Low-Cost Methods for Reducing Heating Consumption in FSILGs at MIT
by
Steven J. Stoddard
Submitted to the Department of Mechanical
Engineering in partial fulfillment of the requirements for the
Degree of
Bachelor of Science in Mechanical Engineering
at the
MASSACHUSETTS INSTfUTE
OF TECHNOLOGY
Massachusetts Institute of Technology
AUG 0 2 2006
June 2006
LIBRARIES
© 2006 Steven J. Stoddard. All rights reserved.
The author hereby grants to MIT permission to reproduce and to distribute publicly paper
and electronic copies of this thesis document in whole or in part in any medium now
known or hereafter created.
Signature of Author.....................................
...............
'Depar'tent of Mechanical Engineering
May 12, 2006
Certified
by............................ . .,.....:..............
Leon Glicksman
Professor of Architecture and Mechanical Engineering
Thesis Supervisor
Accepted by
.
.....
.............
..................
;
air
...
John H. Lienhard V
,Undergraduate Thesis Committee
ARCHIVES
Low-Cost Methods for Reducing Heating Consumption in FSILGs at MIT
by
Steven J. Stoddard
Submitted to the Department of Mechanical Engineering
on May 12, 2006 in partial fulfillment of the requirements for the Degree of
Bachelor of Science in Mechanical Engineering
Abstract
Rising energy prices and increasing price volatility present a problem for many
fraternities, sororities, and independent living groups (FSILGs) at MIT. The buildings
they occupy are typically quite old, with little insulation and leaky building envelopes,
resulting in unnecessary heating energy consumption and expenditures, as well as CO2
emissions. Through simple retrofitting procedures, these levels of consumption,
expenditures, and emissions could be greatly reduced. If such measures are
implemented, FSILGs would be in a strong position to lead the way in helping MIT to
achieve its recently announced emissions reduction goals. To determine the extent of
reduction that could be realized, several easy retrofitting measures have been applied in
one FSILG, and the resulting consumption has been compared with previous levels.
To properly make that comparison, a background of FSILG buildings, their
characteristics, and their uses are outlined. Then, the specific retrofits installed are
described in detail. After that, the resulting changes in consumption efficiency are
examined and compared to historical records. In summary, those findings show a 32%
improvement in consumption efficiency, from a pre-retrofit average of 1.07 therms per
heating degree day (HDD) to a post-retrofit average of 0.73 therms/HDD. In analyzing
these results, it is estimated that $1543 are saved on heating costs, and that CO2
emissions are reduced by 4500 lbs/yr. Finally, given these results, recommendations are
made for installing similar retrofits in other FSILGs, and the potential impact of those
actions are assessed.
Thesis Supervisor: Leon Glicksman
Title: Professor of Architecture and Mechanical Engineering
2
Table of Contents
Introduction....................
...
.........
..................
Background...........................................................................
......... ........................................
4
..............................................
5
Building Characteristics ......................................................................................................
6
R etrofit ..............................................................................................................................
15
R esu lts...............................................................................................................................
23
Discussion.........
.
............
.........
...................... ..................
. ...... 25
Conclusions and Recommendations ...........................................................
References ..................
....................................
27
... 3.........0.........
30
Appendix...........................................................................................................................
31
Figures
Figure 1. Second floor plan showing locations of window and door retrofits .................... 9
Figure 2. First floor plan showing locations of window and door retrofits ...................... 10
Figure 3. Ground floor plan showing locations of window and door retrofits ................. 11
Figure 4. Five natural gas-fired furnaces provide heat for hot water and central heating 12
Figure 5. Electrical dial and control valve for baseboard heaters .................................
13
Figure 6. Baseboard heater with fins and enclosure under normal operation ................... 13
Figure 7. Three hot water storage tanks............................................................................
14
Figure 8. Plastic window sheeting retrofit in dining room. Caulking cord and wooden
blocks are in place at bottom to close off large gaps ................................................ 16
Figure 9. Retrofit on back door .......................................................................................
18
Figure 10. Social room thermostat settings.......................................................................
20
Figure 11. Living room thermostat settings......................................................................
20
Figure 12. Dining room thermostat settings ........................................
21
Figure 13. Library thermostat settings ........................................
...................
...................
21
Figure 14. RiteTemp programmable thermostat installed in common rooms .................. 22
Figure 15. Natural gas consumption and efficiency per month ........................................ 24
3
Introduction
Over the last 7 years, residential natural gas prices in Massachusetts have increased from
an average of $9.28 per thousand cubic feet in 1999 to $16.26 per thousand cubic feet in
2005. In addition to this general rise in prices, short-term volatility has become a major
problem. Since 2001, prices have changed from month to month by several dollars or
more with increasing frequency. For instance, from June to July of 2005, natural gas
prices jumped from $13.74 to $16.09 in the span of one month. Fortunately, this spike
occurred during the summer when consumption was low, but prices only climbed as the
winter months approached. Such volatile energy prices are, in part, a measure of the
instability of fossil fuel resources, whether it comes from the politics of Middle Eastern
countries or natural disasters in the Gulf Coast. This instability, along with global
environmental concerns, has renewed U.S. interest in seeking alternative energy
resources and reducing current energy consumption.
Recently, MIT has taken a heightened role in addressing these global energy issues. In
June of 2005, MIT established the Energy Research Council (ERC) to provide a
framework guiding energy research at the Institute, in the areas of technology,
economics, and policy. In their report that was released in May, 2006, the council
described the importance for MIT to be able to lead by example through implementing
sustainable practices throughout its campus. In particular, the goals of increasing campus
energy efficiency and fostering student activism for energy-sustainable living were cited.
Currently, utility emissions account for 93% of MIT's total greenhouse gas (GHG)
emissions, and it is the Institute's goal to achieve GHG emissions in 2015 equal to or
lower than the value today, even as the campus continues to grow. Clearly, the most
effective way to accomplish this task will be to reduce utility emissions.
According to the ERC report, residential and commercial buildings consume about 40%
of all primary energy in the U.S. If this consumption could be reduced, utility emissions
could drop significantly as well. At MIT, residential utility emissions account only for
dormitories on campus, when in fact the 25% of the student population living off-campus
extends MIT's emissions impact even further. Students in off-campus housing also face
utility costs directly, without the insulation from fuel price volatility provided by MIT
housing subsidies. As a result, off-campus students are in a unique position to reap
immediate financial reward for reducing energy consumption in their own living spaces,
and this study will look at the possibilities of doing just that.
Through implementation of low-cost, thermal energy-saving methods in an off-campus
fraternity, this study will examine the degree of reductions in both cost and consumption
that can be achieved in a high-density, high-energy-intensity college housing
environment. Impacts of such methods will also be observed on human comfort, and the
experiment will be assessed for repeatability and expected impacts in other fraternities,
sororities, and independent living groups (FSILGs) at MIT. Further, such investigation
could provide insights into what might be the most easily performed and beneficial
energy-saving methods for campus dormitories as well.
4
Background
FSILG Characteristics
Approximately 25% of MIT undergraduates live in FSILGs, which are located mostly in
Boston. In the 2004-2005 school year, such residences housed anywhere from thirteen to
forty-three students, with the average number of occupants at twenty-nine. Compared to
campus dormitories, most FSILG houses are older, often more than sixty years old. The
students who live in them usually provide the necessary upkeep and repairs, which
sometimes results in a lack of proper weatherization measures. FSILG houses, like
dormitories, are also used around the clock. Lights are typically turned on 24 hours a
day, and appliances like washers and dryers, microwaves, and stoves see extensive use.
