A Thermal Analysis of a
Small Apartment
Comp Exam
Danielle Doyle
1/31/2008
Abstract
The purpose of this paper is to explain how to conserve energy in a typical residence by conducting a
small case study in a one floor, second story apartment indicating areas that use and/or waste the most
energy, and steps to reduce that wasted energy, including small simple lifestyle changes. Temperature
data will be collected in a one-24 hour period every hour to effectively portray the areas in the
residence with the most heat loss in order to make the best decisions to conserve the most energy. The
windows, walls, electrical outlets, and baseboards all contribute to this heat loss throughout the entire
residence. The living room is the coolest area in the living space; therefore there is more heat loss
occurring here than in any other part of the residence. Doing the necessary improvement to all areas
could help lessen all of the heat loss in the residence.
Introduction
With energy costs being as high as they have ever been, there have been efforts for
improving energy use at home. Most people are not fully aware of the fact that they can
deteriorate or improve the energy performance of their entire residence (Zmeureanu and
Merceau, 1999). Zumeureanu and Merceau (1999) concluded that energy conservation
appliances can only save so much energy; however, simple lifestyle changes can drastically
improve energy conservation as well. A typical home uses more energy to heat and cool the
residence requiring more money than any other system in the residence. On average, 45% of a
utility bill goes toward heating and cooling (DOE, 2006). Unfortunately, a lot of that energy is
wasted, especially by indoor air leaks and not enough insulation, therefore, leading to large
energy saving potential (Peets et al., 2006). The purpose of this paper is to explain how to
conserve energy in a typical residence by conducting a small case study on a one floor, second
story apartment. The study will indicate areas that use and/or waste the most energy, and steps to
reduce that wasted energy, including small simple lifestyle changes. For the purpose of this
study, temperature data will be taken during a one 24-hour period during the month of January to
show areas of the residence that waste the most heat; the data will then be analyzed to show how
that heat can be conserved.
Heat Transfer
Knowing how heat is transferred is important in reducing heating costs. There are three
methods of transferring heat; conduction, convection, and radiation. In a study conducted by Oak
Ridge National Laboratory’s Building Technology Center and Tuskegee University, an energy
efficient house was built and used to study energy conservation methods. The most important
energy efficient features considered were good insulation (conduction) and airtightness
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(convection). The largest method of heat loss during the winter is by conduction. Heat can
escape by conduction through walls, ceilings and windows (Harley, 2002). Insulation is used to
stop this heat conduction. The effectiveness of insulation is based on the “R” factor, where the
higher the R-factor, the greater the effectiveness. Older houses and buildings were built when the
cost of energy was lower and the insulation was more expensive for the same R-factor.
Therefore, installing more insulation can save energy and money. Peets et al. (2006) indicated
that insulation of the building decreases energy costs and also decreases the inequality of
individual costs in apartments.
The second largest loss of heat is by convection, or air leaks. Air can come in and out of a
house in many different places: cracks around windows, cracks under doors, places where wires
or pipes come into the house, and from the electrical outlets (figure 1). By looking for cold drafts
during the winter, energy and money can be saved by stopping this air flow. Imbrahim et al.
(2004) noted that by minimizing air leakage to maintain comfort, energy is also reduced. In
addition, large sources of heat loss are through attics, fire places, and dryer vents (Tyrol, 2004).
Attic spaces are cold in the winter and there is only a thin, unsealed sheet of plywood separating
the attic from the living space, supplying cold air to flow into the living space. Adding an attic
stair cover can reduce this heat loss by providing an air seal, reducing the air leaks.
Sixty-five percent of homes in North America have a fire place, and researchers have
determined that there is significant heat loss through a fire place during the winter (Harley,
2002). Hot air rises up any exit it can find and is replaced by cooler air, therefore causing a house
to lose heat. Keeping the flue damper closed is essential because if it is not closed, warm air can
escape continuously.
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Radiation effects are minimal when referring to heat loss in a house during winter
(Harley, 2002 - pg. 132). Some heat energy will radiate away from a house on a cold night. The
lower the outside temperature, the less energy will be radiated because warmer objects emit more
radiation than colder objects. Therefore, the lower the infrared temperatures of external parts of a
house are, the less energy will be radiated away from it. The most obvious way to reduce heat by
radiation is to close curtains at night and open them during the day taking advantage of the
radiation from the sun.
