What is the term for the infiltration of outdoor air into a building?

The term for the infiltration of outdoor air into a building is "infiltration." Infiltration refers to the unintentional or passive introduction of outside air into a building through cracks, openings, or gaps in the building envelope. This process can be influenced by various factors, including temperature differences between the inside and outside, wind pressure, and the ventilation system in place.

Understanding infiltration is crucial in the context of utility services because it can significantly impact energy efficiency, indoor air quality, and overall climate control within a structure. Managing infiltration effectively can lead to lower heating and cooling costs, as well as improved comfort levels for occupants.

The other options do not relate to the concept of air movement from the outdoors to the indoors. Evaporation involves the transition of liquid to gas, typically concerning water, while condensation refers to the process of gas turning back into liquid, commonly associated with humidity and temperature changes. Absorption relates to one substance becoming part of another, often through chemical or physical processes, but does not describe the movement or exchange of air.