Such intensive energy use can lead to greater monthly expenditures as compared to
regional and national averages, indicated in Table 1 below.
Table 1. Energy Expenditures for FSILGs Compared to New England and U.S. Averages
FSILGs
New England
U.S.
Total Expenditures
$1.25 million
$10.87 billion
$176 billion
Expenditures per sq.
Foot
$3.23
$1.89 (built before
1939)
Total Expenditures
per Household
$1,245
$794$718
(built before
Member
Northeast and U.S. Data from Energy Information Administration, 2001 Residential Energy Consumption
Survey, http://www.eia.doe.gov/emeu/recs/recs2001/detailcetbls.html
FSILG Total Expenditures from MIT FSILG Office, Fall 2004 and Spring 2005 FTP reports
All values are reported in 2005 dollars.
It can be seen here that FSILGs spend roughly 50% more on energy, per person, than do
residents of similar-aged homes around the country. Comparing their costs with New
England data verifies that these higher expenditures result from greater levels of
consumption, rather than from higher energy prices. Additionally, human comfort is
often an issue in FSILGs as well. For instance, one common complaint in many FSILGs
is that residents have very little control over the temperature in their rooms, and many
keep their windows open throughout the winter as a result. Clearly, this is one action
which leads to greater consumption, and in turn, unnecessary utility emissions. But taken
together, these three factors - higher consumption, greater energy expenditures, and low
levels of comfort in the home - make FSILG buildings ideal locations for launching
energy-saving measures.
5
Energy Saving Actions and Technology
There are a number of changes, both behavioral and technological, that can be
implemented in buildings in order reduce energy consumption and costs. Examples of
simple behavioral changes include shutting off lights and fans in rooms that are not in
use, and setting heating systems to lower temperatures, or even not turning them on, until
later in the winter season. Similarly, technological upgrades could be implemented to
reduce energy use and, perhaps, improve comfort as well. Examples of these include the
installation of weather stripping, wall and attic insulation, and programmable thermostats.
Yet another option, though slightly more expensive, is to replace old boilers or water
heaters with more efficient models.
In order to determine the effectiveness of such improvements, one FSILG was selected
for installation of weatherization measures during the 2005-2006 winter heating season.
The resulting gas bills were then compared with historical records to examine changes in
heating efficiency.
Building Characteristics
Two important aspects of this study were to examine a structure similar to most FSILGoccupied buildings at MIT, and to have easy access to the building for implementing
energy saving methods. Taking these factors into account, a large, six-story brownstone
located at 97 Bay State Road, near Boston's Kenmore Square, was selected. Like many
FSILG buildings, this one serves as an MIT fraternity house from September to May,
while rooms are temporarily rented out to area college students from June to August.
Throughout the year, occupancy is usually around 35 people at any given time, with the
exception of school holidays and moving periods.
In many dormitories, and in most FSILG's, living arrangements consist of shared
amenities, such as kitchen and bathroom facilities, and individual sleeping quarters. In
this study, shared house amenities included a kitchen, a pantry, and a social room in the
basement; a dining room, a living room, and another, smaller pantry on the first floor; a
library on the second floor, and another living room on the fifth floor. While these
amenities and social rooms were shared by all house occupants, the sleeping quarters, and
the study areas contained within them, were shared only by the residents of each
bedroom. The bedrooms were distributed throughout the house and ranged in size from
one to four occupants. All rooms, their occupancy, and heating methods are listed in
Table 2 below.
6
Table 2. Room Sizes and Heating Types
Room (Quantity)
Occupancy
# Windows
Heating Type
Ground Floor
Social Room (1)
Bedroom (1)
1
2
2
Pantry
Kitchen
Central heat
Hot water baseboard heater
None
None /Gas stove burners
FirstFloor
Living Room (1)
Dining Room (1)
Bedroom (1)
3
3
1
1
Pantry
1
Central heat
Central heat
Hot water baseboard heater
None
SecondFloor
Bedroom
Bedroom
(1)
(1)
Central heat
Hot water baseboard heater
Hot water baseboard heater
3-4
4
3
1
1
3-4
3
2
2
1
3
Hot water baseboard heater
Hot water baseboard heater
Hot water baseboard heater
3-4
1
5
2
Hot water baseboard heater
Hot water baseboard heater
1
6
2
1
Hot water baseboard heater
Hot water baseboard heater
None
Library (1)
ThirdFloor
Bedroom
(1)
Bedroom (2)
Bedroom (3)
FourthFloor
Bedroom (2)
Bedroom (2)
Fifth Floor
Bedroom (6)
Bedroom (1)
Living Room (1)
Like most FSILG houses, the one in this study was around 100 years old. It was
constructed in 1901 from a wood and metal frame, and made up just over 11,000 square
feet, compared to the FSILG average of 10,850. As was common in many buildings
constructed in the early 1900s, the interior walls and ceilings were made of plaster, while
the exterior walls were brick. The west wall was shared with the building next door,
which also happens to be an MIT FSILG; the remaining three exterior walls were
exposed to the environment, and were found to have little or no insulation. Some
insulation had been found in the walls during renovation projects, but it consisted
primarily of old newspapers and plaster.
7
One common feature in many MIT FSILG's is a central staircase running throughout the
height of the house. These central shafts allow warm air to rise more easily than in
typical homes or apartments, and can lead to greater rates of heat loss through the roof.
In the case examined here, two shafts ran vertically through the house, the larger of
which contained a central staircase, an old elevator shaft, and a smaller back staircase.
The second shaft contained an old light shaft. Both shafts can be seen in the second and
first floor plans shown in Figures 1 and 2, where it should be noted that closets on each
floor have been built into the elevator and light shafts, impeding the flow of air from
below. Figure 3 shows the ground floor plan as well. When warm air does reach the top
of the house, however, proper insulation can help reduce the rate of heat loss through the
roof. In this house, a small crawlspace existed between the ceiling of the top floor and
the roofline, where an adequate amount of loose-fill rock wool insulation - approximately
11" - was present.
Aside from air circulation within the house, it was necessary to have an understanding of
the airflow into the house from outside. For many buildings, the primary locations for
heat exchange with the environment are through windows and doors. In this study, there
were two doors at opposite ends of the house, one each on the north and south sides. The
north side door, measuring 1.75" thick, was made of hollow steel and set into a metal
frame. On the opposite end of the house was the main door, slightly thicker at 2" and
made of solid wood, set into a wooden frame. Both doors were found to have small
cracks or gaps between the door and the frame, especially along the bottom and on the
sides opposite the hinges. Both doors opened into an entryway with an outer door as
well. Like the doors, all of the windows in the house were located in either the north or
south sides as well.
Twenty windows were located on the south side of the house, each of them single-paned.
On the north side were twenty-one windows, each containing both primary and storm
windows. The north side of the house faces the Charles River, and windows on that side
probably contained storms because of the stronger winds blowing off the river.
Additionally, three windows on each floor were found to be older and draftier than the
others; these windows all had curved panes and were located on the north side as well.
The locations of all windows can be seen in Table 2.
While a drafty house will usually cost more to heat than a well-sealed building, an
inefficient heating system can often be just as hard on a resident's heating bill. Thus it
was necessary to examine the heating system within the house studied here. Four natural
gas-fired furnaces (Figure 4), located in a subbasement connected to the building, fueled
the central heating system in this FSILG. Each furnace was dedicated to a separate
common room, as indicated in Table 2, with individual room temperatures controlled via
manual thermostats located at the black dots in Figures 1-3.
