Rating criteria and standards—windows, doors and skylights

How is your fenestration product measured?

Rating for energy performance

In Canada, the energy performance of windows, doors and skylights is tested using the Canadian Standards Association (CSA) A440.2 standard.

(Some products sold in Canada may also be tested using the standards of the National Fenestration Rating Council in the United States.)

In Canada, energy performance is rated using the following values:

  • U-factor—the rate of heat transfer from warm to cold areas in watts per square metre Kelvin (W/m2K) or in British thermal units per hour per square foot Fahrenheit (Btu/h x sq. ft. x °F). In either case, the lower the number, the more efficient the product.
  • Solar heat gain coefficient (SHGC)—a ratio showing the amount of the sun’s heat that can pass through the product. The higher the number, the more solar heat the product gains.
  • Energy Rating (ER)—a value demonstrating the balance between U-factor, SHGC and air leakage. The higher the number, the more efficient the product. (This value applies to windows and doors only.)
  • R-value—a value indicating the resistance to heat transfer in square feet per hour in degrees Fahrenheit per British thermal unit (sq. ft. x h x °F/Btu). The higher the number, the more efficient the product.
    (The R-value is not part of the energy performance standards, but is often quoted by contractors and sales staff as a measure of performance.)
  • Visible transmittance (VT)—a ratio of the amount of visible light that can pass through a product. The higher the number, the more light can pass through.
  • Centre-of-glass rating—an energy-efficiency value that refers only to the glass portion of a product and not the product as a whole.

Rating for physical performance

Canadian building codes require that all windows and doors be rated for their physical performance before being installed in new homes or buildings. Minimum air leakage, water tightness and structural strength ratings vary between provinces, territories and municipalities, depending on climate conditions.

Canadian standards are being brought in line with the harmonized North American Fenestration Standard (NAFS) that applies to all windows, doors and skylights in Canada and the United States. Under this standard, products are assigned a performance grade based on where they are used:

  • R—single-family residential buildings
  • LC—low- and mid-rise multi-family residential and light commercial buildings
  • CW—mid-rise multifamily residential and commercial office buildings
  • AW—high-rise multifamily residential and commercial office buildings

Each product is also given a number. The higher the number, the stronger and more water-resistant the product is.


When you buy certified windows, doors and skylights, you can be sure that they have been tested against current standards by an accredited laboratory, and that those test results have been verified by an independent third party.

Windows, doors and skylights sold in Canada may be certified for energy performance by any of these accredited agencies:

Some insulated glass (IG) units also carry Insulating Glass Manufacturers Alliance (IGMA) certification. The IGMA program certifies that a manufacturer can consistently build IG units that will not fog and whose seals will not fail prematurely.