Windows lose and gain heat by conduction, convection, radiation and air leakage. This heat transfer is expressed with U-values, or U-factors. U-values are the mathematical inverse of R-values. So an R-value of 2 equals a U-value of 1/2, or 0.5. Unlike R-values, lower U-value indicates higher insulating value.
Conduction is the movement of heat through a solid material. Touch a hot skillet, and you feel heat conducted from the stove through the pan. Heat flows through a window much the same way. With a less conductive material, you impede heat flow. Multiple-glazed windows trap low-conductance gas such as argon between panes of glass. Thermally resistant edge spacers and window frames reduce conduction, too.
Heating Season Savings
In climates with a significant heating season, windows have represented a major source of unwanted heat loss, discomfort, and condensation problems. In recent decades, windows have undergone a technological revolution. It is now possible to have lower heat loss, less air leakage, and warmer window surfaces that improve comfort and minimize condensation.
Cooling Season Savings
In climates that mainly require cooling, windows have represented a major source of unwanted heat gain. In recent years, low-E coatings that reject solar heat without darkening the glass have undergone a technological revolution. It is now possible to significantly reduce solar heat gain and improve comfort while providing clear views and daylight.
Advanced Window Corp., 4935 W. Le Moyne St. Chicago IL 60651 Ph # 773-379-3500 Fax # 773-379-4060 E-mail: firstname.lastname@example.org