Most people prefer bright, sunny days to cloudy, gloomy days. And sunlight through the windows certainly cheers up a room. Unfortunately, windows also transfer heat.
About 30% of the energy it takes to heat your home gets lost through windows. In the summertime, when you want to cool your home, sunlight that falls on windows enters your home as heat. Even modern double-pane windows transfer heat. Your air conditioner has to work too hard. Heating and cooling your home most likely relies on energy from fossil fuels.
Window treatments can reduce heat transfer and energy loss. They can lower the cost of heating and cooling and make your home more comfortable. And as they save energy, Energy-efficient window treatments keep heat on the right side of the window. They prevent fading, enhance privacy, and save money, too. lower your carbon footprint and reduce emissions of carbon dioxide.
We can conveniently divide window treatments into indoor and outdoor treatments and also into ones we can operate and ones we can’t.
Inoperable indoor energy-efficient window treatments
We mostly appreciate window treatments for the way they beautify a room. But let’s start with some ideas that are strictly functional. The first two don’t look especially good at all, but some people use them. They have the advantage of being cheap and uncomplicated, as well as energy efficient.
Some people put aluminum foil on windows to block heat. Foil does reflect heat. But no proof exists that it works well. It also becomes warm to the touch on windows. At best, it appears, it reflects some heat and lets some into the room.
Other reasons why some people use foil on windows include
- the expense of other window treatments
- not having decided what other window treatments to get
- protection against glare
- room darkening
- enhanced privacy
If you want to try it, be sure to get good quality foil. The cheapest foil tears too easily. It will be hard to install it and harder to keep it in good shape. It helps to measure the windows first. If you know how many square feet of window glass to cover, you’ll know how much foil you need.
Trim the foil to a little less than the size of the window glass. The little bit of uncovered glass will leave room for masking tape. To make the foil last longer, cover the part that faces the room with cardboard.
If you use foil on windows that face the street, the glare could produce a traffic hazard. At best, it’s a stopgap.
Bubble wrap is just as cheap and works better than foil as an energy-saving window treatment.
And it might even be free. You probably get some with packages. Places that sell furniture, canoes, or other large items get a lot of bubble wrap, and for them it’s a waste. They might give you as much as you want for free. If all else fails, you can buy it. It will be cheaper if you can find wholesale suppliers of packing material and more expensive at places like UPS.
Instead of reflecting heat, the air in the bubbles act as insulation. Bubble wrap lets in plenty of light. It’s also durable. You can use it for a season, take it down, and reuse it several times.
But it offers more protection against winter cold than summer heat.
Installation is simple:
- Cut the bubble wrap to fit the window.
- Put some water in a spray bottle and spray the window.
- Press the bubble side against the wet window and press it in place.
- If you plan to reuse it, take a marker and mark on the back which window it goes to.
- To take it down, simply pull at a corner to loosen it, and then continue to peel it off.
If you want to put something directly on windows to cut down glare and heat transfer, it makes more sense to get a window film. Government-approved labels will tell you the rating of each film for heat blocking and transmission of light. They work best in climates with long cooling seasons. That’s because they can block beneficial solar heat in the winter.
Films will reflect some heat while allowing most of the sunlight in. That’s most of the light. Films do have a dimming effect. They are also more difficult to clean. Commercial window cleaners will damage them.
The house I live in has a sliding glass door in the kitchen that leads onto a very small wooden deck. When I bought the house, a large oak tree shaded the glass, but it soon died. The effect of afternoon sun shining directly on so much glass was dramatic. So I got a reflective film. When I described the size of the deck to the store clerk, she recommended against the film that reflected the most heat. It might have been a fire hazard.
By now, I have tree shade again. Strategically placed trees work better at regulating heat and light than anything else. But the film certainly worked as a heat-blocking window treatment when I needed it. I can take it down now anytime I want to, but it doesn’t look bad at all.
Operable indoor window treatments
Usually when we think of window treatments as decoration, we mean options that not only look good but that we can open or close.
