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University of Victoria Faculty of Engineering
Spring 2012 Technical Report
Analysis of the Financial Feasibility of Residential
Window Replacement
Megan Audley
V00230722
Mechanical Engineering
April 20, 2012
In partial fulfillment of the requirements of the
Bachelor of Engineering Degree
Megan Audley
1699 Stuart Park Terr
Victoria, BC, V8L 4N4
Co-op Coordinator
Faculty of Engineering
University of Victoria
P.O. Box 1700
Victoria, British Columbia, V8W 2Y2
Dear Ms. Khurana
Please accept the enclosed report entitled “Analysis of the Financial Feasibility of Residential
Window Replacement” to fulfill the requirements of the Engineering 446 technical report, and
in partial fulfillment of the Bachelor of Engineering program requirements.
This report does not contain any confidential or proprietary data or information.
Sincerely,
Megan Audley
Mechanical Engineering 4B
Enclosure: ENGR446 Technical Report.
i
Table of Contents
Table of Figures ................................................................................................................................ii
Table of Tables .................................................................................................................................ii
Summary ......................................................................................................................................... iii
Glossary ........................................................................................................................................... iv
1.0 Introduction .............................................................................................................................. 1
2.0 Approach ................................................................................................................................... 2
2.1 U-Factor ................................................................................................................................. 2
2.1.1 Effect of Wind Direction on U-Factor ............................................................................ 3
2.2 Solar Heat Gain Co-efficient .................................................................................................. 3
2.3 Irradiance .............................................................................................................................. 3
2.4 Window 6.3 – Thermal Analysis Program ............................................................................. 3
3.0 Analysis ..................................................................................................................................... 6
3.1 Garden Window Fenestration Area ...................................................................................... 7
3.2 Wind Measurement Correction ............................................................................................ 8
3.3 Heat Loss Calculation ............................................................................................................ 9
3.4 Financial Analysis................................................................................................................... 9
4.0 Conclusions ............................................................................................................................. 10
5.0 Recommendations .................................................................................................................. 11
Appendix A – Window Data .......................................................................................................... 13
Appendix B – Heat Loss Results .................................................................................................... 14
Appendix C – Average Monthly Weather Data ............................................................................. 16
Appendix D – Financial Data ......................................................................................................... 17
ii
Table of Figures
Figure 1 - Residence used in the feasibility study ........................................................................... 1
Figure 2 - Window view in Window 6.3 with frame properties selected ....................................... 4
Figure 3 - Window view in Window 6.3 with glazing properties selected ..................................... 5
Figure 4 - Environmental Conditions view in Window 6.3 ............................................................. 5
Figure 5 - Gas view in Window 6.3 ................................................................................................. 6
Figure 6 - Garden window on the west facing side of the building ................................................ 7
Table of Tables
Table 1 - Corrected local wind speeds ............................................................................................ 8
Table 2 - Annual heating costs resulting from window heat loss ................................................. 10
Table 3 - Window dimensions, directions, and types ................................................................... 13
Table 4 - Generic U-Factor and SHGC values for existing windows according to NFRC standards
....................................................................................................................................................... 13
Table 5 - U-Factor and SHGC values for Low-E 272 Argon filled according to manufacturer
specifications ................................................................................................................................ 13
Table 6 - Energy flow through existing windows .......................................................................... 14
Table 7 - Energy flow through Low-E Argon filled windows ......................................................... 15
Table 8 - Local monthly temperature, wind, and irradiance conditions ...................................... 16
Table 9 - Inflation adjusted annual savings .................................................................................. 17
Table 10 - Low-E Argon filled replacement window costs ............................................................ 18
iii
Summary
This report evaluated the efficiency increases and financial feasibility of replacing the windows
in a single-family residence built in 1985, located in the Dean Park area of North Saanich, BC.
The existing windows were determined to be inefficient by today’s standards, with standard
glass, air filling the gap between the panes of glass, and a solid aluminum frame with no
thermal break. The replacement vinyl framed windows meet current Energy Star requirements,
with an overall U-Factor of less than 1.82 W/m2-°C, a considerable improvement over the
existing windows.
