Balancing Modified Bitumen
with High SRI Ratings
Name
Scott Ballard RRC, RRO
Vice President Technical & Consultant Services
DERBIGUM
AIA/CES
• DERBIGUM is a Registered Provider with
The American Institute of Architects
Continuing Education Systems.
• Credit earned on completion of the program
will be reported to CES Records for AIA
members.
• Certificates of Completion for non-AIA
members are available on request.
AIA/CES
• This program is registered with the AIA/CES for
continuing education.
• As such, it does not include content that may be
deemed or construed to be an approval or
endorsement by the AIA of any material of
construction or any method or manner of handling,
using, distributing, or dealing in any material or
product.
• Questions related to specific materials, methods,
and services will be addressed at the conclusion
of this presentation.
Learning Objectives
Upon completion of this program, participants will be able
to:
• Define reflectivity, emissivity and Solar Reflectance
Index (SRI).
• Identify some of the key organizations in setting the
standards for a “cool roof”.
• Identify some of the advantages of a high SRI roofing
system.
• Understand the importance of balancing high SRI with
sustainability and longevity.
• Discuss additional design consideration for a high
performance roofing system.
• Review alternative systems.
Defining the Cool Roof
•
Reflectivity
– The ratio of the energy of a wave reflected
from a surface to the energy possessed by
the wave striking the surface.
•
Emissivity
– The ratio of the radiation emitted by a
surface to the radiation emitted by a
blackbody at the same temperature.
Defining the Cool Roof
• Solar Reflectance Index (SRI)
– A measure of the roof's ability to reject solar heat, as
shown by a small temperature rise.
– Standard black (reflectance 0.05, emittance 0.90) is 0
and a standard white (reflectance 0.80, emittance
0.90) is 100.
– By definition, particularly hot materials can even take
slightly negative values, and particularly cool
materials can even exceed 100.
Setting and Reporting the
Standards
• Cool Roof Ratings
Council (CRRC)
– The CRRC was created in
1998.
– Develop accurate and
credible methods for
evaluating and labeling the
solar reflectance and
thermal emittance of
roofing products.
– Disseminate the
information to all interested
parties.
Setting and Reporting the
Standards
• EPA Energy Star
– ENERGY STAR qualified
roof products (0.65
reflectivity) reflect more of
the sun's rays.
– ENERGY STAR qualified
roof products can help
reduce the amount of air
conditioning needed in
buildings.
– ENERGY STAR qualified
roof products can reduce
peak cooling demand by
10–15 percent .
Setting and Reporting the
Standards
• Title 24
– Cool roofs are highly reflective
(0.70), highly emissive (0.65)
roofing materials that stay 50
to 60 degrees F cooler.
– For building owners they can
cut maintenance costs and
increase the life expectancy of
the roof.
– A calculator is now available
to quickly determine the
energy-equivalent R-value of
insulation needed to meet Title
24 requirements.
Setting and Reporting the
Standards
• Leadership in Energy &
Environmental Design
(LEED)
– The LEED Green Building
Rating System is a
voluntary standard.
– LEED NC requires 75% of
the roof to be a cool roof.
– The SRI value (minimum
78) is calculated according
to ASTM E 1980,
Setting and Reporting the
Standards
• American Society of Heating,
Refrigerating and AirConditioning Engineers (ASRAE)
–
ASHRAE 90.1 defines a cool roof as
having a minimum solar reflectance of
0.70 and minimum thermal emittance of
0.75.
–
Allows reduced roof insulation (U-factor) if
a cool roof is used.
–
These documents are not mandatory or
enforceable until a jurisdiction adopts the
documents as part of regulation or law.
• Proposed standard 189.1
–
To be SRI 78 (low-slope)or cool roof.
–
A “cool roof” is just one of the potential
strategies for reducing heat gain to a
building structure.
–
Modeled after LEED NC v. 2.2.
Setting and Reporting the
Standards
• State, County & City
Regulations
– Some “Talk the Talk”
• Atlanta & Houston Studies
– Others “Walk the Walk”
• California & Chicago
• Utility Companies
– Incentives or Rebates.
– Improvement over existing
reflectivity or SRI.
– Some require minimum
insulation in coordination with
cool roof.
Setting and Reporting the
Standards
•
Laboratory Studies
– Oak Ridge National Laboratory
• Reflectivity research, begun in the
summer of 1997
• Typical results are that reflectance
is reduced by about 0.1 to 0.3.
• Most recent studies explored
effects of R-Value to offset energy
in Northern climates.
– Lawrence Berkeley National
Laboratory
• The Heat Island Group.
• Buildings used up to 40% less
energy for cooling than buildings
with darker roofs.
Why Cool Roofing
• Heat Island Effect
– A "dome" of elevated
temperatures over an
urban area.
– Caused by structural and
pavement heat fluxes, and
pollutant emissions.
– The annual mean air
temperature of a city with 1
million people or more can
be 1.8–5.4°F (1–3°C)
warmer than its
surroundings.
Why Cool Roofing
• Heat Island Effect
– In the evening, the
difference can be as high
as 22°F (12°C).
