What is a pressure boundary?

A pressure boundary refers specifically to the primary barrier in a building that separates indoor air from outdoor air. This boundary plays a crucial role in maintaining a controlled indoor environment by managing air leakage, which can significantly affect energy efficiency, comfort, and indoor air quality. The pressure boundary typically includes elements such as walls, windows, doors, and the roof, which work together to limit the movement of air between the inside and outside of a structure.

The other choices, while related to building performance concepts, do not accurately define the pressure boundary. For example, a barrier separating heated from unheated spaces may contribute to thermal performance but does not encompass the full concept of a pressure boundary. The area of highest airflow is a condition that may occur due to factors like stack effect or wind pressure, but it does not describe a specific boundary or barrier. Lastly, an insulation type used in colder climates refers to materials designed to improve thermal resistance rather than being a characteristic of the pressure boundary itself.