8
Figure 1. Second floor plan showing locations of window and door retrofits. Programmable
thermostat located at black dot. Locations of heating vents shown.
ow
6"
Window
106" x 38"
IVent
I
I
i.·Single
id
Window
,'
9
_
'
~
V--I-
1
Figure 2. First floor plan showing locations of window and door retrofits. Programmable
thermostats located at black dots. Location of heating vents indicated.
|
I I tI
I I
Window
89" x 43"
Window
/89 x 43"
I I
Window
'r~el
DiningRoom
Pantry
I
0
LivingRoom
Single
I
88"x 42"
OW
- ANO31Vg
'-'
I
88'x 42"
Window
rI
-
10
door retrofits. Programmable
Figure 3. Ground floor plan showing locations of window andin ceiling panels.
located
room
social
in
thormntat located at dot. Heat vents
L lk
N
E
W
6T' x 44"
S
.75"
Double
Kitchen
Pantry
Thermostat
Zeroth Floor
Social Room
Entrance
46.75" x 96" x
11
Figure 4. Five Natural Gas-Fired Furnaces Provide Heat for Hot Water and Central Heating System
While the common rooms were all heated through the central duct system, temperatures
in the bedrooms were regulated with baseboard heaters. Control for these heaters came
in the form of a small dial which opened a valve in the hot water pipes. This valve
allowed water to circulate into the finned, heat-exchanging section of piping, shown in
Figures 5 and 6.
12
Figure 5. Electrical dial and control valve for baseboard heaters. Dial is normally mounted directly
above heater.
Figure 6. Baseboard heater with fins and enclosure under normal operation.
Z
2:
.i-·
-- ·
13
In Figure 5, it is important to note the location of the dial controlling the baseboard
heater. In every room, it was mounted directly above the heater, which causes the
baseboard units to be less effective. Because the dial is located so close to the heat
source, only the air around the heater reaches the desired temperature; air in the rest of
the room remains colder. As a result, this may be a major factor in the low levels of
human comfort experienced in many of the rooms.
Hot water for the baseboard heaters was supplied by a fifth gas-fired furnace, which
provided all hot water for cooking and bathing as well. To maintain an adequate amount
of hot water on hand at any given time, three water-heating storage tanks were located
next to the furnaces (Figure 7).
Figure 7. Three hot water storage tanks.
0
Delivery of natural gas to the furnaces at the rear of the house was made through a
pipeline coming in from the street. The pipe ran along the ceiling of the ground floor,
and a gas meter was affixed to the system in a utility closet near the front of the house.
Actual meter readings were taken by the gas company once every few months, with
estimates of monthly usage, based on historical records, being used when actual readings
were not made. During the heating months (usually mid November - mid April), gas
consumption averaged around 1300 therms per month, with some variance depending on
the outdoor temperature and wind conditions. Table Al in the appendix shows complete
historical records for January 2003 through March 2006.
Given these historical records and an understanding of the building characteristics, one
begins to get a sense of the areas where heating energy could be saved - namely, through
improving the windows, doors, insulation, and heating system of the home.
14
Retrofit
In the interest of reducing costs and minimizing installation time, it was determined that
installing plastic window sealing and caulking cord in the windows, weather stripping
and doorframe sealant on the doors, and replacing the manual thermostats with
programmable ones would be the best retrofitting options for the scope of this study.
Because they were low-cost and easy to install, these methods were deemed more likely
to be carried out by other FSILGs as well.
For the retrofits, described below, all materials were obtained from a local Home Depot,
and are specified in Table 3. Installations were made during the week of January 8-14,
2006, and remained in place until April 13, 2006. The remainder of this section specifies
the details of each retrofit applied in this study.
Table 3. Retrofit Bill of Materials
Brand
Material
Mortarlite
Frost King
4
4
$4.97
Great Stuff
Weatherstrip & caulking cord
Extra large window insulation kit
62" x 210" x 2 sheets
Expanding foam insulation
2
$6.44
Thermwell
Weather door strip (U-channel)
2
$8.96
Thermwell
Weather door strip
2
$9.49
Frost King
Foam rubber door sealant
2
$5.37
RiteTemp
7-day, 5-1-1 programmable
thermostat
4
$28.37
Quantity
Total:
Cost
$13.47
$247.76
Windows
Window retrofits consisted of installing either solely Mortarlite caulking cord, or the
caulking cord and the Frost King clear plastic window sheeting. In each case, the
caulking cord was installed in the same manner. First, it was affixed to the inside edges
of each window frame. Then, additional cord was used to fill any other existing gaps and
cracks between the windows and their frames. These actions were made to help
minimize airflow into the house from outside. For windows containing storms, it was
also necessary to minimize airflow between the room and the airspace between the
windows as well. To address this issue, caulking cord was also applied between the
upper and lower interior windows. Once each window had a sufficient amount of
caulking cord in place, the plastic sheeting was installed.
Clear plastic window sealing was installed across the eleven windows indicated in Table
4, using the Frost King window insulation kits. Included in each kit were two 66" x 210"
plastic sheets and one roll of clear plastic, double-sided mounting tape. To install the
15
sheeting, the tape was first affixed to the frame of each window, approximately 1.5" from
the edge. Then the plastic sheeting was attached to the tape, forming an airtight seal
between the window and the room. For those windows which appeared to be especially
drafty, additional layers of duct tape were applied periodically during the winter months
to maintain an airtight seal. During these installations, both the primary and storm
windows of the 89" x 66" window located in the dining room were found to be stuck
slightly open. To remedy this condition, several pieces of scrap wood were screwed into
the frame to fill in the gaps, as can be seen in Figure 8.
Figure 8. Plastic window sheeting retrofit in dining room. Caulking cord and wooden blocks are in
place at bottom to close off large gaps. Window contains curved panes and primary plus storm
windows.
With only one exception, all rooms in which the window sheeting was installed were
common rooms. The reason for this was that most residents preferred to retain the ability
to open the windows in their individual rooms as desired throughout the winter months.
16
Although the plastic sheeting was limited to the locations shown in Table 4, caulking
cord was also installed in several other windows in the house: one window in the first
floor bedroom, two windows in a third floor bedroom, and two windows in a fourth floor
bedroom. The windows in both the third and fourth floor bedrooms were of the older,
curved-glass variety as well.
Table 4. Window retrofits
Room
# Windows
Window Size (in.)
Social Room
1
56 x 36
Bedroom
2
67 x 44
2
1
89 x 43
89 x 66
3
88 x 42
2
106 x 38
GroundFloor
First Floor
Dining Room
Living Room
SecondFloor
Library
Doors
Similar to the retrofits installed on the windows, energy-saving efforts for the doors were
also focused on reducing airflow and heat transfer from outside the house. To
accomplish this task, weather door strips were installed along the bottom of each door,
along with foam rubber door sealant on the inside edges of each frame.
On the north side of the house, the back door, measuring 35.5" wide x 80" tall x 1.75"
thick, already had a weather strip in place. It was a single rubber strip attached to the
outside of the door, but it was deemed inadequate, however, because of visible light
showing between the strip and the door threshold. This strip was replaced with a more
robust, U-channel version, which fit across the entire thickness of the door. This allowed
for greater contact area with the threshold, reducing the chance of air entering from
outside. Although the door did close fairly tightly into the rest of the frame, a small
amount of airflow was discerned on the side opposite the hinges. To mitigate the flow,
adhesive foam rubber sealant was applied to that side along the entire height of the frame.
From these two steps, the door seemed to make a sufficiently airtight seal with the frame;
the only remaining problem was a small amount of airflow entering between the metal
frame and the walls around it. To remedy this issue, Great Stuff expanding foam
insulation was applied along the top and sides of the metal frame, as seen in Figure 9.
