Q. A lot of heat and glare comes in my windows. It makes the air conditioner run more and us uncomfortable. I don’t want permanent window film because I want winter solar heating. What are my options?
A. Everybody knows the summer sun’s heat comes indoors through windows, but they often do not realize how much.
Not only do many windows have an insulating R-value that is only about one-tenth that of a wall, but they also allow the sun’s radiant heat in. This heating is significant and makes your air conditioner run much longer, using more electricity.
This also affects your electric rates. Utility companies have to invest millions of dollars extra to provide enough electric-generating capacity just for the peak afternoon demand. The rest of the time, it is not needed. By decreasing your afternoon air-conditioning load, this will help delay the need for new generating plants. This can minimize or delay rate increases.
Installing permanent window film is effective, but it cannot be removed for free passive solar winter heating. Some of the newer nearly clear low-emissivity permanent window films reduce summer heat gain and also reduce winter heat loss back outdoors. Even though they block some solar winter heat gain, they save overall.
Removable window film is another option. You can install it on your south- and west-facing windows in early spring and remove it in the fall. If you take care of it, it can be reused for many years and it will not lose its effectiveness.
Most removable window film adheres to the window glass by means of static cling. The natural properties of the tinted film, often vinyl, create a static charge to make it stick to the glass. This is similar to the film labels you see on new television or cell phone screens.
This film is often available in a bronze or smoke tint. It is best to install it on the indoor surface of the window glass.
Clean the window thoroughly and squeegee the film on the window while it is still wet. Because the film is tinted, do not use it on double-pane windows. In the direct sun, the absorbed heat may make the panes too hot and the seal between them may fail.
Another static-cling film option is film imprinted with stained or etched glass or floral patterns. These are attractive. Although the nearly clear etched-glass patterns do not block as much heat as tinted film, they do block some heat. They also reduce the sun’s fading ultraviolet rays coming through the glass.
Another option is a roll-up sun control shade. The most effective ones slide in vertical side tracks in the window opening. These can use special sun-control fabrics, screening or window film material.
Q. Our house is built into a hill for energy efficiency. This provides us with a daylight basement. We want to add air-conditioning to the basement, but do not want window units. What are our options?
A. Building a house into a hill, called earth-bermed, is energy efficient.
I am surprised your basement does not stay cool, but perhaps the sun warms it through the glass during the afternoon.
A minisplit ductless system is probably your best cooling option if you do not want a window unit. These systems have the cooling coils and blower mounted up on the wall. The outdoor compressor is connected to it with a small refrigerant tube and wiring.
