How can I convert an imperial U-factor to a metric U-factor?

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 have a metric U-factor (W/m²·K) of 1.22 or less and must be listed with one of the following certification bodies:

• Canadian Standards Association (CSA)
• Intertek Canada (Intertek)
• Labtest Certification (LC)
• QAI Laboratories (QAI)
• National Fenestration Ratings Council (NFRC)

Learn more about this rebate here.