Air Sealing helps to create a continuous air barrier that provides resistance to the flow of air (and moisture) between the inside and the outside of the house (and into the walls). Undertaking air sealing can reduce home energy bills and make homes less drafty and more comfortable.

In the majority of homes, the most significant air leaks are found in the attic/top floor and basement/lowest floor. This is due to the stack effect: in a heated home, less dense warm air rises and expands, creating a higher-pressure area near the top of the house. In colder months, this higher pressure pushes air out through cracks at the top of the house (exfiltration) and reduces the pressure at the bottom of the house, drawing in cold outdoor air (infiltration).

When conducting air sealing, it is important to prioritize the locations that will allow for bigger reductions in air leakage and reduce the negative impacts of the stack effect. High priority areas often include, in this order: big holes, regardless of location; smaller holes at top floor ceiling or attic; smaller holes on bottom floor; and smaller holes on main floors.

Legend

1. Air Sealing
2. Insulation
3. High Efficiency Ventilation System
4. Efficient Windows and Doors
5. Efficient Heating Systems

HAAS Consideration: Undertaking air sealing without adding appropriate and sufficient ventilation may create new issues with high levels of humidity in the home, condensation on windows, moisture accumulation in walls and attic, and mould growth and/or insufficient air circulation for a heathy home.