The reduction in heat loss through the windows was evaluated by first identifying the insulation
properties of the existing windows using a program called Window 6.3, commonly used in
industry for window design. The heat loss was then calculated in Excel, and found to be 509W
for the existing windows and 289W for the replacement windows. When considering the local
cost of power, and accounting for an annual cost increase of 3% per year, it was found that it
would take 26 years to recover the initial investment of $10,734.08 to replace the windows.
iv
Glossary
Canadian Standards Associations (CSA) – Not-for-profit organization with the aim of
developing standards for a wide variety of specializations and industries.
Emissivity – The ability of a surface to emit energy through radiation.
Fenestration – An opening in a structure; can refer to windows, doors, or vents.
Horizontal Slider (HS) – A window with one portion that can be slide horizontally in
order to increase the ventilation area.
National Fenestration Rating Council (NFRC) – An organization that administers to the
rating and labeling of energy performance of windows, doors, and skylights.
Projecting Awning – Dual (PAD) – A window where apportion of the window pane opens
by angling out from the frame, creating an opening at the bottom of the opening
portion.
Projecting Awning –Single (PAS) – A window where the entire window pane opens by
angling out from the frame, creating an opening at the bottom of the window.
Projecting Awning – Dual (PAD) – A window where apportion of the window pane opens
by angling out from the frame, creating an opening at the bottom of the opening
portion.
Skylight (SL) – A window typically installed in the roof of a building to allow enhance
lighting; these windows are typically characterized at an angle of 20°, which also makes
them the least efficient window type.
Solar Heat Gain Coefficient (SHGC) – The fraction of solar radiation that enters through a
window; the lower the number, the less solar radiation enters.
1
1.0 Introduction
The feasibility analysis is performed on a single family residential building in the Dean Park area
of North Saanich, BC (see Figure 1). The building was constructed in 1985, and has not
undergone any significant renovations since. The current owner is in the process of upgrading
the building’s insulation, and wanted to determine the potential payback of replacing the
windows with a higher quality, low-e version.
Figure 1 - Residence used in the feasibility study
The properties of the existing windows are difficult to determine, as no product identification
or labelling was on the windows, and physically determining properties such as emissivity and
gas content requires equipment worth thousands of dollars. Instead, the properties were
determined using careful inspection of the windows and research of window standards from
1985. It was found that the existing dual pane windows are made from standard glass with a
fairly high emissivity rating, with air filling the space between the panes. The frames of the
windows are made from aluminum, with no thermal break between in the inside and outside.
2
The replacement windows would be dual paned with low-e coated glass, and an argon gas
mixture between the panes. The frames are made from vinyl, which has a higher insulation
value than thermally broken aluminum frames.
Replacing windows is often mentioned as an effective way to reduce heating bills; however, as
the return time can be quite long, it is often more effective to wait until the replacement is
required for maintenance of the building [1]. This report compares the heat savings to the
initial investment cost of replacing the windows, to determine how long it will take to regain
that investment.
The analysis will compare the heat loss with the existing and replacement windows, and then
determine with amount and cost of heating required to negate that heat loss. The cost savings
will then be compared to the cost of purchasing and installing the new windows in order to
determine the amount of time to repay the investment. If the payback time is reasonable (less
than 15 years), upgrading may be considered.
2.0 Approach
In order to determine the heat loss through the windows of the building, the properties of the
windows and the local environmental conditions of the building must be determined. In order
to evaluate the existing window properties, a government approved program called Window
6.3 is used, which contains data on industry standard glazes, frames, and gas mixtures to ensure
that insulation values are accurate and simpler to obtain. Local conditions were obtained from
local weather station data and solar studies, corrected for the conditions specific to the
building.
2.1 U-Factor
U-Factor, also referred to as U-Value, is an industry standard value used to describe insulating
properties, typically of windows. With units of W/m2°C, the U-Factor characterizes the total
energy flow through the fenestration, including conduction, convection, and radiation heat
transfer for a given set of environmental conditions [2]. The CSA and NFRC set specific values
for the wind speed and interior and exterior temperatures when determining the U-Factor, and
3
so these values must also be used when determining the U-Factors for the windows currently
installed in the residence.
