Note 40. Building Air Leakage
Air leakage through the exterior skin, structure, and openings of buildings can be a major cause of energy waste. The Energy Efficiency Manual includes a group of energy conservation measures to minimize air leakage.
This Note explains concisely the causes of air leakage, which are wind pressure, chimney or stack effect, and unbalanced fan systems. It also gives practical methods for finding and estimating air leakage.
The term “infiltration” is often used for air leakage. Strictly speaking, infiltration is air leakage into the building. The less common term “exfiltration” is air leakage out of the building. Both waste energy, but only infiltration causes discomfort directly.