Thermal Drapes & Curtains
Thermal draperies are heavy fabric panels whose purpose is to trap heat. They share many of the same properties as black-out drapes though thermal drapes are usually heavier or at least the lining is heavier. Thermal draperies can trap heat to keep a room cool in the summer and warm in the winter. Another useful feature of thermal curtains is that they are also effective for reducing sound from outside.
The key for thermal drapes is to form a pocket of air between the window and the room. A single pane window has an insulation value of R-1. Double pane windows only take this up to R-2 or R-3. A heavy drapery can add an insulation R-value of up to R-7. That means it can be a much better investment to replace your curtains than to replace your windows when it comes to heating and cooling costs.
Thermal curtains are available as a product, but drapery liners are also available. You don't have to replace your curtains to get thermal insulation, you can just add a liner. However, liners may not be as effective as a regular thermal curtain because they may leave gaps for warm air to leak through.
On summer days, close drapes on windows receiving direct sunlight to reduce heat gain. A study by the University of Florida reported that medium-colored draperies with white plastic backings were found to reduce heat gain by up to 33%.
During cold winter weather, even conventional draperies can reduce heat loss by up to 10%. To maximize the benefit of thermal and standard draperies insulating abilities, close drapes tightly at night, and during the day for windows that do not receive direct sunlight.
The get the best results, draperies should be hung as close to windows as possible. Also let them make contact onto a windowsill or floor. The fewer gaps between the window and draperies, the better the insulation. For maximum effectiveness, you should install a cornice or valance over the top of a drapery or use draperies that extend to the ceiling. Also 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%. Overlapping two draperies, hung together, instead of just one, will create an even tighter air space.
Replacing standard curtains with thermal curtains, or just closing the gaps between your existing curtains and the wall will reduce drafts, lower your energy costs and keep you more comfortable. It is an easy project for a do-it-yourselfer and a simple way to cut energy costs.