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Existing Homes in Chicago: Chicago, IL
Six homes that were located within a 15 mile (25 km) radius of each other, south of downtown Chicago, were identified through a local weatherization program. Each home was a single-family detached structure with single-pane windows (with or without storm windows). All homes were constructed between 1920 and 1970. All had their original single-pane windows. Four of the six homes had limited remaining storm windows and two had nearly 90 percent of the storm windows intact. All of the homes were typical Chicago construction for the period in which they were built. All had brick façades with structural concrete block exterior walls and no insulation in the walls. All had basements that were either directly or indirectly conditioned. More details about each individual house can be found in Table 1.
Table 1: Detailed House Characteristics
| House |
# Stories |
Heater Type |
Year Built |
Building Type |
Conditioned S.F. (sq. meters) |
Window Area s.f. (sq. meters) |
# Windows |
Before Air Tightness CFM (M3/hr) |
After Air Tightness CFM (M3/hr) |
| 1 |
1 |
Hot Water Boiler |
1930s |
Bungalow |
1,625 (151) |
132 (12.3) |
33 |
5,230 (8,891) |
4,930 (8,381) |
| 2 |
1 |
Gas Furnace |
1950 |
Bungalow |
2,250 (209) |
72 (6.7) |
12 |
4,759 (8,090) |
4,459 (7,580) |
| 3 |
2 |
Gas Furnace |
1935 |
Bungalow |
1,125 (105) |
107 (9.9) |
11 |
3,159 (5,370) |
2,900 (4,930) |
| 4 |
2 |
Gas Furnace |
1945 |
Bungalow |
1,150 (107) |
62 (5.8) |
22 |
4,930 (8,381) |
4,595 (7,812) |
| 5 |
1 |
Gas Furnace |
1965 |
Ranch |
2,160 (201) |
58 (5.5) |
12 |
3,590 (6,103) |
3,359 (5,710) |
| 6 |
1 |
Hot Water Boiler |
1970 |
Bungalow |
2,500 (232) |
65 (6.0) |
24 |
3,850 (6,545) |
3,520 (5,984) |
All occupants were instructed not to change their thermostat settings or heating patterns during the test. This enabled a comparison of energy used by the house before and after the storm window retrofit. Data was collected in two phases. The Baseline data was collected prior to the installation of the new storm windows, and the Second Stage data was collected after the installation. Four homes were then fitted with Low-E storm windows and the remaining two homes had clear storm windows installed. Datalogging equipment was installed in each house to monitor key information including furnace runtime, indoor temperature and humidity, and surface temperatures of the primary and storm windows on an hourly basis. Although outdoor data was recorded at two homes, weather data from nearby Chicago Midway Airport was used as the basis for establishing official outdoor conditions. The data from each house was then used to characterize energy consumption with and without storm windows, which produced an equation reflecting energy usage as a function of the indoor/outdoor temperature difference. Seasonal energy use predictions based on typical meteorological conditions (assuming indoor temperature of 70°F/21°C) could then be made with before and after storm windows were installed. An air tightness test was performed with and without the storm windows to determine if the newly installed storm windows had any effect on how much air was being leaked by the homes.
Recorded data was analyzed for each house to determine the performance with and without storm windows. Trend lines were developed from the data to show the relationship between the two configurations, as shown in Table 2. The vertical distance between the lines is assumed to be the corresponding daily energy savings for the storm windows. By applying the difference in the trend equation and overlaying that with ASHRAE hourly bin data for Chicago, the energy savings can be calculated over the period of a year to determine annual savings and simple payback.
Table 2
- Datalogging equipment was fully commissioned for five of the six houses in late October 2005
- New storm windows were installed in January and early February 2006
- Second Stage data collected between February and April 2006
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