Air infiltration (AI or air leakage) is the passage of air in or out of a building. This happens through cracks and gaps in the outside shell. Poor insulation around windows, doors, and vents contribute to air infiltration as well. Any home energy audit will test first for air infiltration. The lower the air infiltration number, the more airtight your home or building.

What does it actually mean for my home?

According to an ENERGY STAR website estimate, air leakage accounts for 25–40% of the energy used for heating and cooling in a typical home. For example, in today’s homes, builders use products such as house wraps, sealants, foams, and tapes to tighten the home’s envelope to reduce air infiltration. However, this was not always common practice. Homes built before the 21st century could have air infiltration problems. One of the biggest culprits for air infiltration is your windows, especially in older homes.

House Showing Causes of Air Infiltration

Defending against air leakage

Modern windows have advanced weather stripping and engineered sash locking technology helps reduce energy. Harvey energy-efficient windows have some of the industry’s lowest AI rates.

The industry standard for air leakage is 0.3cfm (cubic feet per minute) or the equivalent of 2.25 gallons of air per minute. Harvey windows average 0.05cfm or .375 gallons of air per minute.

Additional Resource

For more on what makes a window energy efficient or view our post on Understanding a Windows Thermal Performance Rating.

Other options to help reduce air infiltration

We understand that replacing windows is not an option for everyone. Harvey offers storm windows as well. They are easy-to-operate, self-contained units that provide extra insulating value. We custom fit the exact dimensions of your existing windows. Storm windows are a lower cost option to help seal those windows.


Remember a tighter house construction can improve the energy efficiency, but also air quality, and comfort of your home by eliminating unwanted drafts. Tighter home construction can offer you:

  • Improved comfort — reduces drafts, noise, and moisture.
  • Improved indoor air quality — keeps dust, pollen, car exhaust, and insects out of the home.
  • Lower costs — reduces the escape of conditioned air.

Ready to improve your home by reducing air infiltration? Find, compare and get quotes from contractors through the Harvey ProZone.

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