Airtightnessare

Airtightnessare is a term used in building physics to describe an area-normalized measure of airtightness, intended to compare how tightly different defined areas—such as a building envelope, a room, or a component assembly—limit air leakage. It is a neologism and not part of formal standards, but it appears in technical discussions and some research papers as a way to combine leakage rate with the size of the area.

Definition and calculation: Under a standardized pressurization test, the leakage rate Q is measured at a given pressure difference ΔP (commonly 50 Pa). The airtightnessare value is defined as Q divided by the enclosed area A: airtightnessare = QΔP / A. The resulting units are cubic meters per hour per square meter (m3/h/m2). A lower value indicates a tighter area.

Applications and considerations: The metric is used to compare the relative airtightness of different assemblies or building sections, and can inform ventilation design and energy modeling. However, it has limitations: leaks may not scale linearly with area, leak location matters, and pressure-dependent leakage behavior may vary with ΔP. Because it is not standardized, comparisons should specify test conditions and area definitions.

Relation to standard metrics: Airtightnessare complements standardized measures such as ACH50 or n50, which refer to air changes per hour or flow per pressure independent of area, and are typically used for whole-building assessments. Airtightnessare focuses on area-normalized leakage and is primarily used in research, design optimization, or for subdividing large spaces.