scenarios.
Specific cases that were modeled
included:
Brick veneer:
• With brick bearing on slabs Figure 1.
• With brick bearing on ¼ thick shelf
angles bolted to slabs Figure 2.
• With brick bearing on ¼ thick shelf
angles mounted on 3x ¼ steel brackets
spaced at 24.
Rainscreen cladding:
• With vertical z-girts on 16 centers,
Figure 4.
• With horizontal z-girts on 24 centers.
• With thermally broken vertical z-girts
on 16 centers, Figure 5.
• With vertical z-girts mounted on
horizontal z-girts and two layers of
insulation, Figure 6.
62 Journal of Building Enclosure Design
Figure 7.
Chart 1.
Summer/Fall 2008 63
Table 2: Summary of Effective Thermal Resistances for Walls and Slab Regions (Exterior Insulation Only, No Insulation in
Frame Cavity) (Based on a 2.65m Slab-to-Slab Height
Exposed Concrete Slab or
Balcony
Type of Thermal
Bridging at Slab
Nominal
Wall R-Value
Insulation Thickness (Inches)
33.1
7.0
5.9
5.0
4.2
28.9
24.7
20.5
16.3
12.1
7.9
5.8
Exterior Insulation Placed
Outboard of Slab
3.7
EXPS
6.0
5.0
4.0
3.0
2.0
1.0
0.5
0.0
3.4
2.5
1.7
2.5
0.4
0.0
Spray
foam
Vert. Girts
Hor. Girts
4.9
7.8
9.9
3.5
6.9
8.7
4.2
2.8
2.1
1.4
2.1
0.4
0.0
7.4
6.3
5.7
5.1
5.7
3.4
2.6
9.4
7.9
7
6
7
3.8
2.6
7.0
5.9
4.9
10.6
13.4
24.7
5.0
4.2
3.5
9.1
11.5
28.9
20.5
16.3
12.1
7.9
5.8
6.0
4.0
3.0
2.0`
1.0
0,5
0.0
5.0
3.4
2.5
1.7
0.8
0.4
0.0
4.2
2.8
2.1
1.4
0.7
0.4
0.0
10
8.2
7.3
6.3
4.8
3.8
2.6
Vert. & Hor.
Girts
2” x 1/16”
Brick Ties
11.1
12.1
11.1
9.4
8.5
7.6
6.4
33.1
3.7
¼” thick shelf angle bolted to slab
Mineral
Wool
Effective Wall R-Value for Various Cladding Attachments
(hr·ft2·°F/Btu)
12.1
10.2
9
7.8
6.4
4.8
3.8
2.6
12.6
10.3
9
7.5
5.4
4.2
2.6
31.1
7.0
5.9
4.9
16.8
24.7
5.0
4.2
3.5
13.5
28.9
20.5
16.3
12.1
7.9
5.8
3.7
6.0
4.0
3.0
2.0
1.0
0.5
0.0
flow is in three dimensions. This approximation was necessary due to the
2-D limitation of the software used
(THERM). As a result of the use of a
2-D model, R-values reported for wall
sections containing a combination of
materials represent an approximation
of the actual heat flow path and thermal resistance.
• Steady-state model (ignores thermal
mass).
• Exclusion of membranes, vapor barriers, etc. from the model due to their
negligible thermal resistances.
64 Journal of Building Enclosure Design
5.0
3.4
2.5
1.7
0.8
0.4
0.0
4.2
2.8
2.1
1.4
0.7
0.4
0.0
For those interested in the modeling
process used, email shannonl@matrixgroupinc.net to receive a detailed appendix on modeling procedures, boundary conditions used, calculations and
observations.
INformation transfer
method
We have worked on a variety of ways
of summarizing results of multiple simulation results. We have even created a
simple program which allows the user to
select architectural design features and
15.2
11.6
9.7
7.7
5.3
4.1
2.6
outputs the overall effective R-value of
the assembly. The program utilizes a database of modeled data (from THERM) and
selects the appropriate data for the input
information.
The additional thermal bridging effects of slabs and corner assemblies are
also accounted for by the program. The
user can also input glazing information
(thermal resistance and surface area) if
it is desired to include window area in
the calculation of effective R-value. A
screenshot of the program is shown in
Figure 7.