Figure 1. Sources of Air Leaks in a Home. Areas that leak air into and out of a home.
1. Dropped Ceiling
5. Water and Furnace Flues
9. Window Frames
2. Recessed Light
6. All Ducts
10. Electrical Outlets
3. Attic Entrance
7. Door Frames
11. Plumbing and Utility Access
4. Sill Plates
8. Chimney Flashing
Source: DOE, 2006
Energy Audits
An approach to lower and conserve energy in a residence is to find out the areas in a
house where it loses the most energy. This can be done by conducting an energy audit of an
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entire residence which will pinpoint areas that use and/or waste the most energy while looking
for methods to decrease those energy costs (DOE, 2006; Zmeureanu and Merceau, 1999).
Energy audits can be done by the homeowner or by a professional. If a homeowner wants to do
the audit his/herself, there are several items to complete; checking for air leaks, checking
insulation levels in walls and ceilings, and inspecting heating and cooling equipment are just a
few to name.
Reducing air leaks can save energy by as much as 5% to 30% per year (DOE, 2005).
Making a list of obvious air leaks is important. Air leaks can come from places such as electrical
outlets, window frames, baseboards, attic hatches, fireplaces, and wall or window-mounted airconditioners (figure 1). Looking for gaps around pipes and wires, foundation seals, and mail slots
can decrease heat loss as well. In addition, making sure caulking and weather stripping are
applied correctly is also important. Windows are a large source of heat loss in the winter,
therefore it is important to check for air leaks and gaps near windows. In a typical house, heat
loss through windows can represent 10% to 20% of the total heat lost (DOE, 2006; Hendron,
2006). Careful window selection when building a new house or renovating an old one can make
a significant difference by helping to reduce heat loss.
Low R-Value insulation is another major source of heat loss. Older homes usually do not
meet the minimum R-value requirement. Attic insulation is necessary for a reduction of heat loss
through the attic. Checking to see if all necessary areas have insulation is important; however,
checking for the R-value of insulation in walls can only be done by a thermographic inspection.
Heating and cooling equipment needs to be inspected annually to ensure they are
performing properly. Changing filters when needed is essential, and if the equipment is over 15
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years old, considering replacing the systems is important. In addition, checking the ductwork for
dirt streaks is also important because it can lead to an indication of air leaks (DOE, 2005).
An energy audit that is done by a specialist is performed in much more detail. This is
usually done room by room and an examination of past utility bills is conducted. Most
professional energy audits perform a thermographic examination, or a blower door test. This
research paper uses a type of thermographic examination for the case study (DOE, 2005).
Thermographic exams are performed to detect heating defects and air leaks. Thermal
behaviors of buildings have been studied using different methods (Peets et al., 2006). Measuring
and understanding thermal processes is important in reducing heat loss (Peets et al., 2006;
Ibrahim et al., 2004; Demirbas, 2006). The spot radiometer is the simplest type of infrared
detecting instruments. The spot radiometer shows the temperature of a particular spot. The
auditor measures the temperature of an area and observes the differences. However, a spot
radiometer does not provide the most accurate data for a home energy audit; however, it does
provide data to determine areas of heat loss by observing temperature differences (DOE, 2005).
It is with this instrument that the case study used in this paper will be conducted.
Once a homeowner or renter determines where the most energy is being lost, a whole
house efficiency plan can be formed. This plan provides an approach to make smart choices and
home improvements that can maximize energy conservation and save money (DOE, 2005).
Conserving Energy
Energy efficient improvements can not only make a house more comfortable, they can
have long-term financial awards as well. There are several easy methods that can be done to
conserve energy starting today and there are some that are time consuming, yet each method can
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have long-term beneficial effects. These methods can help save the typical homeowner or renter
25% on their utility bill in a single year (Harley, 2002).
Checking and installing new insulation in a house is a cost-effective way to reduce
energy that is wasted. On average, 31% of heat loss is through floors, walls, and ceilings due to
poor insulation (DOE, 2005). A good insulating system includes a combination of products and
construction techniques that protect a home from outside temperatures. Adding more insulation
can increase the comfort of a home and can decrease the heating and cooling needs by up to 10%
if the insulation is installed properly (Harley, 2002). Figure 2 shows the areas that need to be
checked and the proper places where insulation should be installed in a typical home.
