Caulking is used to seal the gap between the window and the wall in which it is installed. If the caulking deteriorates, water can enter the space, resulting in damage to the window itself and to wall materials. Air entering through areas with damaged or missing caulking increases energy costs. If surfaces are properly prepared and a high quality caulking is used, it should not be necessary to recaulk windows for at least 10 years. The most widely recognized impact that windows have on facility operating budgets is their energy cost.
All new windows offer a tight fit between components to limit the rate of infiltration.
The other two types of heat loss or gain can be controlled by selecting specific features to be included in the replacement windows, including the number of glazings, the solar transmissivity of the glazings and the thermal characteristics of the window's frame. While each of these features can reduce energy loss through windows, not all will be cost-effective in all applications. The thermal efficiency of a window is one of the most important energy considerations when evaluating replacement window options. The thermal heat gain or loss through a window is determined primarily by the number of glazings. Single glazed windows have an R-value of approximately 0.88.