– Heat islands can affect
communities by increasing:
• Summertime peak energy
demand;
• Air conditioning costs;
• Air pollution;
• Greenhouse gas
emissions;
• Heat-related illness and
mortality;
• Water quality.
Why Cool Roofing
• Heat Island Effect
– Original Atlanta Study
focus:
• The development of the
urban heat island
phenomenon.
• Change on air quality.
• Surface energy budget
characteristics across
the Atlanta urban
landscape.
Why Cool Roofing
• Heat Island Effect
– New Atlanta Study
• The study indicates a
connection between the
intensity of the 2008 urban
Atlanta tornado and the
heat island effect.
• Hot, dry urban conditions
may have led to a larger
discrepancy with the
surrounding atmospheric
conditions, enhancing
stability and thus
intensifying the storm as it
approached the city.
Why Cool Roofing
• Heat Island Effect
– Ambient Temperature at
Night
• Normal forests and fields
in Georgia during the day
would be a mustard green,
not the hot red that is seen
in the upper photo.
• At night it would be a cool
green, not the mustard
green/orange seen in the
bottom photo.
• This has nothing to do
with global warming and
everything to do with land
use changes
Why Cool Roofing
• Heat Island Effect
– Urban Heat Related Deaths
• Compared to rural areas,
cities experience higher rates
of heat-related illness and
death.
• Heat islands can amplify
extreme hot weather events,
which can cause heat stroke
and lead to physiological
disruption, organ damage,
and even death.
• Especially in vulnerable
populations such as the
elderly.
Why Cool Roofing
• Energy Savings
– Quantify Savings Potential
• A lower temperature means the roof conducts less heat into
the building, which translates into a smaller cooling load.
• A reasonable average savings expectation for a typical
application of cool roofing is in the range of 10 percent to 30
percent of the cooling energy required.
• This range might equate to a total building electric bill
reduction of 3 percent to 10 percent.
Why Cool Roofing
• Energy Savings
– Peak Energy Production Savings
• Because cool roofs reduce air-conditioning use during the
day’s hottest periods, the associated energy savings occur
when the demand for electricity is at its peak.
• Use of cool roofs reduces the stress on the energy grid
during hot summer months and helps avoid shortages that
can cause blackouts or brownouts.
• For building owners that pay for their energy based on the
time of use, they save energy when it is at its most
expensive.
Modified Bitumen Reflective
Options
• Coated Granules
• Paint Chips
• Laminate Sheets
• Integrated Reinforcement Sheet
Modified Bitumen Reflective
Options
• Coated Granules
– Pros
• High initial reflectivity
– Cons
• Granule loss
• Recoat needed 4-7
years
• Asphalt oil migration
• Paint Chips
– Pros
• Factory applied
– Cons
• Light refraction
• Flaking
• Asphalt oil migration
Modified Bitumen Reflective
Options
• Laminate Sheet
– Pros
• High initial reflectivity
• Factory applied
• Increased puncture
resistance
– Cons
• Wrinkled appearance
• Durability question
• Integrated Surface
– Pros
• High initial reflectivity
• Factory applied
• Increased puncture
resistance
• PH Neutral impact on H2O
• Opportunity for recover
• Foot traffic protection
– Cons
• Application time
• Application care
SRI Not the Whole Story
• Life Cycle Costs
– Proven In Place Performance
• Membrane Thickness
• Redundancy
White Cap Sheet - 140 mils
Base Sheet
- 120 mils
Adhesive
30 mils/layer
SRI Not the Whole Story
• Life Cycle Cost
DERBIGUM Sustainable Roofing Program
Life Cycle Cost Analysis
PROJECT INFORM ATION
Project Name
Square Feet of Project
Sustainable Guaranty Length, Years (30 or 40)
DERBIGUM System Type, Initial
DERBIGUM System Cost, Initital per Square Foot
DERBIGUM Recover Cost, per Square Foot
Alternative System Type
Altenative System Cost, Initial per Square Foot
Alternative System Life Span (15 or 20)
Annual Inspection Cost, Base Rate
Inflation Rate
Joe The Owner
75,000
40
$9.00
$4.00
$7.50
20
$750.00
5%
SRI Not the Whole Story
• Life Cycle Cost
CURRENT COST ANALYSIS
DERBIGUM System Life Cycle Cost Analysis
Initital Roof Replacement Cost
Annual Inspection Cost
Maintenance & Repair Cost
DERBIGUM Sustainable Membrane Cost
DERBIGUM System Total Cost
Alternative System Life Cycle Cost Analysis
Initital Roof Replacement Cost
Maintenance & Repair Cost
Alternative System Roof Replacement Cost
Alternative System Total Cost
Total Savings with DERBIGUM System
Lump Sum Square Foot
$675,000.00
$9.00
$15,000.00
$0.20
$300,000.00
$990,000.00
$4.00
$13.20
$562,500.00
$7.50
$562,500.00
$1,125,000.00
$7.50
$15.00
$135,000.00
$1.80
SRI Not the Whole Story
• Life Cycle Cost
INFLATION ADJUSTED ANALYSIS
DERBIGUM Life Cycle Cost Analysis
Initital Roof Replacement Cost
Annual Inspection Cost
Maintenance & Repair Cost
DERBIGUM Sustainable Membrane Cost
DERBIGUM System Total Cost
Alternative System Life Cycle Cost Analysis
Initital Roof Replacement Cost
Maintenance & Repair Cost
Alternative System Roof Replacement Cost
Alternative System Total Cost
Total Savings with DERBIGUM System
Lump Sum Square Foot
$675,000.00
$9.00
$19,750.00
$0.26
$758,085.06
$1,452,835.06
$10.11
$19.37
$562,500.00
$7.50
$1,421,409.48
$1,983,909.48
$18.95
$26.45
$531,074.43
$7.08
SRI Not the Whole Story
• But it is a New Chapter to the Life Cycle Cost
Story
20 year Life Cycle Cost
Black Roof Surface
White Roof Surface
Roof Size
Roof Product Cost
Install (Labor & Overhead)
Tear-Off (Disposal Costs)
Est. Maintenance 20 Year
Est. Repair Cost 20 Year
50,000 Square Ft.
