Double-Glazed with Clear Glass

This figure illustrates the performance of a typical double-glazed unit with two lites of clear glass. The inner and outer layers of glass are both clear and separated by an air gap. Double glazing, compared to single glazing, cuts heat loss in half due to the insulating air space between the glass layers. In addition to reducing the heat flow, a double-glazed unit with clear glass will allow the transmission of high visible light and high solar heat gain.

Note: These values are for the center of glass only. They should only be used to compare the effect of different glazing types, not to compare total window products. Frame choice can drastically affect performance. These values represent double glazing with a 1/2" air gap. Aluminum units use 3/8" air gap, where the U-factor is 0.52 and the SHGC and VT remain the same.