Air Permeability refers to the property of a material or building component that allows air to pass through it. It measures the ease with which air can penetrate or infiltrate through the surface or structure. It is a significant factor in assessing the airtightness and energy efficiency of buildings.
The air permeability of a material or component is typically quantified by measuring the air flow rate passing through a specific area under a standardised pressure difference. The results are expressed as a volume flow rate per unit area, such as litres per second per square meter (L/s/m²) or cubic feet per minute per square foot (CFM/ft²).
Air permeability is an important consideration in building design, construction, and energy performance. It affects the building’s overall airtightness, energy consumption, indoor comfort, and indoor air quality. Excessive air permeability can result in higher energy losses, increased heating and cooling demands, and reduced thermal comfort.
Controlling air permeability is achieved through the use of appropriate materials, proper sealing techniques, and the implementation of air barrier systems. Air barrier materials, such as membranes, tapes, sealants, and coatings, are employed to minimize air leakage and enhance airtightness.
By reducing air permeability and improving airtightness, building owners and professionals can enhance energy efficiency, reduce heating and cooling loads, minimise draughts, improve thermal comfort, and promote better indoor air quality by controlling the infiltration of outdoor pollutants, allergens, and moisture.
Building codes, standards, and energy efficiency programs often specify maximum air permeability requirements for different components and assemblies. Testing methods L1A and L2A are used to evaluate and quantify the air permeability of materials and building envelopes.