17
Figure 9. Retrofit on back door. Rubber weather strip can be seen on bottom, with Great Stuff
insulation on sides.
Whereas the back door had made a decent seal with its frame before retrofits were
installed, the front door did not. There was no pre-existing weather strip installed on the
front door, which allowed for a noticeable gap between the bottom of the door and the
threshold. Here, the first step was obviously to install a weather strip. Unfortunately, the
front door, measuring 46.75" wide x 96" high x 2" thick, was too thick to fit a U-channel
rubber strip, so the less-robust, single-strip version had to be settled for. Although this
version provided less contact area with the threshold, attaching it lower on the door
allowed a good seal to form anyway. Once the weather strip was sufficiently in place, the
seal between the door and the frame could be addressed. On the inside edge of the frame,
there was a thin strip of cloth doorframe sealant present, but it was clearly old and worn,
and in need of replacing. This sealant was then removed and replaced with the same
foam rubber sealant used for the back door, again running the entire height of the frame.
Additional sealant was attached along the top edge of the frame as well. As a result of
these installations, the door closed tightly into most of the frame, despite the fact that the
door did not hang lined up exactly with the frame. Unfortunately, while visible daylight
was eliminated, the bottom outside corner never achieved the desired level of an airtight
seal.
18
Thermostats
While the retrofits detailed previously focused on improving the building envelope, the
final retrofit installed was concerned with the heating system itself. To reduce natural
gas consumption, programmable thermostats were installed in place of the existing
manual versions. Although there was nothing wrong with the thermostats already in
place, there was an advantage to be had by replacing them with programmable
thermostats. The advantage of programmable thermostats is that they allow for varying
temperature settings depending on the time of day and day of the week. For instance,
with the manual thermostats, every common room was set at 63 °F all the time. With the
programmable thermostats, separate temperature profiles were set up for each common
room depending on the time of day and day of the week. For each temperature profile
shown in Figures 10-13, it should be noted that Monday through Thursday have been
consolidated into one category. This is because the weekday usage of each room is
consistent for those days. Fridays see the same usage as other weekdays during the day,
but due to events or social activities, usage may change at night. Similarly, Saturday and
Sunday are set for different schedules because of changes in the usage of each room on
those days. Each schedule was made in an attempt to keep rooms warm during times of
usage, but to reduce the temperature as low as possible when rooms were not being used.
To this end, 57 °F was set as the general "unoccupied room" temperature, while rooms
were transitioned up to 65 °F when they were in use.
19
Figure 10. Social room thermostat settings
A~
ti
-
O
65 - ------ --------- --------------
)
0C
0
N
------ ------------- -----------
CN
------------------------
---------------------------------
-----
63 -
---------------------------
-----------------------
0
-------- ---------------------- -----------------------------------
&. 61E
959
- ------------------------------------------------------------- -------- --------------------- ........
57 -
I
T
55
Monday-
---------
----------
·
I
Friday
Saturday
--------------------------
Sunday
Thursday
Day & Time
Figure 11. Living room thermostat settings
69
67
65
I.
63
I-
59
57
55
Monday Thursday
Saturday
Friday
Day & Time
20
Sunday
Figure 12. Dining room thermostat settings
69
67
65
LL
0
E
0
63
61
I--
59
57
55
Monday Thursday
Friday
Saturday
Sunday
Day & Time
Figure 13. Library thermostat settings
67
5E
a. 3
9j
-
za~~~~~~~~'''-'
65
0.
63 -
....
...
... ... .....
--------------- -
..........
2
ri-
CL
........
...........
.....
-- ...·---------------------
.....
- -- ---- -- -- --- --- - --- -
....
IL
I0
a.
61-
E
2
..............
. ... ...
59 -
57
......-
55
---------
Friday
I
Saturday
Thursday
Day & Time
21
--------- ----- ----
-----.........----
I
I
Monday-
... .
...............
Sunday
----
Figure 14 shows an example of one of these newly installed, programmable thermostats.
As seen previously, the locations of the thermostats are shown in Figures 1-3, each
marked by a small dot. Additionally, each thermostat controlled the heating system for
only the room in which it was located.
Figure 14. RiteTemp programmable thermostat installed in all 4 locations indicated in Figures 1-3.
22
Results
In order to determine what affect the retrofits had in reducing the building's natural gas
consumption, resulting consumption levels were compared with previous data. The
historic data containing consumption information was obtained from the gas company
(Keyspan) for the period from January 2003 through January 2006, when the installations
were made. After this point, consumption levels were determined from actual readings of
the house's gas meter. These readings could not be directly compared with the historic
data, however, due to variations in monthly and annual weather conditions.
To normalize for these variations, a record of heating degree days was obtained for each
billing cycle, and the number of therms consumed per heating degree day was calculated
for each month. In calculating this number, a baseline level of hot water consumption
needed to be established since natural gas was also consumed for water heating. Using
data for the month of July 2005, a baseline level of natural gas consumption was taken as
400 therms2 . This number was then subtracted from the consumption for each month,
with the result divided by the number of heating degree days for that period to get the
number of therms consumed per heating degree day. This was the number that was
ultimately used as the measure of consumption efficiency.
From the results, consumption efficiency was found to have improved by 32% after
installation of the retrofits. The corresponding values dropped from 1.07 therms per
heating degree day (therms/HDD) for a pre-retrofit average to 0.73 therms/HDD postretrofit. From these reductions, it was estimated that roughly $1500 was saved in natural
gas expenditures over the period of time in which the retrofits were in place3 . The
consumption efficiency and total thermal consumption are shown for all months in Figure
15 below. The vertical line indicates the point at which retrofits were installed, and the
horizontal line depicts the pre-retrofit wintertime average efficiency in therms/HDD. It
should be noted that consumption efficiency for the summer months drops off to zero
because of the baseline consumption correction factor of 400 therms for water heating.
Additionally, the four natural gas-fired boilers supplying warm air to the central heating
system were only turned on during the winter heating months, taken here to be midNovember through mid-April.
' Heating degree days (HDD) are calculated by finding the difference between the average daily
temperature and a baseline temperature, in this case taken to be 65 F. For example, if the average
temperature for the 24-hr. period of 12am-11:59pm is 50 F, then the number of heating degree days is 65 50 = 15 HDD.
1 therm = 100 ft3 of natural gas = 100,000 Btu
2
3 See Appendix for economic savings calculations
23
Figure 15. Natural Gas Consumption and Efficiency per Month
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From the graph, the cyclical nature of natural gas consumption can be seen. It is clearly
higher in the winter months than the summer, and seems to peak around February.
Wintertime consumption efficiency can be seen to fluctuate around the average level of
1.07 therms/HDD for the winters prior to the retrofit installations. For the last three
months shown, however, consumption efficiency is clearly much lower, at 0.8
therms/HDD for January, 0.74 therms/HDD during February, and 0.64 therms/HDD for
March. Altogether, these three billing cycles saw an average consumption efficiency of
0.73 therms/HDD, constituting an improvement of 32% from the pre-retrofit average.4
For the month of February 2006, efficiency was shown to improve from the level of the
month before, despite greater consumption. This observation is probably a result of the
fact that the retrofits were not completed until midway through the January billing cycle.
Finally, there is a sharp rise in consumption levels for December 2005, pulling poor
efficiency levels up with it. This spike is believed to have arisen from an as-yet
unresolved error with the utility company, and was not taken into account for the
calculation of any averages. It clearly does not follow the trends shown over the entire
three year period, and as such, was omitted from all correctional calculations as well.
4 All consumption data presented here is corrected from its original form. For original gas bill data and an
explanation of correction methods, see the Appendix.