2.1.1 Effect of Wind Direction on U-Factor
In the Window 6.3 program used for the analysis, there is an option under Environmental
Conditions that allows the user to select whether the window in question is windward or
leeward. Several U-Factor and SHGC values were calculated while varying this option, but it was
found that the was not discernible effect on the values calculated; as there was no effect, the
worst case scenario, windward, was used for all U-Factor calculations.
2.2 Solar Heat Gain Co-efficient
Solar heat gain is the amount of solar radiation that can enter through a window by either
passing directly through the glass, or through energy absorbed into the glass and frame and
then radiated into the interior of the building. The solar heat gain coefficient (SHGC) is
represented as a number between 0 and 1, where a lower value represents lower heat gain [3].
2.3 Irradiance
Irradiance is a measure of the solar radiation that hits a window, transferring heat to the inside
of the building, and, for a horizontal window, is a combination of direct irradiance, diffuse
irradiance, and irradiance reflected from the ground [4]. Irradiance is at its maximum on the
southern side of a building, which receives the most exposure to the sun. For the building in this
analysis, the southern side has the highest irradiance values and the west and east sides of the
building have lower values. Irradiance has been disregarded on the north side of the building,
as it is well shaded and so receives very little sun. The monthly irradiance values can be found
with the weather data in Table 8.
2.4 Window 6.3 – Thermal Analysis Program
Window 6.3 is a program used by industry designers to evaluate the insulation properties of a
window without having to perform expensive lab testing. The program can also be used in
conjunction with other design programs in order to create the exact frame and features
4
required [2]. There are also several standard frame types and other properties included with
the program.
When Window 6.3 is first opened, the Window view is the first page to appear. On this page,
the general properties of the window, such as window type, environmental conditions, and
evaluation properties can be selected. The insulation calculations can also be completed and
viewed on this page. If a section of the window frame is selected in the preview window, the
frame type can also be modified (see Figure 2).
Figure 2 - Window view in Window 6.3 with frame properties selected
If a pane of glass is selected in the preview in Window view, the glazing type can be selected,
and the properties such as number of layers of glass, the SHGC, and the U-Factor specific to the
glass can be viewed (see Figure 3). In order to see a complete list of glazing types, the small
button next to the drop down menu can be selected.
5
Figure 3 - Window view in Window 6.3 with glazing properties selected
In order to customize the calculated insulation values to the specific location of interest, the
Environmental Conditions Library can be opened. In this view, a new type can be created and
customized by entering interior and exterior temperatures, average wind speed, direction of
wind relative to window, and irradiation (see Figure 4).
Figure 4 - Environmental Conditions view in Window 6.3
6
Finally, the physical properties of the frame, glazing, glass, gas fill, spacers, and blinds or
curtains can be selected and customized in their respective libraries. All views are very similar
to the Gas Library in Figure 5, where standard industry gas mixes are included with the
program, or a new gas type can be created and all relevent properties entered.
Figure 5 - Gas view in Window 6.3
3.0 Analysis
Analysis of the heat loss through the windows of the house was completed using several
different tools. The properties of the existing windows were determined by inspection,
measurement, and research of the company and window standards of 1985, as there were no
labels available to identify the brand or properties. This is a common problem for contractors
who need to evaluate the quality of unknown windows, and the only other way to determine
the properties is by using specialized equipment which can cost thousands of dollars.
The windows were determined to be made from standard clear glass with an air fill; the frames
of the windows were aluminum with no thermal break to reduce heat flow. These properties,
along with the window types, were entered into Window 6.3 in order to generate the U-Factor
and SHGC values required for the heat flow calculations.
7
The insulation values were then entered into Excel in order to complete the heat loss and
financial calculations.
3.1 Garden Window Fenestration Area
One window that was more difficult to calculate was the pop-out garden window on the west-
facing side of the residence. The pop-out consists of window panes on 3 sides and the top, as
seen in Figure 6. Many aspects of this window are different, and its properties are not readily
available, as the windows are often custom made for each situation. It was determined that the
window would be modelled as an awning type, with all of the surface area modelled as one flat
window [5] as in Equation 1.
