Sealing openings in a home’s envelope—its exterior walls, ceiling and floors—is an important step in controlling the indoor environment and lowering utility bills. Air leakage can waste 30 percent or more of the energy used to heat or cool a home. With effective air sealing, heating and cooling systems will not need to work as hard.

In addition, drafts felt during winter are often the result of unsealed cracks and holes. A tighter home envelope also reduces the amount of humidity, dust, pollen, and pests that can enter the home, helping to improve indoor air quality. And reducing air leakage can help reduce moisture problems and increase the home’s durability.

Testing showed that the Joliet home was somewhat leaky at 0.57 air changes per hour, making the house a bit drafty and in winter. Air leaks were found mostly through and around the old windows that did not have any storm panes. Leaks were also found around the attic hatch and ceiling. Since this extra outdoor air had to be heated or cooled, it increased the home’s total energy consumption.

In addition, the attic was inadequately insulated with an R-value of 9, much lower than the recommended R value of 43 for the Joliet area. This lack of adequate insulation increased energy consumption and contributed to discomfort in the upstairs rooms by creating drafty areas with cold spots in winter and hot spots in summer.

To tighten the envelope, new storm windows were installed, caulking around the new storms was performed and the attic insulation was upgraded to an R-value of 43. Air leaks through ceiling openings to the attic were sealed.  We anticipate the air change per hour to drop to 0.35.

Estimated Energy Savings

The annual energy savings seen for air sealing, storm windows,  and attic insulation was 14.3 percent of the total energy used by the home. The savings seen consisted primarily of heating savings of 257 therms, or $280.

However, when all energy-saving measures are implemented together, the analysis shows an estimated annual energy savings of 41 percent (a combined 600 kWh and 701 therms). This translates into a net $54 electric and $764 natural gas savings, or a total of $818/year.

The total savings is not the sum of all the individual measures because of interactions between the measures. For example, replacing incandescent lights with compact fluorescent lights saves electric energy but because the compact fluorescent light gives off less heat, the heating bill increases somewhat. As the number of measures increase these interactions become more complex.