In typical homes, air leaks are often found at cracks, small holes, and penetrations for plumbing, wiring, lighting, and ductwork. Together, these leaks can add up to as
much air loss as having an open window! It’s easy to imagine how this can increase a homeowner’s utility bills and reduce comfort.
Sealing a home’s envelope—its exterior walls, ceiling, and floors—is an important step in controlling the indoor environment and lowering energy bills. The goal is to reduce air leakage as much as possible, while providing ventilation as needed for fresh air. In other words, “build it tight and ventilate it right.”
BENEFITS OF AIR SEALING
• Improved Comfort. Drafts felt during the winter are often the result of unsealed cracks and holes. Sealing homes tightly typically results in fewer drafts and less noise.
• Lower Utility Bills. Air leakage and improperly installed insulation can
waste 20 percent or more of the energy used to heat or cool a home. With effective air sealing and insulation, heating and cooling systems will not need to work as
hard. This typically means that they last longer as well
• Improved Indoor Air Quality. A tighter home envelope reduces the amount of
Humidity, dust, pollen, and pests that can enter the home and helps improve
Indoor air quality.
• Increased Durability. When warm air leaks through a home’s floors, walls, and attic, it can come in contact with cooler surfaces where condensation can occur. Moisture that occurs in these construction assemblies encourages mold growth, ruins insulation, and even compromises the structural elements of the home. Reducing air leakage helps minimize moisture problems and increase the home’s durability.
LOCATION OF COMMON AIR LEAKS
While poorly sealed windows and doors can contribute to air leakage, the bigger sources are typically holes and penetrations through the home’s envelope that are hidden from view. These include penetrations for piping, wiring, lighting, and ductwork as well as seams where materials join. It is easiest to seal these areas during construction because access is much more limited afterwards. Builders can use a variety of products to seal a home’s envelope, such as caulks, foams, gaskets, weather stripping, door sweeps, and house wraps. For homes that are sealed very tightly, mechanical ventilation systems are available to provide a controlled amount of fresh air.