Q - I want to reduce the sun's heat and fading rays through my windows, but I often open them for natural ventilation. What can I use to block the sun's rays both when the windows are opened and closed? W. L.
A - Since you plan to open your windows at times and run your air conditioner less, special new sun control screens are probably your best choice. Window film applied directly to the glass is effective, but it won't block the sun through the portion of the window that is open.There are several new types of sun-control screening. In addition to stopping insects, these can block up to 80 percent of the sun's heat, glare and ultraviolet rays. Therefore, your curtains, carpets and furniture will fade much less.
One type of sun-control fiberglass screen uses a fairly dense weave and is available in many light and dark colors. You can install it in your existing screen frames or have it professionally installed. One new screen design also uses a simple tension system to hold the screen very taut.
Sun-control screens also offer privacy. Although you can clearly see out through it, the view indoors from the street is somewhat impeded.
It is most effective to have full window screens. You can make inexpensive frames yourself to fit your windows. If you plan to use only half screens, like on a double-hung window, you might want to install sun-control window film on the top half of the window that stays closed.
The newest and most effective type of sun-control screen is made of extremely tiny aluminum louvers, only about 1/20 of an inch wide. Because they are so narrow and spaced more than 17 to the vertical inch, it is difficult to notice that it is actually many tiny louvers.
Each tiny louver is tilted at 17 degrees, the best angle for blocking the sun's heat and fading rays throughout the daytime. From indoors, the view is very open and clear, especially if you look out to see small children.
This design provides 70 percent to 80 percent open area, so you get excellent ventilation. There are very narrow vertical ribs to support the louvers.
Before you purchase any screens to be used for sun control, compare the performance specifications. The shading coefficient is the most common specification you will find. A lower shading coefficient (for example .26 vs. .49) means it blocks more of the sun's heat.
You can write to me for UTILITY BILLS UPDATE No. 304 showing a list of manufacturers of various types of sun-control window screens, performance specifications showing the heat blocking properties, and a small sample of fiberglass screen. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, Ohio 45244. Please include $1.00 and a self-addressed business-sized envelope.
Q - I heard that a central air conditioner runs more efficiently when the air is cooler around it. Would it help to spray a fine mist of water on the condenser coils to keep it cooler? H. W.
A - When the outdoor air around the condenser coils is cooler, an air conditioner runs more efficiently. It is easier for it to give off the heat to cooler air. Some people have designed systems to spray water on the coils. This cools the coils by evaporation of the water.
You should definitely consult your air conditioner contractor or service technician before attempting this. The water may cause deposits on the coils and the constant spray may hasten corrosion of the unit. Also, it may drop the temperature of the coils below the design temperature.