24
Discussion
Clearly, these results show that the impact of such low-cost and easy-to-install retrofits
on reducing consumption can be significant. It can also be expected that this impact
would be even greater in older or leakier homes as well. Fortunately, most homes
throughout the rest of the country are newer, and probably possess tighter building
envelopes than the one in this study. But among the MIT FSILGs, it is estimated that the
residence here was probably in the middle of the pack in terms of overall heating
efficiency. Under this assumption, it stands to reason that many other FSILGs could see
similar reductions in energy consumption by implementing retrofit methods like the ones
here. To make a ballpark assessment of wasted heat in these buildings, one can utilize
cooling and heating load manuals such as those of the American Society of Heating,
Refrigerating, and Air-conditioning Engineers (ASHRAE). These resources provide
guidelines for calculating heat gains or losses from external load factors such as roof and
wall insulation, internal factors, such as lighting, people, and other equipment, and from
air ventilation and infiltration with the environment. Since the areas of the building
envelope that were addressed in this study were doors and windows, one can estimate the
reductions in heat loss achieved through the retrofits applied.
Using ASHRAE guidelines, the relevant equations for calculating heat loss due to
infiltration are as follows:
(1) q = 1.10 x (At) x scfm
where:
qs= sensible heating load in Btu/hr
At= inside-outside temperature difference
scfm = Q, the infiltration in cubic feet per minute
Q= infiltration in cfm through perimeter gaps
F = perimeter (total crack length) in feet
(2) Q = Px (QI )
where:
Q/ Pis calculated using ASHRAE graph
dependent on k, the perimeter leakage
coefficient, and Ap, the pressure difference
across the window or door
Source: Rudoy, et. al.
Using these equations and the relevant ASHRAE graphs in Rudoy, et. al., one can
calculate the heat loss due to infiltration through each of the windows and doors that were
retrofitted in this study. To find the difference between before and after-retrofit values,
one can simply change the appropriate coefficients to reflect the different levels of
leakiness. Once this is done, the difference in these values indicates the wasted heat that
has been saved by installing the retrofits. Applying this procedure to the installations in
this study, it is found that approximately 50 therms per month should have been saved via
the door and window retrofits. This number is probably low, however, because the crack
sizes for many of the windows in the house were larger than 3/32 inch, which is the
largest size crack for which the ASHRAE resource used here gave data for. Given that
the retrofits were installed on the largest and leakiest windows in the house, doing the
25
same thing for the rest of the windows in the house would not yield as high of a level of
energy savings per window. However, there are four times as many windows in the
house as there were windows with retrofits applied, so the level of energy savings seen
here could likely double if applied to all windows. Clearly, a reduction of only 50 therms
per month would not have resulted in the levels of consumption efficiency improvements
that have been seen in this study, though. Thus, the question remains as to how much
energy was saved by the installation and use of the programmable thermostats.
Unfortunately, the ASHRAE guidelines referenced in this study did not hold any
information for calculating potential energy savings due to lowered thermostat settings.
However, there is a wealth of information available online from both government and
industry sources. EnergyStar, the government-backed energy-efficiency program,
provides ratings for consumers about the efficiency of thermostats and other appliances
used in the home. Additionally, they provide a number of resources to help consumers
evaluate the cost-savings that their home could incur from various behavioral changes or
technology upgrades. One such resource is a programmable thermostat calculator, which
determines the life-cycle economic savings and energy reductions that can be realized
from using a programmable thermostat instead of the manual kind. The user can input
variables, like geographic location and variations to temperature settings, which the
calculator utilizes, along with built-in assumptions, to determine the potential energy
savings.
Using this calculator5 , and the usage schedules shown in Figures 10-13, the energy
savings due to installation of the programmable thermostats should have been around 280
therms per month, or almost 1400 therms for the season. These numbers are based on the
assumption, from 2004 industry data, that each degree of thermostat setback corresponds
to about 3% energy savings per heating season. Given that each thermostat was setback
by 6 °F on average, these actions should have resulted in an approximately 18% decrease
in energy consumption. In this study, the average wintertime natural gas consumption
was found to be 1369 therms per month, for which 280 therms represents a 20% savings.
Hence, it is roughly consistent with the stated assumption. Additionally, the
programmable thermostat calculator outputs projected CO2 emissions savings resulting
from lower natural gas consumption as well. For the temperature settings used in this
study, it was projected that emissions would be cut by 4500 pounds of CO 2 per year.
Clearly, if all FSILGs installed programmable thermostats, the resulting CO2 emissions
reductions would be substantial.
Now, summing the predictions for the thermostat and retrofit installations, the total
energy savings should have been around 330 therms per month. Again, using the
wintertime average consumption of 1369 therms per month, this figure represents an
expected 24% reduction in natural gas usage. Compared to the experimental results of
32% reduction, these values are reasonably close. It is expected that part of the reason
for greater reductions in the experimental results is that the ASHRAE calculations for the
doors and windows were not entirely accurate. As mentioned before, this was because
5 Programmable thermostats savings calculator, U.S. Environmental Protection Agency.
thermostats. See Table A4 in the Appendix.
http://www.energvstar.gov/index.cfm?c=therlmostats.pr
26
the windows and doors were extremely leaky to begin with. Additional discrepancies
between experimental results and theoretical calculations may derive from the process of
correcting gas bill data for months in which consumption was estimated. These
discrepancies aside, however, the expected and actual reductions are fairly close, which
leads one to expect that reductions in the range of 25%-30% could be realized in other,
comparable FSILGs if similar retrofitting measures are taken.
Conclusions and Recommendations
According to the U.S. Environmental Protection Agency, installing a programmable
thermostat is one of the most cost-effective energy saving measures available. This fact
was clearly supported by the results shown in the experiment here, and with the trend of
rising and increasingly volatile energy prices in New England, it simply does not make
sense for any residence not to have one. If there is only one energy-saving measure that
can be implemented in a home, it should be to install a programmable thermostat. At a
cost of less than $50, and with natural gas prices above $1.00 per therm, the payback
period for almost any home will be, at most, a few months. For FSILGs like the one in
this study, the money spent could be recovered in a matter of weeks. In light of this
fact, installation of a programmable thermostat is the primary energy-saving
measure recommended here to other FSILGs.
Additionally, the results of this experiment showed that reducing outside air infiltration
through leaky doors and windows can have a significant impact in reducing energy
consumption as well. While the retrofitting methods for accomplishing this task here
were somewhat labor and time-intensive, they were also very low-cost. Thus, a valuation
has to be made to determine whether the time and effort spent are worth the potential
energy savings. For other FSILGs, which stand to save a comparable amount of energy
as the building in this study, the value of those savings are approximately $375 for the
heating season.6 If cost is an issue, then, for windows and doors, applying these methods
may be the best option. However, it should be kept in mind that installation of rope caulk
and plastic window sheeting must be done every year. This feature should be contrasted
to other options, such as window weatherstripping, which is more costly, but also more
permanent.
Window weatherstrips are similar to those made for doors, and are made to improve the
seal between a window and its frame. Most commonly, they are made from foam,
rubberized plastic, or types of silicon, and they vary in price depending on quality. An
average weatherstripping product might cost around $15-$25 for 200 inches of material7.
In this study, that price would have resulted in a cost of approximately $140-$235 just for
retrofitting the windows, versus the $74 that was actually spent on the plastic sheeting
and caulking cord. Assuming the energy savings realized from the window retrofits was
$375, as calculated above, the extra cost of window weatherstripping would still be paid
back within one heating season. On top of that, the weatherstrips would not have to be
Assuming an average savings of 50 therms per month, a five month heating season, and a natural gas
price of $1.50 per therm (taken from the average over the last 3 years).