( )( ) ( )( ) ( )( )
Equation 1
Figure 6 - Garden window on the west facing side of the building
For the replacement window, in order to reduce costs and further increase efficiency, it was
suggested that the original garden window be left in, and a horizontal slider installed on the
inside.
8
3.2 Wind Measurement Correction
In order to calculate the U-Factors accurately, a precise measurement of the wind speed at the
windows is important. Values for the average monthly wind speed are available from the
Victoria International Airport Weather Station, which measures the speed using a standard type
U2A anemometer mounted 10m above the ground [6]. The typical window height in the
residential building is 2m, and as wind speed reduces logarithmically as height decreases,
Equation 2 is used to correct the measured values.
( )
Equation 2
Where ux = Wind speed at height zx (m/s)
ur = Wind speed at height zr (m/s)
zx = Desired height of the measurement (m)
zr = Reference height (m)
α = Atmospheric stability coefficient = 1/7
This results in a wind speed reduction of approximately 20% from the values measured at the
weather station. The original and corrected values can be seen in Table 1 below.
Table 1 - Corrected local wind speeds
Mean Wind Speed
(m/s)
Corrected Wind Speed
(m/s)
January 2.64 2.10
February 2.72 2.16
March 2.69 2.14
April 2.64 2.10
May 2.56 2.03
June 2.42 1.92
July 2.22 1.77
August 2.06 1.63
September 1.94 1.54
October 2.14 1.70
November 2.69 2.14
December 2.81 2.23
9
3.3 Heat Loss Calculation
The heat loss through the windows is calculated as a sum of the temperature driven heat loss
due to conduction, convection and radiation due to the temperature difference between the
interior and exterior of the building, and the heat gain due to the solar radiation on the
windows and can be seen below in Equation 3. The heat flow equation assumes that the
humidity levels are the same in the interior and exterior of the building, and that there is no air
infiltration due to openings or leaks in the window [3].
( ) ( )
Equation 3
Where q = energy flow (W)
Uf = U-factor (W/m2*K)
Tout = Outside air temperature (°C)
Tin = Inside air temperature (°C)
SHGC = Solar heat gain coefficient
Apf = Area of the windows (m2)
Et = Total irradiance (W/m2)
This heat flow equation was used to calculate the energy flow through the windows of the
building with the existing and replacement windows, using both standard NFRC U-Factor and
SHGC values. The results of these calculations can be found in Table 6 and Table 7 of Appendix
B. A negative value in the tables indicates a net flow of heat out of the building, while a positive
number indicates a flow of heat into the building.
The total heat loss is found by summing the loss from each window. The original windows have
an average heat loss of 509W, while the upgraded windows would have a heat loss of 289W, a
reduction of around 40%.
3.4 Financial Analysis
By finding the sum of the average annual heat loss, the annual power consumption (in kWh)
related to the windows can calculated by multiplying the heat loss by 8765, the number of
hours in a year.
10
BC Hydro, the power provider for the residence, has a two tier pricing system for residential
power. Below 1,350 kWh per month, the rate is 6.80 cents per kWh, and above 1,350 kWh it is
10.19 cents per kWh. The total power consumption of the building averages just above the
second tier threshold, so it is possible that replacing the windows and upgrading other
insulation in the house could result in a lower tier pricing for most or all of the year. For the
purposes of this analysis, the best case scenario is considered where the total power
consumption is charged at tier 2 before the replacement and at the lower tier 1 price after the
replacement. The annual power consumption and costs can be seen in Table 2, with a total
maximum annual savings of $282.34.