Figure 2. Check for Insulation. Adding insulation in the areas shown
above may be the best way to improve your home's energy efficiency.
Source: DOE, 2006
Insulation must be properly installed to work effectively. The insulation must fill the space
completely and evenly because any blank spots or corners will allow heat to escape (Harley,
2002; Hendron, 2006).
Air leaking into a house can waste energy and money. Checking for air leaks (figure 1) is
a fast and effective way to decrease the energy that is being wasted. Using expansion foam
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insulation, caulking, and weather stripping to fill the seams, cracks, and openings can save, on
average, 10% on a utility bill (DOE, 2005). In a typical residence, 21% of heat loss is through
windows and doors (DOE, 2005). Installing caulking and weather stripping on doors and
windows can substantially decrease heat loss. In addition, leaking ducts accounts for 15% of heat
loss as well. Caulking and duct taping those leaks can lead to a substantial drop in heating and
cooling costs (DOE, 2005). Using the expansion foam insulation around electrical outlets and
light switches can also decrease heat loss.
Almost half of American homes have single-pane windows (DOE, 2005). Replacing
single-pane windows with double-pane windows is an effective way to reduce heat loss in a
house. There are now on the market low emissivity windows that substantially reduce heat loss;
however, this could be expensive. There are, however, simple, less costly methods that a
homeowner or renter can do to save heat energy. Using a heavy-duty, clear, plastic wrap that is
sealed to the frame of the window can reduce air infiltration. In addition, using insulating
window shades or installing storm windows can reduce heat loss by as much as 25% to 50%
(DOE, 2005). As noted previously, closing the window shades during the night and keeping
them open during the day is a simple method to conserve energy.
During the winter, thermostats should not exceed 22.2°C (72°F) during the day and
18.3°C (65°F) during the night. A thermostat should be as low as comfortable in the winter.
Every 0.56°C (1°F) that the thermostat is lowered saves an average of 3% on the heating costs
(DOE, 2005). In addition, lowering the temperature on the thermostat even more when people
are not home can save even more energy. If a house has radiators and baseboards, a homeowner
or renter should avoid placing furniture or other objects in front of them blocking the heat.
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Water heating bills, on average, account for 13% of the total utility bill. However, using
less hot water, turning down the thermostat on a water heater, insulating a water heater, or
buying an energy efficient water heater can reduce a water heating bill. A comfortable
temperature for most people on their water heaters is 48.89°C (120°F). Most water heaters come
with a factory temperature that is over 48.89°C (120°F); therefore, if the temperature is
decreased it will maintain comfort and cut energy costs.
There are also simple techniques that can improve overall heat conservation in a
residence. Listed below are just a few methods anyone can do to conserve energy in their
residence:

Set ceiling fans to blow towards the ceiling to circulate the warm air that has risen to the
rest of the room.

Wash only full loads of dishes in the dishwasher.

Allow dishes to dry naturally instead of using the dry-cycle in the dishwasher.

Take shorter showers instead of baths.

Wash clothes in cold water if possible.

Use compact florescent light bulbs instead of incandescent lights.
There are many more simple techniques that can be used to save energy in a typical residence,
these are just a few to mention. Utilizing these techniques can save energy and money on a utility
bill.
Case Study: A One Story Apartment in Carlisle, PA
A small one story, second floor apartment in Carlisle, PA will be used to illustrate a
technique to determine which areas of the residence are losing the most heat using a Kestrel and
an Infrared Thermometer. The purpose of this study is to show where to collect appropriate
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temperature data in a one-24 hour period that will effectively portray the areas in the residence
with the most heat loss in order to make the best decisions to conserve the most energy. In
addition, the study will include several possible techniques to reduce heat loss in the residence.
The study area is a five room apartment, with a small bathroom and laundry room.
Figure 3 shows the layout of the apartment, including sources of typical heat losses and heat
gains as explained above. The average temperature in January for Carlisle, PA is -2.56°C
(27.4°F); therefore, it is important for residents of this area to conserve energy and reduce heat
loss.
