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Q: My apartment — on the 12th floor, with southeast exposure — is wonderfully sunny. Plants do well, and I enjoy the light and the view all day. However, the sun has bleached both wood and upholstered furniture and some carpet. I don't want to close the drapes and live in the dark. Can my windows be treated? Who does this work and what is the expected cost?

Bethesda

A: Having window film installed on the inside of your windows could be the solution. These films come with a wide variety of characteristics, enabling them to let certain wavelengths of light through while reflecting or absorbing other wavelengths.

Window film cannot totally prevent fading because other factors, such as humidity, account for about 5 percent of the problem. But depending on the window film you select, it can go a long way toward reducing the problem. All films block virtually all ultraviolet rays from the sun, which are responsible for about 45 percent of fading. Films also can block the rays that together cause about half of fading: visible light and infrared light, which causes heat.

Because you live in a tall building with many other units, begin by checking with the building managers about whether there are restrictions on window films. Some types make windows a lot more reflective on the outside. Some buildings have no rules on this, and let occupants decide how to treat their windows. Others want a uniform exterior appearance and rule out highly reflective films.

Once you know the rules, make an appointment to have a window film installer visit your apartment. Installers typically bring samples so you can see the differences in how the films affect your light and your view. Installers can also recommend suitable options if you have double-pane windows, because films that absorb infrared light can cause glass to heat up enough to break the seals or glass and void warranties. Be sure to ask the installer to leave you with a sample or two of films you like so you can check the effect in different conditions: sunny and cloudy and on different times of the day.

Before the visit, read up on the basics about window films. It will help you ask better questions and help keep you from wondering later whether you got an honest sales pitch. One good place to start is the Efficient Window Coverings website, efficientwindowcoverings.org, which allows you to compare the benefits of various window treatments — from films to drapes to awnings — and then drill down to the highest-rated products in each category. This website is focused on energy savings, which you didn’t mention as a prime consideration. But solving your fading issue can also save energy, so failing to factor that in would be shortsighted. And one benefit of using this website as a starting point is it doesn’t have a financial stake in its recommendations. It was developed by the Lawrence Berkeley National Laboratory in partnership with Building Green ( buildinggreen.com), a consulting and training company that began as the publisher of Environmental Building News, a newsletter that played a pivotal role in developing the green building movement.

This website uses the term “applied film” to distinguish the type of film you might want from “seasonal film,” which is the shrink-wrap-type plastic that people sometimes put up in the winter to cover drafty windows. Of all the many interior window treatments, applied film ranks highest if you select “view” and “visible transmittance” (i.e., the amount of visible light) as crucial factors and “solar heat control” and “glare control” as important ones.

For window-film manufacturers, the site lists only companies that meet two criteria. Their products must be tested according to standards from the National Fenestration Rating Council, the same industry group that ensures uniform comparisons of the energy issues related to windows. And the manufacturers must warranty their products for at least 10 years. The site says only three companies meet these standards — Johnson Window Films ( johnsonwindowfilms.com), Solar Gard ( solargard.com) and Solutia Performance Films, which recently became part of Eastman Chemical Co. ( eastman.com/pages/solutia.aspx). The manufacturers can point you to installers in your area.

Estimating the installed cost of window film is difficult without knowing all the specifics — the size of your windows, how high they reach up from the floor, and whether the glass consists of large panes or small panels. And, of course, the cost varies by the type of film you select. The sales manager at General Solar Co. in Gaithersburg (301-231-9500; generalsolar.net), which carries Eastman’s Llumar line of window films and others, said that for 100 square feet of windows, the cost of film and labor could run $9 to $24 a square foot. The Efficient Window Coverings website estimates costs based on a single window 30 inches wide by 60 inches tall at $80 for standard films and $125 for ones that let more visible light through while rejecting other wavelengths, such as infrared.

If you can afford it, professionally applied window film is definitely the way to go. The product selection and warranties are better, and there’s less risk of having hair, lint or other debris trapped between the film and the glass. But for people on a tight budget, especially for renters who aren’t sure how long they will stay, ­do-it-yourself installation is an option. Efficient Window Coverings estimates the DIY-installed cost for that ­
30-by-60-inch window at $10. DIY films include ones that are glued on via an adhesive backing and ones that grip the glass through static cling. Gila Platinum Heat-Control Window Film blocks UV, lets most visible light through, and cuts down on heat. It’s $37.97 for a 36-inch by 180-inch roll at Lowe’s). Gila is an Eastman brand, one of the companies recommended by Efficient Window Coverings, but in this DIY product it comes with a two-year warranty, including against breaking seals or glass in double-pane windows, provided the windows are still covered by the manufacturer’s warranty.