#WINDOWS R RATING WINDOWS#

Visible transmittance (VT)-a ratio of the amount of visible light that can pass through a 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.) The higher the number, the more efficient the product. R-value-a value indicating the resistance to heat transfer in square feet per hour in degrees Fahrenheit per British thermal unit (sq.В ft.В xВ hВ x вЏ/Btu).

#WINDOWS R RATING WINDOWS#

(This value applies to windows and doors only.) Energy Rating (ER)-a value demonstrating the balance between U-factor, SHGC and air leakage.The higher the number, the more solar heat the product gains. Solar heat gain coefficient (SHGC)-a ratio showing the amount of the sunвЂ™s heat that can pass through the product.In either case, the lower the number, the more efficient the product.

U-factor-the rate of heat transfer from warm to cold areas in watts per square metre Kelvin (W/m 2K) or in British thermal units per hour per square foot Fahrenheit (Btu/hВ xВ sq.В ft.В xВ вЏ).

In Canada, energy performance is rated using the following values: (Some products sold in Canada may also be tested using the standards of the National Fenestration Rating Council in the United States.) In Canada, the energy performance of windows, doors and skylights is tested using the Canadian Standards Association (CSA) A440.2 standard. How is your product measured? Rating for energy performance

Windows r rating