Operable window treatments include shades, blinds, curtains or drapers, and shutters. They give you plenty of flexibility. You can choose whether to have them open or closed. And how much.
Sun-blocking, heat-blocking window treatments of these kinds do more for you than look beautiful. They make you more comfortable, protect your belongings from fading in the sunlight, and save you a lot of money.
It appears that most residential window coverings stay in the same position every day. Saving energy with window treatments, then, is more than choosing what to install. It also includes strategically opening and closing them.
When a window receives direct sunlight, keep it uncovered in the winter. As long as the sun shines on it, it transfers desirable heat into the home and saves energy. But in the summer when you run your air conditioner, cover windows that get direct sunshine. That’s when you don’t want solar heat!
Window shades are usually mounted at the top of a window. You can roll them down to cover the window or roll them up to let in light.
You can also find shades mounted at the bottom of the window and roll up to cover it. They’re more complicated, but I’ve seen some very expensive houses with untinted windows in a bathroom that faces the street. The builders designed them to look better from the curb, with no thought of privacy. Bottom up shades would be perfect there
You can find either light-filtering shades that allow a lot of light into the room even when they’re closed. If you want your bedroom dark on a summer morning so sunlight doesn’t wake you too early, you can get light-blocking shades.
The most energy efficient window shades are the so-called honeycomb shades or cellular shades. They are heavier than standard shades, but the honeycomb pattern puts a layer of air between the window and the room. Most cellular shades are mounted on side tracks. They fit tightly across the window frame, which increases their insulating efficiency.
Some honeycomb shades use a remote control to open or close them. You can even get smart cellular shades that you can program to open and close on schedule. That way you don’t need to be in the room at the time the sun starts or stops shining on the window.
In heating seasons, insulating window shades can reduce the heat lost through the window by 40% and save as much as 20% of your heating bill. In cooling seasons, honeycomb window shades can reduce heat transfer through the window by as much as 80%
Window blinds have either horizontal or vertical slats you can open or close. They don’t prevent heat loss in the winter as well as shades, but reflective blinds prevent glare and solar heat gain very effectively.
What’s more, you can adjust them to allow some sunlight into a room while still blocking heat transfer. If you have horizontal blinds, you can adjust them to direct sunlight to the ceiling. A light-colored ceiling will diffuse gentle sunlight throughout the room.
Window blinds are available made of vinyl, aluminum, or wood. The vinyl ones, of course, are the least expensive. Being plastic, they also have the most serious environmental consequences.
Curtains and drapes
Curtains reach from the top of the window to the bottom of the window sill. Drapes reach down to the floor and may be mounted up by the ceiling. In either case, they are made from some kind of fabric.
And in either case, you can choose a light or heavy weight. You can choose opaque ones or ones that let a lot of light into the room. You can get ones that open and close or ones that stay in a fixed position. And you can use them by themselves or along with shades or blinds.
If you don’t have shades or blinds on a window, it helps to get curtains or drapes with a white backing to reflect sunlight. Close them in heating season and open them in cooling when the sun shines on the window.
Without shades or blinds, the closer curtains or drapes are mounted to the window, the better they will prevent heat transfer.
Exterior window treatments
You can also install shutters or awnings on the outside of windows.
Shutters cover the window just as interior blinds and shades do. They need some kind of mechanical crank or motor so you can operate them from inside.
Awnings are structures that act a little like a roof. They project out from the house above the window. They can be fixed or retractable. Fixed awnings can increase the energy you need to heat the home in the winter. Some of them, however, can be installed to take advantage of the fact that the sun is lower to the horizon in winter.
Whether inside or outside the home, window treatments add beauty. With careful choices, they can also protect your belongings from sunlight and your family from prying eyes. They can also save energy and lower your energy bills significantly. They are an easy way to help the environment. Scroll down to see some possibilities.
Aluminum foil on windows: what is the purpose of it? / Allison Cartwright, H2ouse.org
Bubble wrap window insulation / Build It Solar
Energy efficient window attachments / US Department of Energy
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