What is the meaning of U-value?
The U-value is a measurement used to quantify how quickly heat is lost through a material. The lower the U-Value, the less heat loss, and the greater the insulation. In more technical terms, the U-value is the amount of conductive heat energy (Btu’s) transferred through 1ft2 of a specific insulating unit for each 1 degree F temperature difference between the indoor and outdoor air. It is the inverse of the R-value; U = 1/R. As the U-value decreases, so does the amount of heat that is transferred through the glazing material. The lower the U-value, the more restrictive the fenestration product is to heat transfer.