Most of our architectural clients, however, are not particularly interested in the relative effectiveness of specific details. Their
critical questions are much more fundamental. They think in systems, materials and dimensions. For them we have developed a
tabular method of presenting results.
Modeled output is recorded in tables, presented as the effective R-value
actually reached for a particular nominal R-value (or thickness of insulation).
An architect can select the appropriate
table, depending on wall construction
and slab details, select the R-value closest to that required by specification or
otherwise, and look across the table to
see the necessary insulation thickness
for common insulation types and cladding systems. Alternatively, if the design
type and thickness of exterior insulation
is known, the effective R-value of the assembly for each cladding support style
can be read off, as is shown by the arrows in the sample table below.
Table 2 and Table 3 summarize modeling results for masonry and stud supported cladding systems that consider
insulation material and thickness, cladding
support system and slab edge treatment.
Table 2 presents results for cases where
all insulation is installed outboard of the
stud cavity and Table 3 assumes that there
is an additional 5.5 inches of batt insulation
(nominal R20) in a 5.5” stud cavity.
These tables clearly show the huge
impact thermal bridges have on effective
thermal resistance. The impacts may be
obvious to those familiar with three dimensional heat transfers but are not so
obvious to others.
Some notable observations include:
• When there are major thermal bridges
such as non-thermally broken z-girts,
the effectiveness of insulation is remarkably low to start with, and decreases
with the depth of insulation installed.
This is explainable by noting that when
high heat flow paths exist, reducing the
heat flow of parallel paths will have limited benefit.
• Many building science specialists recommend having all insulation installed
outboard of the stud cavity to help keep
the structural elements warm and dry.
To many practitioners it seems a waste
not to add cheap insulation in the stud
cavity. Comparing Table 4 with Table
3 shows how limited the thermal benefit of stud cavity insulation can be.
• It is interesting that masonry cladding
alternatives can have superior thermal
performance to common rainscreen
panel claddings. This is due, not to their
actual thermal properties, but to the
nature of their attachment to the building with intermittently spaced brick
ties, rather than by continuous sheet
steel components.
• The thermal performance of rainscreen
panel claddings is strongly dependant on
the nature of the structural attachment.
The use of attachments that provide
significant reductions in thermal bridging such as thermally broken vertical zgirts or combined horizontal and vertical z-girts, provide large improvements
in the effective thermal resistances of
wall assemblies.
Clearly there needs to be more attention paid to using cladding support
systems that reduce thermal bridging.
Peer commented on several systems that
could be fabricated or were available
in Europe. One approach to minimizing thermal bridging is to use attachment
methods that minimize the cross sectional area of metal that passes through the
insulation. Another approach is to thermally break the structural components
passing through the insulation.
Summary and conclusions
The modeling completed in this study
has established values for the effective
thermal resistances of common wall systems, and quantified the benefits associated with reducing the amount of thermal bridging elements passing through a
building thermal envelope. This modeling
is hardly innovative. However the presentation of results in a tabular format have
proven to be useful to our architectural
clients on the referenced project and several subsequent ones
It is anticipated that the tables discussed above will prove a useful aid to
architects in meeting design requirements
for thermal performance.
References
ASHRAE. 2005. 2005 ASHRAE
Handbook – Fundamentals, American
Society of Heating, Refrigerating and AirConditioning Engineers, Inc. 2005.
ASHRAE. 2004. ANSI/ASHRAE/IESNA.
Standard 90.1-2004, Energy standard
for buildings except low-rise residential
buildings. American Society of Heating,
Refrigerating and Air-Conditioning
Engineers, Inc. ISSN 1041-2336.
National Research Council of Canada
1995 Canadian National Energy Code for
Buildings.
Peer, L.B.B. 2007 Practical Use of
Thermal Breaks in Cladding Support
Systems Buildings X Conference,
Clearwater Beach, Florida December
2007.
