The Mystery of Air Leakage

Air leakage causes curiously high heating and cooling costs in buildings that are supposed to be energy-efficient. This shouldn’t be a mystery. You can’t achieve airtightness without trying. Airtightness has never been a goal of the building construction industry, and that isn’t changing. Most buildings, both homes and larger buildings, don’t really have an air barrier.

An air barrier is a material that is itself airtight. Drywall, plywood, steel paneling, are air barriers. Concrete block, fibrous insulation, and tar paper aren’t air barriers.

An air-barrier material comes in pieces so the seams must be sealed or you’ll have leaks there. Most builders and remodelers don’t know how to install air barriers. Testing buildings with a blower door is really the only way to verify that a building is sufficiently airtight. At Saturn we’ve been leak-testing buildings since 1987, but blower-door testing is still rare out on the world’s construction and remodeling projects.

Do walls help with air leakage?

Walls are generally more airtight than ceilings and floors. Most of this leaking air moves through large gaps in the top and bottom of the building. These gaps are easy to seal during construction, and more difficult later.

The International Energy Conservation Code (IECC 2009 and later) has an air-sealing standard. A builder can either have the building tested or have a visual air-sealing inspection from a building inspector. Ignorance of the code, untrained building inspectors, and a lack of qualified testing contractors are barriers to compliance with this IECC standard.

Builders worry about fresh indoor air, as well they should. However, the best way to provide fresh air is through a fan-powered ventilation system that controls the exchange of indoor and outdoor air. If you let the weather and air leaks do your ventilation, you’ll waste a whole lot of energy. When building or remodeling: Seal the building tight and ventilate it right!

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