What is air leakage?

Air Leakage is the uncontrolled movement of air through gaps, cracks & openings in the building envelope.

Air Leakage should not be confused with ventilation which is controlled movement of air in and out of the building.

The two main causes of air leakage are:

• Wind - Wind blowing against or across a building changes positive and negative pressures on the building envelope
• Stack Effect - Warm air rising within a building known as the "Stack Effect" causes pressure differentials. The rising warm air reduces the pressure in the base of building, forcing cold air to infiltrate through gaps, cracks and openings in the envelope fabric