Table 2 - Annual heating costs resulting from window heat loss
Total Heat Loss (kW)
Total Yearly Power Consumption
(kWh)
Yearly Cost (6.80 cents per
kWh)
Yearly Cost (10.19 cents per
kWh)
Clear Glass Air Filled 0.5089 4461 - $454.56
Low-E Argon Filled 0.2890 2533 $172.22 $258.08
With a simple calculation assuming no increases to the price of power over time, it can be seen
that the payback period would be just over 38 years. The results of a more realistic calculation
which assumes the price will increase with inflation, at 3% per year, can be found in Table 9 in
Appendix D. Even with the potential savings increasing over time, it would still take almost 26
years to pay back the initial investment of $10,734.08 to replace the windows (see Table 10).
4.0 Conclusions
It was found that the replacing the existing windows, which were installed in 1985, with new
low-e, argon filled windows which has a much higher insulation value, will reduce the heat loss
from the build from 509W to 289W, a reduction of over 40%. This reduction results in an annual
savings of $282 per year, which would increase over time as power rates increase. Additional
savings may also be found in the air flow through the newer windows, and through a reduction
in cooling required during the summer due to a lower SHGC value. The quoted cost of replacing
all of the windows in the residence comes to $10,734, including installation and applicable
11
taxes. Assuming an annual increase of 3% to the cost of power, it will take 26 years to pay back
the initial investment.
5.0 Recommendations
With a potential payback period of 26 years, the time to recover the initial investment of is
quite a bit longer than other renovations designed to increase the energy efficiency of a home,
such as adding attic insulation or installing programmable thermostats. This is because of both
the moderate reduction in heat loss and the high initial investment of replacing the windows.
The expected lifespan of the replacement windows is around 30 years, so if the total savings are
recovered in the projected 26 years there will be only another 4 years to gather additional
savings before they must be replaced again.
As the payback period is much longer than the 15 year maximum desired by the client, and as
there is a limited time to accrue cost savings beyond recovering the initial investment, it would
not be prudent to replace the windows at this time. However, as the existing windows are
currently almost 27 years old, they will need replacing within the next few years. At that time,
replacement of the windows can be considered a maintenance cost, and the energy savings
compared against the cost of upgrading those windows to a more energy efficient version.
12
Works Cited
[1] BC Hydro, "Get Energy-Efficient Windows," 11 February 2012. [Online]. Available:
http://www.bchydro.com/guides_tips/green-your-
home/heating_guide/energy_efficient_windows.html. [Accessed 15 April 2012].
[2] Lawrence Berkeley National Laboratory, "Window 6.3: Documentation," December 2011.
[Online]. Available: http://windows.lbl.gov/software/window/6/w6_docs.htm. [Accessed
15 April 2012].
[3] NFRC, "Fenestration Heat Transfer Basics," in NFRC Simulation Manual, 2006, pp. 3-1 to 3-
13.
[4] Natural Resources Canada, "Photovoltaic potential and solar resource maps of Canada," 12
December 2011. [Online]. Available:
https://glfc.cfsnet.nfis.org/mapserver/pv/index.php?lang=e&m=d. [Accessed 10 April
2012].
[5] J.-W. Engineer, Interviewee, Properties of a Garden Window. [Interview]. 5 April 2012.
[6] Environment Canada, "Canadian Climate Normals 1971-2000: Victoria International Airport
Weather Station," 14 March 2012. [Online]. Available:
http://climate.weatheroffice.gc.ca/climate_normals/results_e.html?stnID=118&lang=e&d
Code=1&StationName=VICTORIA&SearchType=Contains&province=ALL&provBut=&month
1=0&month2=12. [Accessed 10 April 2012].
[7] E. Peterson and J. J.P. Hennessey, "On the use of power laws for estimates of wind power
potential," Journal of Applied Meteorology, vol. 17, pp. 390-394, 1978.
