Buying SIGA materials for self-install? We supply the full range of SIGA membranes, tapes, and accessories for airtight builds. For teams who want confidence on-site, add our optional training day.
Air permeability is the uncontrolled movement of air into and out of a building through cracks and gaps. It can account for a large share of energy waste and discomfort.
It’s expressed as air leakage in m³/(h·m²) @ 50 Pa (cubic metres per hour per square metre of envelope area, at 50 Pascals pressure). Lower is better.
Airtightness means eliminating draughts. Small gaps—under window boards, around frames, between floors, at ducts—add up. The solution is a consistent, air-resistant layer around the inside of the building.
Building envelope
External walls, windows, external doors, floors, and ceilings.
Airtightness
Resistance of the envelope to inward/outward air leakage. Excess leakage increases energy use and causes draughts.
Air leakage
Air passing through gaps/cracks in the envelope driven by pressure differences (e.g., at doors, windows, between floor levels).
Air permeability
Leakage rate in m³/(h·m²) @ 50 Pa across the envelope area, measured with a blower door fan.
Air changes per hour (ACH)
Overall ventilation rate in the building. Can be controlled via MVHR or manual openings (windows/doors).
Buy SIGA materials online. Add training if you want a first-time-right install.
