What term describes heat loss in a building due to air leakage?

The correct term for heat loss in a building due to air leakage is infiltration. Infiltration refers to the unintentional introduction of outside air into a building through cracks, openings, and other unsealed areas. This process can lead to a significant loss of heated or cooled air, thereby affecting the energy efficiency of the structure. Proper sealing and insulation techniques are often employed to minimize infiltration, ensuring that a building maintains its desired temperature without excessive energy consumption.

In contrast, the term exfiltration refers to the process of air escaping from a building, which is the opposite of infiltration. Osmosis is a term primarily used in biology and chemistry, describing the movement of solvent molecules through a semipermeable membrane, and is not applicable in the context of buildings. The term negative impact, while it can describe a range of adverse effects, does not specifically reference the phenomenon of air leakage related to heat loss in buildings.