What does exfiltration refer to in building environments?

Exfiltration in building environments specifically refers to uncontrolled outward air leakage. This process typically occurs when indoor air escapes through various openings or cracks in a building’s envelope. This can happen due to differences in pressure, such as when warm, conditioned air inside a building is less dense than the outside air, leading to an imbalance that causes air to flow out.

Understanding exfiltration is essential for energy efficiency and maintaining indoor air quality in HVAC design. Excessive exfiltration can result in loss of conditioned air, leading to higher energy costs, unintended drafts, and potential moisture issues as warm air escapes, which could then bring in outdoor air that is humid or contains pollutants. Managing exfiltration often involves proper insulation and sealing of penetrations, ensuring that the building remains energy-efficient while maintaining comfort for its occupants.