Local Knowledge About Window Treatment

While heat is gained through most windows during the day, needed heat escapes through windows at night. The average home loses 10 to 25 percent of its heat through windows. This percentage may be even higher for passive solar homes because they usually have larger window area, although these homes also gain more heat if properly designed. Movable insulation is a device such as an insulative shade, shutter, panel, or curtain that reduces heat loss at night and during cloudy periods, and heat gain during the day in warm weather. When used properly, movable insulation can increase or decrease net heat gain, depending on user needs. Most movable insulation improves the energy efficiency of windows by creating an air space between the insulating material and the window. The air space acts as an insulator and reduces heat losses caused by convection and conduction. The insulating material in the movable insulation also lowers heat loss caused by conduction. This is only effective if air does not leak around the insulation, so you should tightly seal the movable insulation around the window frame.