In older homes in wintertime, windows are often one of the largest sources of heat loss, due to their low insulating ability and high air-leakage rates. In the summer, windows are also generally the major source of unwanted heat gain. Besides improving the energy efficiency of the home, replacing old windows with new ones can enhance home comfort, eliminate winter condensation on the glass, reduce fabric fading and, in some cases, reduce the size of heating-and-cooling equipment needed.

The two most important window characteristics are U-factor and Solar Heat Gain Coefficient. U-factor relates to the window’s ability to retain heat, and the SHGC relates to the window’s ability to keep solar gain out. In both cases, the lower the rating, the better the window performance. Many new windows have the U-factor and SHGC printed right on them.

Replacing existing windows in a cost-effective manner:

Replacing the windows in a home is not always cost effective in a mixed-humid climate. Jalousie windows, metal-framed windows and single-paned windows in poor condition are the most likely candidates for replacement. The entire window unit (sash, frame and trim) need not be replaced in order to reach the desired U-factor and SHGC. Instead, sash kits can be used, usually at a lower cost than replacing the entire unit.