BLINDS
Window blinds—vertical or horizontal slat-type—are more effective at reducing summer heat gain than winter heat loss.
INTERIOR BLINDS
Because of the numerous openings between the slats, it’s difficult to control heat loss through interior window blinds, but the slats offer flexibility in the summer. Unlike shades, you can adjust the slats to control light and ventilation. For example, when completely closed and lowered on a sunny window, highly reflective blinds can reduce heat gain by around 45%. They can also be adjusted to block and reflect direct sunlight onto a light-colored ceiling. A light-colored ceiling will diffuse the light without much heat or glare.
EXTERIOR BLINDS
Exterior roller blinds are usually made of wood, steel, aluminum, or vinyl. They are mounted above the window, and side channels guide them as they’re lowered and raised. When you lower these blinds completely, their slats meet and provide shade. If partially raised, the blinds allow some air and daylight to enter through windows.
DRAPERIES
A drapery’s ability to reduce heat loss and gain depends on several factors, including fabric type (closed or open weave) and color. With such a wide variety of draperies available, it’s difficult to generalize about their energy performance. During summer days, you should close draperies on windows receiving direct sunlight to prevent heat gain.
Studies demonstrate that medium-colored draperies with white-plastic backings can reduce heat gains by 33%. Draperies also stay cooler in the summer than some other window treatments because their pleats and folds lose heat through convection. When drawn during cold weather, most conventional draperies can reduce heat loss from a warm room up to 10%. Therefore, in winter, you should close all draperies at night, as well as draperies that don’t receive sunlight during the day.
To reduce heat exchange or convection, draperies should be hung as close to windows as possible. Also let them fall onto a windowsill or floor. For maximum effectiveness, you should install a cornice at the top of a drapery or place the drapery against the ceiling. Then seal the drapery at both sides and overlap it in the center. You can use Velcro or magnetic tape to attach drapes to the wall at the sides and bottom.
If you do these things, you may reduce heat loss up to 25%. Two draperies hung together will create a tighter air space than just one drapery. One advantage is that the room-side drapery will maintain around the same temperature as the interior space, adding to a room’s comfort.