Thermal Star Windows

Thermal Star Doors

Air Infiltration Ratings Explained


Nothing is more miserable than a drafty house in winter.

Wrapping yourself in blankets to protect yourself from the breeze in your home isn’t fun for anyone.

Everyone knows that drafts come in through old, unsealed windows and doors, but did you know that drafts are something you need to consider even with new windows?

Air Infiltration (AI) Explained 

Air leakage is referred to by the Window Energy Rating Scheme (WERS) as ‘Air Infiltration’ (AI) and is measured by how much outside air is let into a home or building through a closed window or door assembly (or for that matter ducts, leakage through walls, joints, or other cracks).


AI is measured using a complicated formula that factors in air leakage coefficients, pressure differences and pressure exponents. The important thing to know is the lower the AI rating the better.

Understanding AI Ratings

With fixed windows, it is possible to achieve an AI rating of 0 – meaning that no draft at all. However, windows that open (and doors, obviously) will always have at least a small amount of Air Infiltration.


Australian Windows must meet Australian Standard 2047 – 2014 (Windows and External Glazed Doors in Buildings), which dictates a maximum infiltration of 5.0 Litres of air per second per metre squared.


But for a thermally efficient home – especially in cold climates – an AI rating much lower would help regulate the temperature in your home, saving you big on heating costs.

Getting The Right AI Rating For Your Home

The Southern Star Group offers many window and door systems with very low AI ratings in both the Southern Star Aluminium and Canterbury Timber range.


To ensure you make the right choice for your home get in touch with our team, or view our full range of windows and doors in our latest catalogue.


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