$70,000.00
$60,000.00
$12,500.00
$5,000.00
$7,750.00
50,000 Square Ft.
$88,000.00
$45,000.00
$0.00
$1,500.00
$0.00
Est. Energy Savings 20 Year
Est. Lifecycle Costs
$0.00
$155,250.00
[$84,000.00]
$50,500.00
adjusted from Cool Roofing Fall 2006 p. S15
SRI Not the Whole Story
• Safety
– Fire Rating
• Is it an additive?
• Is it integrated?
– Slippery When Wet
• OSHA
• Contractor Insurance
SRI Not the Whole Story
• Additional Considerations
– PH Neutrality
• Capture water run-off for ecological benefits
• Provides greater ROI
SRI Not the Whole Story
• Additional
Considerations
– Algae & Fungus
Resistance
– Grease & Chemical
Resistance
Design Consideration
• Staged Installation
– Make the building weathertight.
– Stage to optimize “bright white” for aesthetics and
performance.
Design Consideration
• Positive Slope
– Avoid ponding water for premature failure.
Design Consideration
• Location and
Orientation of Building
– Bright White roofing
system can cause
glare on neighbors.
– Building layout can
optimize energy
efficiency on new
construction.
Alternative Cool Options
• Ballasted Roofing
Systems
– Studies
• Oak Ridge National
Laboratory/SPRI
– Pros
• Alternate to Traditional
Cool Roofing
• Cheap for
Manufacturers to
Promote
Alternative Cool Options
• Ballasted Roofing
Systems
– Cons
• Roof Weight
• Projectile in High Wind
Regions
• Scouring
• Sharp shale can penetrate
roofing membrane
• Dirty & promotes
unwanted plant growth
• Costly Re-roof
– Acceptance
• City of Chicago
• Title 24
Alternative Cool Options
• Vegetated Roofing
Systems
– Studies
• Multiple in US & Europe
• Current University of
Washington
• Michigan State University
– Pros
• Improved Air Quality
• Improved Storm Water
Management
• Mitigation of Heat Island
• Increased Roof Life
Alternative Cool Options
• Vegetated Roofing
Systems
– Cons
•
•
•
•
Weight of system
Maintenance
Upfront cost
Intensive system roof
maintenance
– Acceptance
•
•
•
•
City of Chicago
New York City
Portland, Oregon
LEED
Alternative Cool Options
•
Insulation Offset
– Studies
• PIMA
• Oak Ridge National Laboratory
– Pros
• in addition to reflectivity, roof
insulation (measured by the Rvalue) plays an important role in
building energy consumption for
heating and cooling.
• The colder the climate, the greater
the need for a higher R-value to
ensure that less heat is lost from
the building envelope.
• increasing the thickness of polyiso
insulation on a roof deck
significantly reduces energy costs
while providing a positive rate of
return on the cost of installation.
Alternative Cool Options
•
Insulation Offset
– Cons
• Implementation could take 3 – 5
years.
• Rated R value often not
accomplished in real life
application.
• Over insulating equals no extra
benefit and could cause opposite
effect on efficiency.
– Acceptance
• No uniform acceptance to date.
• Various utility companies combine
with reflective roofing rebates.
• ASHRAE 90.1: 2007 first increase
since 1998.
Conclusion
• Defined “cool roofing” through reflectivity, emissivity and
the Solar Reflectance Index.
• Recognized key organizations in the standards or
reporting arenas.
• Identified some of the reasons for the emergence of cool
roofing including Heat Island Effect and Energy
Efficiency.
• Discovered the benefits of a high SRI roofing system.
• Discussed additional characteristics that should be
considered and design considerations to optimize your
roofing system.
• Identified Alternative systems to the traditional white cool
roofing system.
DERBIGUM would like to
thank you for this opportunity.
Questions?
Scott Ballard RRC, RRO
Vice President Technical & Consultant
Services
DERBIGUM
www.derbigum.com
www.epgen.com
info@derbigum.com