Which of the following correctly defines the term 'infiltration' in building design?

In building design, the term 'infiltration' specifically refers to uncontrolled air entering a building through various openings, cracks, or unsealed joints in the building envelope. This uncontrolled entry of outside air can significantly affect the building's energy efficiency by increasing heating and cooling loads, leading to higher energy costs.

The focus on infiltration emphasizes how air movement can impact indoor air quality and thermal comfort, as unwanted drafts and fluctuations in temperature can occur when air infiltrates the building. By controlling infiltration, builders can improve energy efficiency, enhance occupant comfort, and create a more sustainable structure.

Understanding the differences between infiltration and other related terms is also important. For instance, heat loss through building materials is a different concept that pertains to thermal performance, while moisture penetration from outside relates more to issues of waterproofing and building envelope integrity. Air escaping through cracks highlights a form of air leakage that occurs from inside to outside, but it does not define infiltration itself, which specifically involves air entering the building. Thus, the correct understanding of infiltration plays a crucial role in effective building design and performance management.