Air infiltration (window / door rating)
Air infiltration is the leakage through closed windows and doors at test pressure, rated under AS 2047. Lower values mean better NCC 2022 thermal envelope.
Ask Chalkline about this →Air infiltration is the rate of air leakage through a closed window or external door at a defined test pressure, measured under AS 2047:2014 and reported in litres per second per square metre of operable area (L/s/m²) at 75 Pa pressure difference.
A lower value means a tighter seal and a more energy-efficient window or door. The result is published on the manufacturer’s WERS label (Windows Energy Rating Scheme) and feeds the NatHERS thermal model for the building.
Why it matters under NCC 2022
The NCC 2022 energy efficiency standard for Class 1 buildings requires a NatHERS rating of 7 stars or higher (Part H6). Air infiltration through windows and doors is a meaningful contributor to the heating and cooling demand the rating models. The tighter the window seals, the smaller the heat-loss term in the calculation and the easier it is to hit 7 stars without over-specifying glazing or insulation.
Acoustic isolation tracks the same way: air paths transmit sound, so a low air-infiltration window also performs better against external noise.
Indicative values
| Window type | Typical air infiltration (L/s/m²) at 75 Pa |
|---|---|
| Premium awning / casement with compression seal | 0.5 or less |
| Standard awning / casement | 1.0 to 1.5 |
| Standard sliding window | 2.0 to 3.5 |
| Standard sliding door | 2.0 to 4.0 |
Compression-sealed openings (awning, casement, hinged door) generally test lower than sliding equipment because the seal compresses to a positive contact rather than relying on a brush or fin to wipe against the frame.
Where the rating fails on site
The factory-tested rating is the best-case scenario for that product. Site issues that degrade it:
- Frame not square in the opening: gaps between seal and frame surface increase leakage path.
- Wall wrap not lapped over the head flashing: air bypasses the window through the framing.
- Sealant gun joints inside and outside not complete: air-paths persist around the frame even with a tight sash.
- Old or damaged seals on a refurb: rubber and brush seals harden in 10-15 years and stop sealing.
A well-rated window installed poorly performs worse than a worse-rated window installed well.
Also known as: air leakage rate, window air infiltration, AS 2047 air infiltration.
Category: Compliance / NCC / windows.
Related
See also
Last updated: 2026-05-16. Verified: 2026-05-16.