It is expected that areas around the windows lose the most due to the fact that the
windows are not well insulated and areas with air leaks also lose heat.
Methods
The layout of the residence was drawn and digitized, and then analyzed to determine the
best methods to collecting the data. After analyzing the layout, the residence was split up into
blocks to receive a more through temperature reading of the residence (figure 3). The larger
rooms are split into three blocks, while the smaller areas are split into only two blocks. Each area
is marked with a number, one through twenty, in order to best illustrate the areas without any
confusion. Temperature data was collected every hour during the 24 hour period beginning
midnight on January 10, and ending ll:00 p.m. on January 10, 2008. The temperatures were
collected at eye-level in the middle of the blocks to keep consistency, and areas that typically
lose heat were measured using the infrared thermometer in order to observe the temperature
differences. The dryer vent, electrical outlets, light switches, baseboards, windows, and walls
were all measured using the infrared thermometer. In addition, the door to enter the residence
9
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was measured using the infrared thermometer as well. The television set was observed as well to
see if it is giving off any kind of heat.
A kestrel is a pocket weather meter that will be used to collect the room temperature. An
infrared thermometer measures the temperature that is emitted from an object. In addition, all
room thermometers will be kept at the same, constant temperature to ensure the data are not
misrepresented. For this particular study, the heat was turned completely off due to unseasonable
weather; however, there is no misrepresentation in the data that would be inaccurate due to heat
coming from the heating elements located in the residence. In addition, outside temperature was
collected using the National Weather Service Website; opening the door might have led to
inaccurate temperature data recordings inside the residence.
Analysis
There is considerable heat loss that is occurring at this residence. Figure 4 shows the
residence base map with overlaying average temperatures of each area to better portray the areas
of the residence that are the coolest. The windows, walls, electrical outlets, and baseboards all
contribute to this heat loss throughout the entire residence. The residence is losing heat by
convection through the walls. Figure 5 shows all of the heat sinks in area 1 and shows that there
is heat loss through all of the heat sinks in the area. All of the sinks have a lower temperature
than the air temperature. This is shown in all other areas of the residence as well. Table 1 shows
the hourly outside temperature.
Table 1. Outside Temperatures
Hours
Temps.(°C)
Hours
Temps.(°C)
0:00
1:00
2:00
3:00
4:00
5:00
6:00
7:00
8:00
9:00
10:00
11:00
6.11
4.44
3.89
2.78
1.67
1.11
0.056
0
-1.67
-0.56
2.78
5.56
12:00
13:00
14:00
15:00
16:00
17:00
18:00
19:00
20:00
21:00
22:00
23:00
7.78
6.67
8.33
8.33
7.78
7.78
7.22
6.67
6.67
6.67
6.67
7.22
11
12
20
19.5
18.6
19.2
18.7
18.4
Temperature (°C)
15.2
15
10
Temp.
(°C)
5
0
Average
Temp.
Window
Baseboard
Electrical
Outlet
Exterior Wall Interior Walls
Figure 5. Heat is being lost through all Heat Sinks in Area 1.
Figure 6 shows the infrared temperature differences between the exterior walls and the
interior walls. Comparing all areas that have exterior and interior walls, the infrared temperatures
of all exterior walls are lower than all of the interior walls.
25
15
Exterior
Interior
10
5
19
14
13
12
11
10
9
8
6
5
4
0
1
Temperature (°C)
20
Areas
Figure 6. Exterior Walls vs. Interior Walls. Exterior walls lose more heat than interior walls.
13
Heat is being lost through the exterior walls most likely due to poor insulation. There is no
particular wall that is much warmer or cooler than the other; therefore, all areas are losing about
the same amount of heat through the walls.
There are several areas where heat is being lost even more so than other areas. Looking at
the averaged hourly temperatures for each room (figure 7), the stairs are the coolest; however,
heat rises, leading to the assumption that the stairs are cooler than any other area at all times
during the winter. The living room is the coolest area in the living space; therefore there is more
heat loss occurring here than in any other part of the residence.