Prices from eBuildingSource.com http://www.ebuildingsource.coni/orderinfo.asp,
Price Search "S88"
6
27
replaced each year, saving additional time, effort, and money. For these reasons, it is
recommended that FSILGs install window weatherstripping, rather than plastic
window sheeting and caulking cord.
One other low-cost method for saving energy that was not implemented in this study was
the installation of attic insulation. In most buildings, attics or crawlspaces are fairly
accessible, and insulation can be put in place without too much effort. Because the
FSILG in this study already had adequate attic insulation, this step was not taken;
however, it is recommended that FSILGs without attic insulation have it installed
before taking more drastic energy saving measures.
Finally, there are other, more drastic measures that can be taken to reduce heating energy
consumption in FSILGs. Most of these are more expensive and time-consuming, and can
involve partial demolition to portions of the building. For instance, ensuring the presence
of sufficient wall insulation requires tearing down wallboard or plaster. Such actions
usually require the work to be performed by a licensed contractor, and construction
permits must be acquired from the City of Boston. Dealing with these parties,
specifically, are known to be time-consuming processes. In order to determine what
energy savings might be seen from additional insulation, it is necessary to first determine
the U-value (heat transmission coefficient) of the wall, which requires knowledge of the
construction materials and thicknesses of each wall layer. Therefore the U-value, and in
turn, the economic savings to be seen from adding insulation, will vary from one building
to another. While the energy savings to be gained from the presence of sufficient
insulation can be substantial, again, it must be weighed against the time and costs
required.
Similarly, replacing old, leaky windows could result in substantial energy savings, but
such action shares many of these same problems. In both cases, altering existing
conditions of the house may be difficult for some MIT FSILGs because of their status as
historical landmarks, and it may be necessary to understand the protections of that status
before undertaking any of the actions discussed here. One additional challenge in the
case of window replacement is that the age and make of many windows in FSILG houses
requires highly skilled and specialized labor. In the building examined here, the curved
windows were known to be very expensive to replace (on the order of several thousand
dollars apiece). Such costs, for most FSILGs, are prohibitively expensive, and
replacement of such windows may not be justified simply on the grounds of saving
energy. Thus, the value of adding wall insulation or replacing windows will vary for
every FSILG, and should be considered on a case-by-case basis. Similarly,
replacing boilers or furnaces in a heating system will result in different levels of
savings depending on the efficiency of the equipment currently in place, and must
be considered separately for each FSILG as well.
In summary, taking simple, low-cost energy saving measures in MIT FSILGs can be
done quite easily. Just by installing programmable thermostats and reducing outside air
infiltration through windows and doors, natural gas consumption per heating degree day
can be reduced by nearly 30% or more. As suggested by the results here, and based on
28
previous literature on the subject, the recommended order of actions that should be taken
to reduce energy consumption in FSILGs is as follows:
1) Install programmable thermostats and setup schedules with lower
temperatures during unoccupied and nighttime periods
2) Insulate attic or crawlspace areas between ceiling of top floor and roof
3) Install weatherstripping on windows and doors*
4) Insulate walls*
5) Replace old, leaky windows with new, tight windows*
*For each of the actions 3-5, importance should be given to the north side of each building, then to the east
and west sides, and finally to the south side.
By implementing even the first one or two of these actions, FSILGs stand to save
upwards of $500 per month on natural gas costs, and can potentially reduce their
contribution of CO 2 emissions by 4500 lbs./yr. Although this reduction might not count
towards MIT's 2015 GHG emissions goal, it is a step in the right direction, and could
provide guidance to MIT's on-campus emissions-reduction efforts. Because of the age
and condition of the houses of many MIT fraternities, sororities, and independent living
groups, they are well-positioned to take advantage of a vast economic savings potential,
while also greatly reducing their energy consumption and GHG emissions at the same
time. In doing so, FSILGs can highlight the synergies of saving money, saving energy,
and reducing environmental impact, and can help lead the way in MIT's energy initiative.
29
References
CPI inflation calculator. in U.S. Department of Labor, Bureau of Labor Statistics
[database online]. Washington, D.C., 2006 [cited May 2, 2006]. Available from
http://stats.bls.gov/cpi/ (accessed May 2, 2006).
E-building source - order pemko products online. in eBuildingSource.com [database
online]. Isleton, CA, 2006 [cited May 5, 2006 2006]. Available from
http://www.ebuildingsource.com/orderinfo.asp (accessed May 10, 2006).
Natural gas navigator: Massachusetts natural gas residential price (dollars per thousand
cubic feet). in Energy Information Administration [database online]. Washington,
D.C., 2006 [cited May 4, 2006]. Available from
http://tonto.eia.doe.gov/dnav/ng/hist/n3010ma3M.htm (accessed May 4, 2006).
Programmable thermostats savings calculator. in U.S. Environmental Protection Agency
[database online]. Washington, D. C., 2006 [cited May 7, 2006]. Available from
thermostats (accessed May
http://www.energystar.gov/index.cfm?c=thermostats.pr
7, 2006).
Wunderground.com: History for Boston, Massachusetts. in The Weather Underground,
Inc. [database online]. Ann Arbor, MI, 2006 [cited May 6, 2006]. Available from
http://www.weatherunderground.com/history/airport/KBOS/2006/5/6/DailyHistory.h
tml?reqcity=NA&req state=NA&req statename=NA (accessed April 13, 2006).
Membershipnumbers spring 2005 - FTP and IFC rosters. 2005. Cambridge, MA: MIT
Office of Fraternities, Sororities, and Independent Living Groups.
Fall 2004 FTP. 2004. Cambridge, MA: MIT Office of Fraternities, Sororities, and
Independent Living Groups.
Armstrong, Robert C., and Moniz, Ernest J., et. al. 2006. Report of the energy research
council. Cambridge, MA: Massachusetts Institute of Technology.
Battles, Stephanie J. 2001. Residential energy consumption survey. Washington, D.C.:
Energy Information Administration,
ce tables/enduse expend2001
ftp://ftp.eia.doe.gov/pub/consumption/residential/200
.pdf (accessed October 25, 2005).
Rudoy, William, et. al. 1979. Cooling and heating load calculation manual, ed. Rudoy,
William, et. al. Atlanta, GA: American Society of Heating, Refrigerating, and AirConditioning Engineers, Inc.
30
Appendix
Gas Bill Data Corrections
Like most utilities, the one providing natural gas to the house in this study did not read
actual consumption from the gas meter every month; instead, it is much more convenient
to measure once every few months, and use estimates for months where actual readings
are not taken. Over the long term, customers will be charged for exactly what they
consumed, but over the short term, they may be charged too much (or too little) if the
utility company estimates are not accurate. Unfortunately, this discrepancy made it
difficult to accurately determine true consumption and efficiency for every single month
of this study. For this reason, corrected consumption estimates were made based on the
gas bill data, and, specifically, from the data when actual readings were taken for several
consecutive months. This section will show the original gas bill data, along with the
corrected version, and explain the assumptions and extrapolations made in formulating
the corrected data. Table Al shows these data below.
In the table, the shaded boxes on the left-hand side represent consumption values from
Keyspan bills that were estimated. All other boxes indicate actual meter readings.