Summer/Fall 2008 65
Table 3: Summary of Effective Thermal Resistances for Walls and Slab Regions (Exterior Insulation + 5.5” Batt Insulation
in 5.5” Frame Cavity) (Based on a 2.65m Slab-to-Slab Height)
Exposed Concrete Slab or
Balcony
Type of Thermal
Bridging at Slab
Nominal
Wall R-Value
Insulation Thickness (Inches)
33.1
7.0
5.9
5.0
4.2
28.9
24.7
20.5
16.3
12.1
7.9
5.8
Exterior Insulation Placed
Outboard of Slab
3.7
EXPS
6.0
5.0
4.0
3.0
2.0
1.0
0.5
0.0
3.4
2.5
1.7
2.5
0.4
0.0
Spray
foam
Vert. Girts
Hor. Girts
4.9
7.8
9.9
3.5
6.9
8.7
4.2
2.8
2.1
1.4
2.1
0.4
0.0
7.4
6.3
5.7
5.1
5.7
3.4
2.6
9.4
7.9
7
6
7
3.8
2.6
33.1
7.0
5.9
4.9
10.6
13.4
24.7
5.0
4.2
3.5
9.1
11.5
28.9
20.5
16.3
12.1
7.9
5.8
3.7
¼” thick shelf angle bolted to slab
Mineral
Wool
Effective Wall R-Value for Various Cladding Attachments
(hr·ft2·°F/Btu)
6.0
4.0
3.0
2.0`
1.0
0,5
0.0
5.0
3.4
2.5
1.7
0.8
0.4
0.0
4.2
2.8
2.1
1.4
0.7
0.4
0.0
10
8.2
7.3
6.3
4.8
3.8
2.6
Vert. & Hor.
Girts
2” x 1/16”
Brick Ties
11.1
12.1
11.1
9.4
8.5
7.6
6.4
12.1
10.2
9
7.8
6.4
4.8
3.8
2.6
12.6
10.3
9
7.5
5.4
4.2
2.6
31.1
7.0
5.9
4.9
16.8
24.7
5.0
4.2
3.5
13.5
28.9
20.5
16.3
12.1
7.9
5.8
3.7
66 Journal of Building Enclosure Design
6.0
4.0
3.0
2.0
1.0
0.5
0.0
5.0
3.4
2.5
1.7
0.8
0.4
0.0
4.2
2.8
2.1
1.4
0.7
0.4
0.0
15.2
11.6
9.7
7.7
5.3
4.1
2.6
Industry Update
BEC Corner
BOSTON
By Jonathan Baron, AIA, Spagnolo Gisness & Associates, Inc.
The Boston-BEC continues to meet monthly (except for
August and December) for one and a half to two hours at
the BSA headquarters in Boston’s Financial District. Recent
presentations have included a review of the jury process for
the first BEC-Boston Award for the Most Innovative Building
Enclosure, Cellulose Insulation by Betsy Petit of Building
Science Corporation, Fall Protection by Brent LaPorte of
Pro-Bel Enterprises, Ltd., and Sound Transmission through
the Building Envelope, by Jeff Fullerton of Acentech, Inc. We
typically have 20 to 30 attendees at our meetings, and there is
always spirited discussion with the presenters.
The BEC sponsored a number of events at Build Boston,
in November 2007, including a presentation of the first BECBoston Award for the Most Innovative Building Enclosure.
Members of the jury reviewed the winning project, 60 Oxford
Street at Harvard University, and members of the project
team described the project and the sensitive treatment of the
building enclosure.
Upcoming meetings will focus on the effects of structural
movement on building enclosures and the interrelationship of
ASHRAE 90.1 and enclosures. More information about our
current initiatives as well as future and past meetings can be
found at our website www.bec-boston.org.
MARYLAND
By H. Michael Hill, AIA, Torti Gallas and Partners, Inc, Fiona
Aldous, Wiss Janney Elstner Associates Inc, and Paul E. Totten,
PE, Simpson Gumpertz & Heger Inc.
Following successful and well attended programs featuring
Understanding Garden Roofs and Selling Them to clients;
Curtain wall Fabrication and Cladding of 1101 New York
Avenue; Wind Information for Ballasted Roofing Systems;
What is Window Wall?; Stone Cladding Design Considerations:
An Overview; and Double Skin Facades, the DC-BEC ended
the year 2007 with a “town hall meeting” to introduce the
new co-chairs and brainstorm the needs and expectations of
our local BEC community.
