NAFS and CSA-A440S1

What Is It?

In 1980, Fenestration Canada realized there was a need for an all-encompassing standard for window performance, regardless of the materials used to manufacture the window. A Canadian Standards Association (CSA) committee was formed and it developed the CSA-A440 Window Standard. It was first published in 1984 and has been updated since then to reflect new technologies and to harmonize with US standards. The new standard is referred to as NAFS (North American Fenestration Standard) and there is a Canadian Supplement called A440S1.

NAFS sets minimum standards for air tightness, water tightness, wind resistance, forced entry resistance and ease of operation. It also sets minimum requirements for all components and their materials from hardware, insect screens and weatherstripping to finishes and adhesives.

The National Building Code of Canada and most provincial building codes require that windows meet NAFS specifications. Each window product line must be tested by an independent laboratory and meet minimum performance standards in three areas critical to performance: air tightness, water tightness and wind resistance. The results of the tests are then published. Consumers should ask for and be shown these test results.

Air Tightness (or Air Leakage) Test

This test is performed at a test pressure that represents a 40 km/h wind. The window leakage is measured in liters per second per square meter. 1.5 l/s/m2 is the maximum leakage that is allowed with the A3 level being 33% of the A2 maximum.

Air Tightness

Water Tightness (or Water Leakage) Test

The water leakage test is performed by spraying the window with a constant stream of water, raising the test pressures to simulate increasing wind loads, and observing if any water gets inside the patio door. Each performance grade represents wind load starting at 58 km/h and rising incrementally. Because different parts of Canada have different wind loads and these have been measured and published, the National Building Code requires different minimum levels in different regions.

Water Tightness

Wind Load Deflection and Structural Tests

These tests measures the deflection and permanent damage of the window components under increasing pressures, which represent higher wind loads. Check the performance grade calculator at to determine the grade needed in any location in Canada.

Pressure vs Wind Speed