1. Cellular shades can reduce heat loss by up to 31 percent—if they are installed correctly. They come single, double, or triple cell; more cells means more insulation. Hang cellular shades inside the window frame, a half-inch from the glass, with gaps of only a quarter-inch on either side. Raise and lower them with the sun to take advantage of solar heat gain. Wipe down any condensation that forms overnight.
2. Sheers hung on a double rod add privacy and some light control (if not draft resistance) when shades are raised to capture the sun.
3. Drapes just by themselves cut heat loss by about 10 percent —and look nice, too. Choose ones with a tightly woven fabric and a lining. To get the best energy savings, hang curtains about an inch from the window, or as close to that as possible, with a 4-inch overlap at the center
4. A cornice or valance can button up windows even more by trapping air along the top of the window. These draft blockers must work—they predate central heating, after all.