David A. Harris, FAIA, President of NIBS addressed the
group with accolades to Tim Taylor and Bob Tarasovich for
their devotion to sustaining the council with interesting and
relevant monthly programs since our beginning in February
2005. Harris applauded us for continuing the effort of
providing a means by which the DC, NoVA and MD building
envelope community with interest in the enclosure and
related building science can discuss and obtain information.
A format of quarterly themes will be explored, with the first
series of 2008 addressing “Unnatural Forces” on the building
enclosure. Presentations will explore the relationships and
issues associated with the building enclosure and fire, sound
and blast. Although these events do naturally occur, their
existence beyond the natural poses unique challenges to the
designer to mitigate and control. The January 2008 topic
of fire was presented by Dr. Jonathan Barnett and included
discussion on fire and smoke controls for atria, as well as
design considerations for phased occupancy.
Meetings for the first quarter will continue to convene
at Gensler’s office on the first Wednesday of each month at
4pm.
MINNESOTA
By Judd Peterson, AIA, BEC-Minnesota Co-chair and Jodelle
Senger, AIA, LEED AP, BEC-Minnesota Co-chair
The BEC-Minnesota is preparing for the BEST 1 Symposium
which will be held in Minneapolis, MI on June 10-12, 2008.
Topics and speakers have been selected. We are now in the
process of securing sponsorships from national and regional
companies that have a strong interest in the building enclosure.
We hope that everyone will be able to attend and participate in
this historic event. We also hope that the valuable information
that is learned from this conference can lead to advancements
in both energy efficiency and durability of the building exterior.
Please visit the conference website to find out more about
this exciting event, www.thebestconference.org.
Our local BEC continues to grow as we invite interesting
experts to speak at our monthly meetings. Recent speakers
and topics have included John Edgar of Sto Corporation:
recommended application systems for EIFS stucco; Steve
Pedracine of Minnesota Lath and Plaster: Residential Code
Changes for stucco installations; and Al Gerhke of American
Hydrotech: design and installation of a green roof. BECMinnesota also hosted a seminar at our local AIA Convention
in October 2007. Michael Petermann of Wiss, Janney, Elstner
Associate of New York and Ed Gerns of the WJEA Chicago office
presented “Are Our Building Facades Safe?” that addressed
building facade inspection ordinances. Since we received
such interest in the topic, we continued the discussion at our
November 2007 meeting, inviting the leaders of BOMA so
we could hear their thoughts on the benefits and challenges of
enforcing inspections. BEC-Minnesota has decided to survey
key building owners to try to find a way to better protect the
Summer/Fall 2008 67
68 Journal of Building Enclosure Design
public without negatively impacting the building owner. We
are looking for to what 2008 has to offer.
PORTLAND
By David C. Young, PE, RDH Building Sciences Inc.
After venue hopping each month for the past year, the
Portland-BEC Chapter is happy to announce that our monthly
meetings are now being held at the new Portland Center
for Architecture, office of the AIA. We wish to thank all the
companies that provided space for our meetings over the past
year and additionally, thank all presenters and attendees for
being flexible with the changing venues.
The new AIA Center for Architecture building is a
testament to green design. The existing single story building
was renovated as an example of carbon neutral construction
techniques. The building calculates to be 83 percent below
the current ASHRAE CO2 emissions. The facility will be
used as an educational center for both the design community
and the community at large for environmentally responsible
design. The space suits our needs perfectly and we look
forward to the upcoming seminars we have planned this
year.
The new year is appropriately starting out with green
topics such as passive solar design and day-lighting. Seminar
topics later in the year will focus on roofing and seismic
considerations for brick veneer cladding. We are also planning
a flashing rodeo this summer after witnessing the success of
the Charleston, SC event.
