What does leakage refer to in building terms?

Leakage in building terms specifically refers to the unintended entrance or escape of water or air. This phenomenon is critical in assessing the performance and integrity of a building's envelope, which includes roofs, walls, and foundations. When leakage occurs, it can lead to several issues, such as moisture damage, mold growth, and decreased energy efficiency.

Understanding leakage is fundamental in the context of roofing, where proper installation and maintenance of roofing materials are necessary to prevent water intrusion. This is particularly crucial in Illinois, where weather conditions can vary dramatically, impacting the performance of roofing systems.

In contrast, the other options do not accurately define leakage. Controlled entrance or exit of air pertains to ventilation strategies, which aim to improve indoor air quality and energy efficiency without the downsides of unregulated leakage. Sealing materials describe techniques used to prevent leakage rather than the concept of leakage itself. The measurement of insulation quality relates to thermal performance but does not involve the aspects of unintended flow associated with leakage.