Because the estimated values might be higher or lower than what actually occurred, it is
these shaded rows that are corrected on the right-hand side of the table. Corrections were
made using the first month with an actual meter reading (represented by the shaded boxes
on the right-hand side). The numbers in these boxes were lowered, and the lower
numbers of therms that they represented were distributed among the preceding months
with estimated consumption. The therms were distributed in such a way that the
consumption efficiency would be equal for each month in that period. For instance, for
the billing period of February - March 2003, the estimated therms consumed were
obviously low. From the gas bill numbers, that month had a very good consumption
efficiency of 0.64 therms/HDD. The month previous had an actual reading, showing an
efficiency of 1.16 therms/HDD, and the month immediately following (March - April)
had a very poor efficiency of 2.07 therms/HDD. It seems unlikely that the physical
conditions of the house changed so drastically over those three months to result in such
variations in consumption efficiency. Knowing this, and that the gas meter shows total
running consumption, rather than monthly consumption, these data suggest that the
March - April reading was so high because it made up for the February - March estimate
being too low. To determine the corrected consumption, then, the efficiency for March April, shown in the shaded box on the right, was chosen arbitrarily. The corrected therms
consumed for March - April were back-calculated from the chosen efficiency, and the
difference between the corrected and original estimated consumption for March - April
was then added to the original estimated consumption for February - March. The result
was then used as the corrected consumption for the February - March bill. In doing this,
the actual therms consumed are effectively redistributed to their proper month of
consumption. From that corrected consumption value, the corrected therms/HDD were
then determined for February - March, and if its value was different from the arbitrarily
chosen value in March - April (in the shaded box), then the March - April value was
appropriately increased or decreased until both values were equal. This same iterative
31
process was used for each case of estimated months, where each of the chosen values that
drive the other numbers is located in a shaded box in the right-most column.
Since summertime consumption efficiency is significantly different from the wintertime
efficiency, slight alterations to this procedure were used for both April - May, 2004, and
for April - May, 2005. In these cases, the value for consumption efficiency was simply
taken from the only April - May period with an actual meter reading (in 2003) as 0.86
therms/HDD. Other than choosing the number in the shaded box, all other steps used
were the same as above.
February - March 2004 was calculated in exactly the same procedure as outlined on the
previous page.
All data for the months of January - April 2006 were taken from actual meter readings
made during the experiment, and consumption efficiency was determined in the normal
manner of subtracting 400 therms as a baseline, and dividing the result by the number of
heating degree days.
Once all of these values were calculated, the corrected wintertime average of 1.07
therms/HDD was found. This value was then used for November - December 2003,
since all of the estimated months immediately preceding it were summer months.
Additionally, the pre- and post-retrofit winter averages for consumption efficiency are
shown in the box at the bottom of the table.
32
Table Al. Original and corrected Keyspan gas bill data
-
i
irrected Therms
Corrected
insumed
Therms/HDD
.......................................
183.0 ....... ..................................
.........
1.......
...........
................. .........................
1830
1.15
1195
782
532
0.86
441
.... ............ ...................................................................
431
270
294
552
1110
.................
....................
.......................................................
0.48
1.11
10.33
-6.50
-0.83
0.38
1086
2148
1418
1364
618
327
-11.6O
284
....
. ............
..........
...............
...........
-033
0.84
i
1.02
.......................
... ......................
.
.........
. .... _ 1111
...........
1260
0.97
..
......................
.................
1654
358
............
...........................
.......
.........
1343......
0.98
14.03
1135
809
-12.33
3
.........
0.73
0.975
1542
105384
..........
78
1.13
I
.. 4
.......
... ... 01.80
J;
-%nvci oy1
.
....
I .UU ·
1175
.. .. ...........
.32
0.75
.O
919
1.07
........
...........
.......I......
.......
...................
. . ...........
............
.1-....... .1I-I...
........
.....
.... -.1........
.....- -- .....
33
Pre-retrofit winter avg:]
1.07
Post-retrofit winter avg:
% change:
0.73
32%
Economic Savings Calculations
To calculate the economic savings incurred from the retrofits, the actual therms
consumed had to be compared with the amount of therms that would have been
consumed, had the retrofits not been put into place. To find the level of consumption that
would have taken place, the pre-retrofit average consumption efficiency was used, along
with the number of heating degree days in each billing period, to back-calculate the
respective consumption. That is, the average efficiency of 1.07 therms/HDD was
multiplied by the number of heating degree days, and the baseline thermal consumption
of 400 was added to the result. Using the New England natural gas prices, as given by
the EIA at http://tonto.eia.doe.gov/dnav/ng/hist/n3010ma3M.htm, the corresponding
expenditures were found. From these values, it can be seen that the total energy savings
for the 2.5 month period in which retrofits were installed was about $1,543.96.
Additionally, the average difference between therms expected to have been consumed,
and therms that were actually consumed each month was 281.3 therms. Compared to the
theoretical prediction from the EPA Programmable Thermostat Savings Calculator of 280
therms per month, this value appears accurate.
Table A2. Economic savings calculations
Billing Period
Total Charge
Corrected
Therms/HDD
Corrected Therms
Consumed
Monthly costs incurred with retro
0.80
2,007.92
1057
/-23
16/ . ..........
..........
.-.92.......
..!.0
........
.7..
....
.....
.......................................
...........
.................................
2...,o...
..oe.....
.-....<$ .........................
............
6..2...
.....
....
................................
......
......... .......
. . ...........
....................
0.75
0.64
2/9-3/10/2006
3/10-4/10/2006
1175
832
... ........................... ............ I....................J.................. ...... .......... ..............
................-. J...-.-...--....-...-..-..--..-..--..~....-..
$
$
021 ........................
1.90
.$
.....
~.........
........
. .......................
e..2......!...
1037 $
674 $
2,115.00
1,497.60
...... ..........
..........
Cost/therm
Heating
Degree
Days
..................
................ .-...........
1.80
1.80
............. . ....................................................
Monthly costs that would have been incurred without retrofits
$...................
2,429.09
1.07
1/£-2i9A06
..
...............
..........................
...... .............
...........
................
!.....O.......
:....:2..
...... .....
..................................
.........
... ..... ...... .......... .........
. 1278
!......]
.......
.......
...................
.......
..!..:.~.6..
2/9-3/10/2006
3/10-4/10/2006
. . .....
~~~~~~~~~~~....
1.07 $
1.07 $
1510
1121
. .. ....
2,717.26
2,018.12
Money Saved:
......
......I ......
.......
eSad:.............
...............
.................
...............................
...............
...... .................
. . ... .. . .... . .................
Feb-06
$ ....................
421.17
Total:
34
Mar-06 $
602.26
Apr-06 $
$
520.52
1,543.96
$ .. . ......1.90
021
!............9........
...........
0......................
[..2... . ....
1037 $
674 $
1.80
1.80
.. .......
....... . ..........
ASHRAE Calculations
Using the equations shown on page 24, the following Excel spreadsheet was created to
determine the energy savings seen from each window and door that was retrofitted. The
variables in the columns are found based on ASHRAE graphs, and the assumptions
indicated in the table. From those variables, qloss_total, the final column in the table,
can be determined. This variable represents total heat loss, in therms per month, through
each of the windows and doors shown. The top half of the table, representing pre-retrofit
performance, shows a heat loss rate of 71.5 therms/month. The bottom half of the table
represents the post-retrofit performance, and shows a reduced heat loss of only 23.06
therms per month. The difference in these values, 48.44 therms/month, is taken as the
energy savings due to the window retrofits.
It should be noted that values are not given for the front door in the before-retrofit table,
and for both doors in the after-retrofit section, because the relevant ASHRAE graphs
show values of Q/P that are negligible in each case. For the relevant ASHRAE graphs,
refer to Rudoy, et. al.