Summer/Fall 2008 69
Buyer’s Guide
Air and Vapor
Barrier
Hohmann and Barnard Inc............................. 12,13
Engineered Curtain
Wall and Window Wall
Old Castle Glass............................................. 36,37
Architects
The Marshall Group.....................................14
Engineers
Sutton Kennerly &
Associates..................................................... 69
Architectural
Glass
Old Castle Glass............................................. 36,37
Architectural Windows
Old Castle Glass............................................. 36,37
Associations
Air Barrier Association
of America .................................................. 8
National Fenestration
Rating Council.............................................. 10
Indoor Air Quality
Association................................................... 2
BEC – New York
Skidmore, Owings & Merrill LLP................... 69
Below Grade Water,
Insect and
Containment
Barrier
Polyguard........................................................ 4
Building Enclosure
Construction Consulting
International................................................. 34
Building Enclosure Consultants
The Façade Group LLC................................. 17
Building Safety
International Code Council............................ 62
Building Sciences and Restoration
Consultants
Read Jones
Christoffersen Ltd........................................ 59
Commercial Insulation
Thermafiber Inc.............................................. 3
Consulting, Commissioning,
Engineering, Testing,
Certification and
Inspections
Architectural Testing...................................... OBC
Diagnostic Tools
The Energy Conservatory.............................. 73
70 Journal of Building Enclosure Design
Entrance Systems Space
Parts
Old Castle Glass............................................. 36,37
Exterior Sheathing
National Gypsum
Company...................................................... 75
Glass Association
The Glass Association.................................... 74
Insulation
Manufacturer
Demilec USA.................................................. 35
Jag Architectural
Judd Allen Group............................................ 68
Masonry
Morter Net USA Ltd...................................... 56
Mineral Wool Insulation
Roxul Inc......................................................... 6
Rainscreen stuco Assembly
Stuc-O-Flex.................................................... 26
Structural Engineering
Design and Consulting
Simpson Gumpertz & Heger.......................... 65
Structural Engineering
Design and Consulting
WJE................................................................. 42
Structural Engineers
Thornton Tomasetti....................................... 19
Technical and
Educational
Consultants
SpecGuy......................................................... 48
Water Intrusion Test
Equipment and Training
The RM Group............................................... 24
Water Proofing
STO Corporation........................................... 38
Thermal Performance of the Exterior
Envelopes
of Whole Buildings XI International
Conference
Call for Papers & Workshops
Abstracts Due May 11, 2009
The eleventh international conference on Thermal Performance of the Exterior Envelopes of Whole Buildings XI will be held
December 5–9, 2010. This conference will present two tracks:
PRINCIPLES – Devoted to Research
PRACTICES – Focusing on Practical Applications and Case Studies
You are invited to submit an abstract for presentation in either the Principles (research) or Practices (practical applications)
track. Special topic Workshops will be presented before or after the conference. A written paper will be required for all
presentations in the Principles track. Papers are encouraged for all presentations, but not required for the Practices track.
ABSTRACT SUBMISSION
Please submit an abstract, not to exceed 250 words, by May 11, 2009 to:
Pat Love
Oak Ridge National Laboratory
1 Bethel Valley Road
P.O. Box 2008, Building 3156
Oak Ridge, TN 37831–6067
Phone: 865-574-4346 Fax: 865-574-9331
Email: lovepm@ornl.gov
Suggested Paper and Presentation Topics
Dates to Remember
Building Retrofit
Building Sustainability–Green Buildings
Commissioning and Test Procedure Development
Daylighting
Design Tools
Disaster Design for Hurricanes & Earthquakes
Durability and Service Life
Dynamic Envelope Performance (Mass)
Envelopes: Walls, Roofs, Attics, and Foundations
Factory-built Housing
Fenestration
Indoor Environment
Insulation Air Barriers and Vapor Retarders
Integrated Envelopes
Moisture Issues
Monitoring, Modeling, and Simulation
Passive Solar Design
Standards, Codes, and Guidelines
Weatherization
Whole-building Efficiency
Zero Energy Buildings
!
!
!
!
!
!
!
!
May 11, 2009
Abstracts due to lovepm@ornl.gov
July 20, 2009
Notification of abstract acceptance to Authors
January 15, 2010
Authors submit completed manuscripts to Session
Chairs for peer review
March 29, 2010
Peer review comments sent to Authors. At this time,
Authors are encouraged to provide updated research
data, with the concurrence of the Session Chair.
