What is an R-5 Window?
R-5 windows are highly insulating windows with a whole-window R-value of 5 (or a U-factor of around 0.2) and are the top tier of energy-efficient windows for cold and mixed climates available today.

What is an R-value and U-factor?
An R-value indicates an insulation's resistance to heat flow. So, the higher the R-value, the greater the insulating effectiveness. U-factor is the inverse of R-value. So, the lower the U-factor, the better the thermal performance of the...

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