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Temperatures (°C)
22
21
Stairs
Living Room
20
Dinning Room
Kitchen
19
Laundry Room
Bathroom
18
Bedroom
Computer Room
23:00
22:00
21:00
20:00
19:00
18:00
17:00
16:00
15:00
14:00
13:00
12:00
11:00
10:00
9:00
8:00
7:00
6:00
5:00
4:00
3:00
2:00
1:00
0:00
17
Hours
Figure 7. Averaged Hourly Temperatures for Different Rooms
The sharp drops in temperatures, shown in figure 7, are due to decreasing outside
temperatures. The temperature at the beginning of the study was 6.11°C, temperatures during the
drop averaged 0.1°C, leading to decreasing temperatures inside the residence.
Area 19 shows the coolest place in the residence; however, area 19 is at the bottom of the
stairs and is not considered part of the living space. Referring to figure 4, area 14, followed by
14
area 15 is the coolest areas out of all of the living space. In addition, the laundry room is losing
heat as well because that area is cooler than other areas as well; therefore, there is a heat sink in
that area. The average infrared temperature for the dryer vent is 18.5°C and is the factor of heat
loss in that area. However, area 14 is the coolest area of the residence; therefore, there are several
sources of heat sinks in that area.
Air leaks around window frames can account for 10% to 20% of total heat loss.
Comparing all four windows in the residence, the window in area 14 shows the lowest infrared
temperature (13.7°C) of all windows (table 2). Area 14 is almost 2°C cooler than the window in
area 4. This shows that there is heat loss through the window in area 14 which accounts for the
low temperature of only 19°C. The average temperatures of all other areas with windows are
either 19.5°C or 19.4°C.
Table 2. Average Infrared Temperature of Windows
Areas with Window
1
4
13
Average Infrared Temperature (°C)
15.2
15.9
14.5
14
13.7
In addition to the windows, area 14 has the coolest infrared temperature for all of the
electrical outlets (table 3). Air can leak through electrical outlets attributing to heat loss and the
outlet in area 14 is substantially cooler than all other outlets.
Table 3. Average Infrared Temperatures of Electrical Outlets
Areas
Average Temps. (°C)
1
18.4
4
19.7
6
20.8
7
23.2
9
20.5
11
20.6
12
18.7
14
17.8
The baseboards in the residence had an average infrared temperature of 18.8°C and most
areas were relatively the same (table 4); therefore, the baseboard in area 14 did not contribute to
major heat loss as did some of the other heat sinks.
15
16
21.7
Table 4. Average Infrared Temperatures of Baseboards
Areas
1
2
13
4
Average Temps (°C)
18.6
19.4
18.6
18.6
Discussion
Conducting a thermal analysis of a residence is a good way to see where heat is being lost
the most. Collecting the temperatures of this particular residence was a good example of how a
homeowner or renter could perform a thermal analysis. The study showed the areas that lose the
most heat and the particular heat sinks that cause the most heat loss.
All areas of the residence are losing heat through the walls, electrical outlets, windows,
and baseboards, and area 9 is losing heat through the dryer vent. The windows were the sources
of most of the heat loss. Installing new double-pane could substantially reduce this heat loss,
however this could become costly. There are other simple ways to decrease heat loss through
windows. Heat loss could be lessened by using a heavy-duty, clear, plastic wrap that is sealed to
the frame of the window, therefore, reducing the air infiltration that is causing the heat loss.
Installing caulking and weather stripping windows can substantially decrease heat loss as well. In
addition, using insulating window shades or installing storm windows can reduce heat loss by as
much as 25% to 50% (DOE, 2005). Even though it is not part of the living area, heat is still being
lost in that area. Adding caulking to the frame, weather stripping the door, or adding insulation
can all help reduce this heat loss.
The walls were another source of heat loss. Installing more insulation can save reduce
heat loss; however, in this particular residence, adding more insulation may not be an option
because the residents do not own the property. However, adding more insulation behind the
electrical outlets and dryer vent can save the residents energy and money because heat is being
lost through those sources as well. Using expansion foam insulation, caulking, and weather
16
stripping to fill the seams, cracks, and openings in the electrical outlets and dryer vents can also
help reduce heat loss.
Area 14 is the room to work on first for this particular residence. Heat is being lost the
most in this area because of the window and electrical outlet. Using a weather strip and adding
more insulation to the electrical outlet would be a good stepping stone to begin saving heat in
this residence. Even adding caulking to the frame of the baseboard can save heat as well. Doing
the necessary improvement to all areas could help lessen all of the heat loss in the residence.
