Why Air Sealing Matters

Reducing the amount of air that leaks in and out of your home is a cost-effective way to cut heating and cooling costs, improve durability, increase overall comfort, and create a healthier indoor environment.

Air leakage, or infiltration, is one of the most important energy-efficiency measures.

It’s not surprising that all high performance building certification programs have air sealing requirements. Homes with high air leakage rates need to compensate with larger HVAC equipment to keep the home comfortable. That HVAC equipment has to run longer to continually heat/cool the air leaking into or out of the house. Think about a sieve being filled at a sink. If the holes in the sieve are large, the faucet has to run more to keep water in the sieve. If we could make the holes in the building envelope smaller we could keep more of the heated/cooled air inside.

Moving beyond HVAC, air leakage is the method which up to 98% of water vapor moves into a building. This unwanted moisture can cause building failures which can result in significant repair costs. Homes with high air leakage also let in more dust, allergens, and pollutants resulting in poor indoor air quality.

Air sealing

Leaky house
Typical Leaky Home With Poor Air Barrier System

Why Does That Matter? Because Air Leakage…

  1. Is typically the largest driver of energy use in the home, comprising 30% – 70% of energy wasted on heating and cooling

  2. It is usually the biggest contributing factor for drafts, hot/cold spots, and other comfort issues in a home

  3. Often the largest contributor to moisture problems, especially mold and mildew

“There aren’t any climates and there aren’t any buildings that will not benefit from moisture management through air-sealing.”

Peter Yost – Founder of Building-Wright and Technical Director of Green Building Advisor

Manage Vapor Diffusion

AeroBarrier removes the air leakage by which the vapor would be transported, stopping diffusion in its tracks.

vapor diffusion

Water vapor diffusion is the movement of water vapor through vapor-permeable materials. Vapor diffusion happens through a solid material even when the material has no holes. A typical example of vapor diffusion happens when a material, such as gypsum drywall installed on a wall, separates two zones. If the air on one side of the drywall is very damp, and the air on the other side of the drywall is very dry, diffusion will occur. The drywall will absorb moisture on the damp side and then evaporate it through the dry side.

Building Science Corporation paper RR-0412: Insulations, Sheathings and Vapor Retarders, displays the potential water intrusion from just a small air leak can be up to 90 times greater than the water that would normally diffuse through gypsum board into the enclosure.