That’s because windows have an outsize impact on heat loss. “They aren’t as efficient as a wall,” says Michelle Blackston of the National Fenestration Rating Council, which sets efficiency ratings for products like windows, doors and skylights. Although windows amount to about 10 percent of a home’s surface area, heat transfer via windows can account for 30 percent of energy used for residential heating and cooling, according to the U.S. Energy Department.
Window treatments help reduce heat transfer, but not every room calls for the same product. A room drenched in sunlight, for example, requires something different than one shrouded in shade or in a cooler climate.
Before buying a new treatment, determine what conditions the windows typically experience, whether that’s hot summers, frigid winters or a combination of the two. Then head to the Attachments Energy Rating Council’s product database, which outlines different product models and their performance capabilities.
What if the product that would give your room the best efficiency bump doesn’t align with your design vision? Installing almost any treatment is better for reducing heat transfer than doing nothing, experts say, but consider pairing your preferred model with a more energy-efficient one to multiply the impact.
“The layered approach is best,” says Isfira Jensen, principal designer and chief executive of Nufacet Interiors, a residential luxury interiors firm in the New York City area. For example, she often combines cellular shades and drapery in her clients’ homes. “Not only is it a beautiful aesthetic, it also provides functionally a lot of energy efficiency as well.”
You’ll only reap the benefit of a lower utility bill if you correctly use your window treatments — meaning they ought to be adjusted as the day progresses. If you aren’t inclined to run around repositioning your shades as the sun moves across the sky, there are options for automatic or “smart” window treatments that do the work for you.
“There’s certain systems that are available today that you can set based on the sun that’s actually hitting the windows, you can set and change according to what your schedule is like,” in addition to weather settings and the sun’s projected rise and set times, says Tracy Christman, a product development and strategy executive with Budget Blinds. An added bonus? Auto-adjusting window treatments can give the impression that someone is home when you’re on vacation.
Not sure what type of window treatment will work best for you? Here is expert advice about what makes the most sense in different situations — and what to look for when shopping.
Shades can boost energy efficiency, but different styles excel at different tasks. Christman uses Roman shades in her Scottsdale, Ariz., home, which she says work well throughout the year in her temperature-fluctuating locale. During the hottest months, the shades keep the home “nice and cool,” she says, “but it also keeps it warm in the winter.”
The Energy Department notes that Roman and roller shades do the best job at blocking sunlight but only provide “a small amount of insulation” — a trade-off that might be worth it for a home that sees mostly hot days with occasional temperature drops.
Cellular shades, on the other hand, with their honeycomb-like fabric pockets that trap air, can maximize energy efficiency in both cool and hot climates. Specifically, the department says that cellular shades reduce window heat loss by at least 40 percent when the heat is running, and by 60 percent during the cooling season.
With any shades, Jensen favors thicker fabrics with tighter weaves to increase the insulation potential and minimize air circulation in the external fabric and the lining or backing.
Energy efficiency varies widely with drapery and curtains because they could be anything from light, airy sheers to sumptuous, velvety panels.
The upside to drapery, of course, is that it’s easy to change the look of a room by swapping out the panels, says Stephanie Harvey, who oversees energy efficiency programs at Hunter Douglas, a window coverings company.
“Oftentimes, we sell a lot of white and off-white in our shades and shadings, so I think drapery gives you that option to add color, to change more with your design, there’s just more trend and pattern and color options available,” she says.
If you go this route, more layers of lining, as well as thicker fabrics with tighter weaves, will prevent more heat transfer, whether you’re cranking the AC or turning up the heat. If your home doesn’t face strong sunlight or climate conditions, fabrics that are more breathable or see-through are an option.
“You can also not only line the drapery, but you can interline the drapery and an interlining will make that drapery thicker [and] it will also create more energy efficiency,” says Christman.
Shutters can both trap heat and prevent it from escaping, according to Christman. Jensen adds that she would consider them for clients that “feel like they need an added insulation factor or additional sun mitigating elements in the space.”
But from a design perspective, Jensen says shutters might not look natural on homes that aren’t in the farmhouse or coastal style. If you do opt for shutters, Jensen says, install them on smaller windows where the view won’t be disrupted, such as a sun-soaked kitchen facing a neighbor’s property.
While vertical and horizontal blinds may block the sun while drawn, they do “a poor job of preventing air circulation” no matter the material. In that regard, having blinds is almost like not having any window treatment at all, Jensen says.
And even if you don’t care about energy efficiency, Jensen says, it’s better to not use blinds. “They’re outdated, they don’t really look as good [as other options] … but beyond the aesthetics, they don’t really function as well as cellular shades or other products.”
Bridget Reed Morawski is a freelance writer in Washington, D.C.