By James Dulley, Published November 04 2011
Sensible Home: Windows, shades, film can improve efficiency
– Mona J.
Dear Mona: People most often think about the energy loss during winter (and heat gain during summer) from windows, but as you mentioned, comfort is also an important concern. Even if your house air temperature is comfortably warm, you may still feel chilly sitting near a window.
This chilly phenomenon is caused by radiant heat loss from your skin to the cold window glass. Reducing the difference between your skin temperature and the glass or shade temperature can cut the radiant heat loss by 16 times.
There are several options to improve the efficiency of windows and your comfort – new windows, shades or window film. Although installing new windows is the most expensive option, if your existing windows are leaky and the frames are deteriorated, this is really your only option.
If your existing windows are inefficient,
but in good condition, then improving them with shades or window film can be an effective alternative. The best shades increase the insulation value by R-6. Applying low-emissivity window film does not increase the insulation as much, but it does not block the outdoor view.
I installed Warm Window (R-6 insulation) shades in my own home/office and have tested them for two years. Since my computer is right next to a window, comfort was also an issue for me. Even though I already have efficient double-pane, low-emissivity windows, I feel the difference. I also close them sometimes during summer to block the sun’s heat and for privacy.
When you select insulating window shades for your windows, consider the insulation value and how well they seal along the sides and the bottom. The air in the gap between the window and the shade will get cold and tend to settle downward. If the seal is not good, cold air will leak out. Having an airtight film in between the shade’s multiple insulating layers is a plus.
Look for shades with deep vertical side tracks to seal well against the edges of the shade material, which slides up and down in the tracks. Some type of foam or brush weatherstripping along the bottom of the shade should conform and seal well on the windowsill even if it is not perfectly level.
The smoothness of operation is important because, if they are difficult to open and close, you will not use them as often as you should. Roman shade styles are the easiest to operate and to make yourself as thick (for insulation) as you like. Double-cell pleated shades with dead air spaces are also effective and allow filtered light through.
The following companies offer insulating shades: Country Curtains, (800) 937-1237, www.countrycurtains.com; Cozy Curtains, (800) 342-9955, www.cozycurtains.com; and Smith and Noble, (800) 560-0027, www.smithandnoble.com; Symphony Shades, (877) 966-3678, www.cellularwindow
shades.com; and Warm Company, (800) 234-9276, www.warmcompany.com.
Send inquiries to James Dulley, The Forum of Fargo-Moorhead, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit www.dulley.com.