Table A3. ASHRAE calculations for energy saved via window and door retrofits
ASHRAEcalculationsQuantity!Perimeter (ft)sCp
IDeltapk
IQ/P(from Q
(cfm)
qs
1heatloss
qlos
tot
Before Before~
~ ~ ~
i
'graph)
:'(Btu/hr) (Bu/mo.) al (therms)
0th Floor
0
ac'ii
loor
1925i
.......
0.95
0.0095
6i
0.2
3.85!
127.05
91476i
0.91
i
.............................
. ..... . ..... .. ... ............
. ..... .......................
½............
... ....................
....................
......... .. .... .. .. ..........
.
..........
....... . ............... . ..............
.....................................................................................................
Front door
1!
23.79
0.15 0.0015
6ioo in
............................
........ .-....
E
182-'601
253.--".'8'
'
Fra'e o..
.. ..............
.......
......
........
........
i........................i............;...............!.
......
...............
........................
..................
.................
... .. 854.701
.. ......
.......
..........
......................
. 615384
. ..........
. ..........
.................
.................................
..........................
BD
window
2i
1850
0.95
0.10
6i
1.4:
2590:
12.31
Game roomwindow
1
1533
0.15' 0:02
61
050
767 253.00, 182160
182
...................
. . . .- . .
Fl o
......... ......, . . ..
1stFloor . ......................
.......
i.........
' ...................
i .....
i . .....
...........
.... .................
......................
. ..
..........................................
.............
..........
...
.......J.
.. ...........
.........
.......
.....
............
... .........
~
.....
............
.......... ;
....
.........i.........
Livingroom window . .21
67.
O
015
002
6!
0.50;
1083! 357 50
257400
7.72
_
1
2.83
0.95i
010
6!
1.4i 36.17[ 1193.50'
859320i
8.59
Dningroomwindow
Dinn room window2
2
22.00
0.95i
0.10
61
14:
30.80 1016.401 7318081
14.64
.. ........
...............
...................
....... ..............
... .......... ..........................
.........
...................................
....
...........................
...........
.......................................
...... . ......
..............
........
. ....... ...................
.........
........
..............
...............
...... ... .........
..... ....................
............................
. .......................................
..................
.......
. ......................
.. ...............
.................
.........
.............
....................
...............
.
.....
........
.....
.............
.....................
.....
............
.
Flo..........
.... .....
. ......
. .................
..........
2nd~~~~~~~~1-.
oo 28.676
0.95
Library
window1
1
'"..
.........
'".;.' window
...'.'".."'.
......
........
......
........... ..........
Library
2. .... .....
2;
'.......... :'"'.. .............
.......... ..............
1.4:
1.4
10 -6
.....
I........
.........
..........................
.' ".
........
' ... 6
... ............
d~.............
24.00
0.95
0.10
.........
After
Floor
Othdloor
'Bac
Oackdoor
Front
door
BDwindow
Aft
er '
'
....
;Total:Iii
9.54
...
''.'"'
"'..........
15.97
71.50
ind. .. 15.mwh
Assumptions:v
w
delta t:.
30 deg. F
hours720/month
11
1
1
2
wind'ow'
Gamieroom
1stFloor
Livingroom window
Dining
roomwindow1
Diningroom window2
40.13 1324.401 953568
33.60 1l08.80
798336/
1
' : [ho'urs-'
'"'~
.........
72'0'/'mo'nt'l;~
......
.............
...
. i.........................
'~ ;..
1.25
19.25
2379
18.50
::....2 ............. .... .. ,~.. .........
. ... .
:.
8.33:
...... ~,
.
274.73
197802
.
.
21.671 0.15
0.021
1
0.18i
3.90
"r~~~~~~o'm'wi'ndow'i~~~.
....1.....
2".8 0.10f
.....
'.63
" ...'.'96.............:i''
......
.....
.....
'' 0.45
.......
......1163
Dining
25.83:
0.95.
1.......
0.10 i
22.00
0.95i
1
0.45i
9.90
~~~~~~~~~~~~~~~~~~~~~............i
2nd Floor
Librarywindow
1
1
~~~~~~~~~~~~.
Librarywindow2
2
'i
3.96
..........
.......
...
.2.76
............ 91.06 65577.6
...........
... ~
...........
j............
0.18,
.2
1,..... ~,.....
15.331 O1SF'__
.........
3
1
2
.j............
................
(.......
..
i
095
1 ,0.15
--0.95
0.101
0.45!
..............
2867
24.00
0.95,
. ..
0.95
.... ...... ............
0.10
0.101
1
1
............................
. ..4,}..........
........... . ..........
_____
35
_:_
_
:.
................
,
128.70
92664
2.78
'
38."..
....... '.'.".":
. '.'76
."'
."7i.
383.63o''5'1
276210:
2.76
326.70
235224!
4.70
...... .... .. .................
.......
045
0.45
_Ch'ane:
0.66
;
.
1290:
10.80
42570.
356.40
306504
256608
Total:
i'_hn
.............. .........
...........
3.07
5.13
23.06
' 46.44
U.S. EPA Programmable Thermostat Savings Calculator
The thermostat calculator was an Excel document downloaded from the EnergyStar
thermostats. The
website at http://www.energystar.gov/index.cfm?c=thermostats.pr
variables input into the calculator are shown in Figure Al. The city of Boston was
selected as the location from the drop down menu next to the arrow. A cost of $50 was
chosen to represent the unit retail price for an average programmable thermostat
(although the ones in this study were only $28, most are more expensive). The cost of
natural gas was chosen to be $1.50 per therm, which was the average residential price in
New England over the period January 2003 to January 2006. The usage patterns shown
are for the social room thermostat settings, as an example.
Figure Al. Thermostat Calculator Data Entry
In Figure A2, the output of the calculator is given. The most important values here are
line number four, the life cycle energy saved, and line number six, the life cycle air
pollution reduction. In making the calculator, the EPA assumed a fifteen-year life cycle
for each thermostat. Therefore, to find the values for a single year, (essentially just one
heating season) one only needs to divide those values by 15. For the example here, the
energy saved per heating season becomes 549/15 _ 36.6 MBtu. Using the conversion of
1 therm = 100,000 Btu, this translates into
36.6 x 106 Btu x (1 thermi 1x 105 Btu)= 366 therm. Thus, for a five-month heating season
(mid-November to mid-April), this results in a savings of 73 therms/month.
Figure A2. Summary of Benefits for Programmable Thermostat in Figure Al.
$40
Initial costdifference
Lifecycle savings
Netlife cyclesavings(lifecycle savings- additionalcost)
both Heatingand Cooling
Lifecycle energysaved(MBTU)-includes
$3,907
$3,867
549
Simplepaybackofadditionalcost(years)
Lifecycle air pollutionreduction(Ibs of C02)
0.1
20,974
(numberofcars removedfromthe roadfor a year)
Air pollutionreductionequivalence
(acresofforest)
Air pollutionreductionequivalence
Savingsas a percentof retailprice
36
2
3
7733%
Because the schedules of the other thermostats were not as reduced as the one for the
social room, they each resulted in savings slightly less than 73 therms/month. Thus, in
total, the four thermostats showed savings of just under 280 therms/month using this
calculator. A similar analysis can be performed with the estimated CO 2 savings.
Using the number in Figure A2 above of 20,974 lbs. CO2 for the life cycle, dividing by
15 will yield the annual CO2 reduction of 1,398 lbs. Again, since each of the other
thermostats saved slightly less natural gas, they each would see slightly less reductions in
CO 2, of just over 1,000 lbs. each. Thus, in total, use of the programmable thermostats
results in a reduction of about 4,500 lbs. CO 2 per year for the building in this study.
37