13
Appendix A – Window Data
Table 3 - Window dimensions, directions, and types
Window Code
Height (m)
Width (m)
Area (m^2) Direction
No. of Windows
Window Type
1 - - 2.70 W 1 PAD
2 1.98 1.80 3.56 W 2 HS
3 0.84 1.15 0.97 W 1 HS
4 1.76 1.15 2.02 W 2 PAD
5 1.15 1.76 2.02 W 1 HS
6 0.85 0.85 0.72 N 2 PAD
7 1.00 1.46 1.46 E 3 HS
8 0.54 1.15 0.62 E 3 PAS
9 1.27 0.51 0.65 E 2 SL
10 1.15 1.45 1.67 S 1 HS
11 0.85 0.85 0.72 S 1 PAD
12 0.84 1.15 0.97 S 1 HS
Table 4 - Generic U-Factor and SHGC values for existing windows according to NFRC standards
HS PAS PAD SL
U-Factor 3.081 3.208 3.106 3.415
SHGC 0.598 0.571 0.593 0.610
Table 5 - U-Factor and SHGC values for Low-E 272 Argon filled according to manufacturer specifications
HS PAS PAD SL
U-Factor 1.820 1.650 1.650 1.760
SHGC 0.340 0.270 0.270 0.330
14
Appendix B – Heat Loss Results
Table 6 - Energy flow through existing windows
Monthly and Average Energy Flow Through Existing Windows (W)
1 2 3 4 5 6 7 8 9 10 11 12
January -107.9 -141.1 -38.2 -161.7 -80.1 -61.5 -173.4 -77.2 -57.1 -64.9 -28.4 -37.6
February -94.4 -123.4 -33.4 -141.6 -70.1 -56.6 -151.6 -67.8 -50.2 -56.0 -24.5 -32.4
March -80.5 -105.2 -28.5 -120.7 -59.7 -49.8 -129.2 -58.0 -42.9 -47.2 -20.7 -27.4
April -59.5 -77.6 -21.0 -89.2 -44.1 -39.0 -95.3 -43.0 -31.8 -34.2 -15.0 -19.8
May -34.5 -44.9 -12.2 -51.7 -25.5 -25.6 -55.1 -25.2 -18.6 -18.9 -8.3 -11.0
June -12.8 -16.5 -4.5 -19.2 -9.4 -13.9 -20.2 -9.8 -7.2 -5.7 -2.5 -3.3
July 5.3 7.3 2.0 7.9 4.1 -4.9 8.9 3.1 2.3 5.7 2.4 3.3
August 6.6 8.9 2.4 9.8 5.1 -4.9 11.0 3.9 2.9 6.7 2.8 3.9
September -13.0 -16.7 -4.5 -19.5 -9.5 -15.7 -20.5 -10.1 -7.4 -5.3 -2.4 -3.1
October -52.5 -68.4 -18.5 -78.7 -38.9 -34.6 -84.1 -38.0 -28.1 -30.2 -13.2 -17.5
November -87.6 -114.6 -31.1 -131.4 -65.1 -51.2 -140.8 -62.8 -46.5 -52.4 -22.9 -30.3
December -106.9 -139.8 -37.9 -160.2 -79.4 -60.6 -171.8 -76.5 -56.6 -64.4 -28.2 -37.3
Yearly Average -53.1 -69.3 -18.8 -79.7 -39.4 -34.9 -85.2 -38.5 -28.4 -30.6 -13.4 -17.7
15
Table 7 - Energy flow through Low-E Argon filled windows
Monthly and Average Energy Flow Through Low-E 272 Argon Filled Windows (W)
1 2 3 4 5 6 7 8 9 10 11 12
January -57.8 -83.5 -22.6 -86.7 -47.4 -32.7 -102.7 -39.9 -29.4 -38.5 -15.3 -22.3
February -51.0 -73.2 -19.8 -76.5 -41.6 -30.0 -90.0 -35.2 -25.7 -33.3 -13.3 -19.3
March -43.7 -62.5 -16.9 -65.6 -35.5 -26.5 -76.8 -30.2 -22.0 -28.1 -11.3 -16.3
April -32.6 -46.2 -12.5 -48.9 -26.3 -20.7 -56.8 -22.5 -16.2 -20.4 -8.3 -11.8
May -19.3 -26.9 -7.3 -29.0 -15.3 -13.6 -33.1 -13.3 -9.4 -11.4 -4.8 -6.6
June -7.8 -10.1 -2.7 -11.7 -5.7 -7.4 -12.4 -5.4 -3.5 -3.6 -1.7 -2.1