There are other methods of reducing heat loss in this residence as well. For Example,
wash only full loads of dishes in the dishwasher, allow dishes to dry naturally instead of using
the dry-cycle in the dishwasher, wash clothes in cold water if possible, and use compact
florescent light bulbs instead of incandescent lights.
The television in this residence acted as a small heat source having an average
temperature of 36.6°C, while the average room temperature of the area that it is in is only
19.4°C. This could have added some heat to the area; however, using a power strip to plug in
appliances that produce such heat can save energy by turning off the power strip when not in use
because if not, the appliances are still using energy, therefore wasting it.
Conclusion
There is large energy saving potentials for homes and apartments in the U.S. An approach
to lower and conserve energy in a residence is to find out the areas in a house where it loses the
most energy. This can be done by conducting an energy audit of an entire residence which will
pinpoint areas that use and/or waste the most energy while looking for methods to decrease those
energy costs. A small one story, second floor apartment in Carlisle, PA was used to illustrate a
technique to determine which areas of the residence are losing the most heat using and methods
17
in reducing this heat loss. The windows, walls, electrical outlets, and baseboards all contribute to
this heat loss throughout the entire residence. Area 14 is the coolest part of the house because of
the poor insulation around the windows and electrical outlet. However, there are many
techniques that can cut back on this heat loss. Using a heavy-duty, clear, plastic wrap that is
sealed to the frame of the window, installing more insulation, and using expansion foam
insulation, caulking, and weather stripping to fill the seams, cracks, and openings in the electrical
outlets and dryer vents can all reduce heat loss. Doing the necessary improvement to all areas
could help lessen all of the heat loss in the residence.
Sources
Department of Energy, 2006. Energy Savers: Tips on Saving Money and Energy at Home. Office
of Energy Efficiency and Renewable Energy. Washington, D.C.
Department of Energy, 2005. Thermographic Inspections. Office of Energy Efficiency and
Renewable Energy, Washington, D.C.
<http://www.eere.energy.gov/consumer/your_home/energy_audits>. Accessed
January 2008.
Department of Energy, 2005. Saving Energy in Your Apartment. Office of Energy Efficiency
and Renewable Energy, Washington, D.C.
<http://www.eere.energy.gov/consumer/your_home/apartments>. Accessed
January 2008.
Department of Energy, 2005. Home Energy Audits. Office of Energy Efficiency and Renewable
Energy, Washington, D.C.
<http://www.eere.energy.gov/consumer/your_home/energy_audits>. Accessed
January 2008.
Demirbas, M.F., 2006. Thermal Energy Storage and Phase Change Materials: An Overview.
Energy Sources, Part B (1): 85-95.
Harley, B., 2002. Insulate and Weatherize: Expert Advice From Start to Finish. Newtown,
Connecticut: The Taunton Press.
18
Hendron, R., G. Barker, E. Hancock, and P. Reeves, 2006. An Evaluation of Affordable
Prototype Houses at Two Levels of Energy Efficiency. American Society of Heating,
Refrigerating, and Air-Conditioning Engineers 112(2): 296-307.
Ibrahim, E.A., H. Aglan, M. Khan, M. Bhuyan, R. Wendt, and S. Livengood, 2004. Thermal
Performance Characteristics of an Energy Efficient, Healthy House. American Society of
Heating, Refrigerating, and Air-Conditioning Engineers 110(1): 432-442.
National Weather Service, 2008. < http://nws.noaa.gov/>
Peets, S., T. Peets., E. Kokin, 2006. Modeling of Thermal Processes in Apartment Houses.
Estonian Academy of Science Engineering 12(1): 59-71.
Tyrol, M., 2004. Reduce Your Heating Bills this Winter- Overlooked Sources of Heat Loss in
the Home. Battic Door Energy Conservation. <http://www.batticdoor.com/>. Accessed
January 2008.
Zmeureanu, R. and M. Merceau, 1999. Evaluating Energy Impact of People’s Behavior in a
House: Case Study. Journal of Architectural Engineering 5(3): 99-102.
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