Air Permeability

A quantitative measure of how easily air passes through a building envelope or component under a specified pressure difference, usually reported as volumetric flow per unit area at a reference pressure (e.g., m³·h⁻¹·m⁻² at 50 Pa) or as a whole‑building normalized leakage (m³·h⁻¹·m⁻² or n50). It characterizes uncontrolled leakage paths, not designed ventilation.