July 1.7 3.9 1.0 2.6 2.2 -2.6 4.7 1.2 1.4 3.1 0.9 1.8
August 2.3 4.8 1.3 3.4 2.7 -2.6 5.9 1.6 1.7 3.7 1.1 2.1
September -8.2 -10.4 -2.8 -12.2 -5.9 -8.3 -12.7 -5.6 -3.6 -3.4 -1.7 -2.0
October -28.8 -40.8 -11.1 -43.2 -23.2 -18.4 -50.1 -19.9 -14.3 -18.0 -7.3 -10.4
November -47.2 -67.9 -18.4 -70.7 -38.6 -27.2 -83.5 -32.5 -23.9 -31.1 -12.4 -18.0
December -57.3 -82.8 -22.4 -85.8 -47.0 -32.2 -101.7 -39.5 -29.1 -38.2 -15.1 -22.1
Yearly Average -29.1 -41.3 -11.2 -43.7 -23.5 -18.5 -50.8 -20.1 -14.5 -18.3 -7.4 -10.6
16
Appendix C – Average Monthly Weather Data
Table 8 - Local monthly temperature, wind, and irradiance conditions [4], [6]
Mean Temperature
(°C)
Mean Wind Speed
(m/s) Wind
Direction
Irradiance North
(W/m^2)
Irradiance South
(W/m^2)
Irradiance West
(W/m^2)
Irradiance East
(W/m^2)
January 3.8 2.64 W 0.00 5.47 4.39 4.39
February 4.9 2.72 W 0.00 8.78 7.02 7.02
March 6.4 2.69 W 0.00 9.83 7.85 7.85
April 8.8 2.64 W 0.00 10.55 8.42 8.42
May 11.8 2.56 W 0.00 10.40 8.32 8.32
June 14.4 2.42 E 0.00 10.30 8.24 8.24
July 16.4 2.22 E 0.00 11.34 9.07 9.07
August 16.4 2.06 E 0.00 12.35 9.86 9.86
September 14.0 1.94 W 0.00 12.74 10.19 10.19
October 9.8 2.14 W 0.00 9.43 7.56 7.56
November 6.1 2.69 W 0.00 6.23 4.97 4.97
December 4.0 2.81 W 0.00 4.93 3.96 3.96
17
Appendix D – Financial Data
Table 9 - Inflation adjusted annual savings
Years
Existing Windows
Annual Power Costs
Replacement Windows
Annual Power Costs
Annual Savings
1 $454.56 $172.22 $282.34
2 $468.20 $177.39 $290.81
3 $482.24 $182.71 $299.53
4 $496.71 $188.19 $308.52
5 $511.61 $193.84 $317.78
6 $526.96 $199.65 $327.31
7 $542.77 $205.64 $337.13
8 $559.05 $211.81 $347.24
9 $575.82 $218.16 $357.66
10 $593.10 $224.71 $368.39
11 $610.89 $231.45 $379.44
12 $629.22 $238.39 $390.82
13 $648.09 $245.54 $402.55
14 $667.54 $252.91 $414.63
15 $687.56 $260.50 $427.06
16 $708.19 $268.31 $439.88
17 $729.44 $276.36 $453.07
18 $751.32 $284.65 $466.67
19 $773.86 $293.19 $480.66
20 $797.07 $301.99 $495.08
21 $820.99 $311.05 $509.94
22 $845.62 $320.38 $525.24
23 $870.98 $329.99 $540.99
24 $897.11 $339.89 $557.22
25 $924.03 $350.09 $573.94
26 $951.75 $360.59 $591.16
Total $10,885.07
18
Table 10 - Low-E Argon filled replacement window costs
Window Code
No. of Windows
Cost Per Window Sum
1 1 568.00 568.00
2 2 1200.00 2400.00
3 1 382.00 382.00
4 2 570.00 1140.00
5 1 488.00 488.00
6 2 310.00 620.00
7 3 406.00 1218.00
8 3 327.00 981.00
9 2 340.00 680.00
10 1 454.00 454.00
11 1 305.00 305.00
12 1 348.00 348.00
Total $9,584.00
Total Including Tax $10,734.08
