Please explain the U- and R-values and how they rate a windows insulation capabilities?
U-value represents a products resistance to heat transfer and is a measurement of the total insulating ability of a window or patio door. It is used to measure all of the components that are part of the window or patio door: the frame, the spacer that divides the two panes of glass, and the glass itself. Anything else, like coatings on the glass or the air or gases that might be used in the space between the two panes are also part of a U-value calculation. The smaller the U-value is, the slower the transfer of heat across a window. R-value (used in wall and ceiling insulation evaluation) is much like a U-value, but represents the entire unit and is the reciprocal of the U-value (U = 1/R), so the higher the R-value, the slower the transfer of heat occurs and the greater the insulation.
