Tip 54

In addition to energy efficiency, how can I evaluate a window's or door's performance?

Refer to its North American Fenestration Standard (NAFS) test results, also called structural performance tests. This standard assesses the strength of a product with respect to the elements (e.g. wind) as well as its air and water tightness.

These tests have changed the product rating from A/B/C to a performance grade or PG. The higher the PG value, the better the performance.

In the U.S., the minimum performance levels are defined according to class. For example, according to class R, the minimum performance grade is 15.

Product performance class Minimum performance grade (PG) Minimum design pressure (DP),
Pa (psf)
Minimum structural test pressure (STP),
Pa (psf)
Minimum water resistance test pressure,
Pa (psf)
Windows and doors
R 15 720 (15.0) 1080 (22.5) 140 (2.90)
LS 25 1200 (25.0) 1800 (37.5) 180 (3.75)
CW 30 1440 (30,0) 2160 (45.0) 220 (4.50)
AW 40 1920 (40.0) 2880 (60.0) 390 (8.00)
Unit skylights, tubular daylighting devices, and roof windows
R 15 720 (15.0) 1440 30.0) 140 (2.90)
CW 30 1440 (30.0) 2880 (60.0) 220 (4.50)

In Canada, requirements are more specific. In fact, minimum levels also take geographical location and climatic conditions into account.

Therefore, before buying windows, be sure to validate the minimal performance grade (PG) imposed by your environment (e.g. region, altitude, type of terrain). Determine your minimum PG with the Building Code Fenestration Performance Calculator.

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