June 18, 2010
Final draft of papers and updated abstracts are due
to Session Chairs
August 31, 2010
Papers returned to Authors with ASHRAE’s editing
September 17, 2010
All papers must be returned in final form to ASHRAE
for publication
December 5–9, 2010
Conference dates
For more information, please visit our web site at: www.ornl.gov/sci/buildings/2010/index.shtm
Summer/Fall 2008 71
Membership
JOIN BETEC
Building Enclosure Technology and Environment Council
1090 Vermont Avenue, NW, Suite 700 | Washington, DC 20005-4905
Tel: (202) 289-7800 | Fax: (202) 289-1092 | www.nibs.org/BETEC
To become a member of the Building Enclosure Technology and Environment Council,
please complete and return the following application form:
Name: ______________________________________________ Title: ___________________________________________________
Company: ______________________________________________ Address: _____________________________________________
City: ______________________________________________ State: _________________ ZIP Code: _________________________
Telephone: ______________________________________________ Fax: ________________________________________________
E-Mail Address: __________________________________________
MEMBERSHIP CATEGORY:
c Individual Member - $100
cCorporate Member - $250
(optional alternate member)
RESEARCH COORDINATING
COMMITTEES:
I will participate on the following Research
Coordinating Committees (RCC’s):
c Heat Air and Moisture
c Fenestration
c Membranes
c Materials and Resources c Existing Building Enclosures
DUES PAYMENT:
c Check or Money Order enclosed payable to BETEC
c Education
c Window Security Rating and Certification System
OPERATIONAL COMMITTEES:
I will participate on the following
Operational Committees (OC’s):
c Technology Transfer
c National Program Plan
cPlease bill my Credit Card: c AMEX
c MC
c Network for the Advancement of
Building Science
ALTERNATE MEMBER
INFORMATION
(corporate members
only):
Alternate Name:_________________
Alternate Title:_ _________________
Alternate’s RCC’s and OC’s:_ ______
______________________________
c VISA
Account No. ___________________________________________________ Exp. Date _________________________
Cardholder’s Name _____________________________________________ Billing Address ________________________________________________
City __________________________________________ State _____________ ZIP ___________________________
Signature ______________________________________________________ Date _____________________________
JOIN NIBS
National Institute of Building Sciences
1090 Vermont Avenue, NW, Suite 700 | Washington, DC 20005-4905
Tel: (202) 289-7800 | Fax: (202) 289-1092 | www.nibs.org
Membership Application
Membership in the National Institute of Building Sciences is open to all interested parties as provided in the enabling legislation. Individuals are eligible to become either public interest or industry sector members. Organizations that wish to support the Institute in achieving
its objectives may become sustaining or contributing organization.
Name ______________________________________________ Title ___________________________________________________
Company ______________________________________________ Addres _____________________________________________
City ______________________________________________ State _________________ ZIP Code _________________________
Telephone ______________________________________________ Fax ________________________________________________
Nature of Business/interest areas: _________________________________________________________________________________
c INDUSTRY SECTOR MEMBER:
Open to any individual in the following categories: Building construction;
labor organizations; home builders;
building or construction contractors;
producers, distributors or manufacturers of building products; trade and
professional associations; organizations engaged in real estate, insurance or finance; research and testing
of building products; and code and
standard organizations. ANNUAL
CONTRIBUTION: $150
c PUBLIC INTEREST SECTOR
MEMBER: Open to any individual
in the following categories: Federal, state and local government,
consumer organizations, nonprofit
research and educational organizations, the media, architects,
professional engineers or other
design professionals, and retirees.
ANNUAL CONTRIBUTION: $75
c SUSTAINING ORGANIZATION: Open to organizations in
the public interest or industry sectors desiring to provide additional
support for and participation with
the Institute to achieve the goals
and objectives. Sustaining organizations may designate up to five
individuals from their organization
to be Institute Members. ANNUAL
CONTRIBUTION: $1000
Annual Contribution $ __________________________ c Payment Enclosed
c Bill Me
c Charge to my MC/VISA/AMEX:
Account No. __________________________________________ Exp. Date_______________ Name on Card _____________________________________________
Billing Address _________________________________________________________________
The National Institute of Building Sciences is a nonprofit organization with an Internal Revenue Service Classification of 501(c)(3) tax exempt status. Contributions to all 501(c)(3) organizations are tax
deductible by corporations and individuals as charitable donations for federal income tax purposes.
Signature ____________________________________________ Date ___________________________
Summer/Fall 2008 75
76 Journal of Building Enclosure Design