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U-factor can be expressed in metric units (W/m2·K) or imperial inch-pound units (Btu/h·ft2·F).

To convert imperial u-factors to metric u-factors, multiply by 5.678.

Example: My contractor has given me a quote for five new windows that I would like to replace. My contractor says they have a U-factor in imperial units (Btu/h·ft2·F) of 0.21 and I want to know what that is in metric units.

0.21 x 5.678 = 1.19 (W/m2·K)

New windows typically have a U-factor between 1.00 and 1.80 (W/m2·K), which converts to between 0.18 and 0.32 (Btu/h·ft2·F).

In order to receive a window rebate through the CleanBC Better Homes and Home Renovation Rebate Program, your windows must be ENERGY STAR® certified, have a metric U-factor (W/m2·K) of 1.23 – 1.4 for Tier 1 rebates or a metric u-factor (W/m2·K) of 1.22 or less for Tier 2 rebates and be listed on Natural Resource Canada’s ENERGY STAR certified fenestration product list.  Learn more about this rebate here.