Window Treatments Can Help Cheat Outdoor Heat

If the summer swelter has you reaching for the "high" button on the fan or the air conditioner - or both - don't sweat it. Instead, give your windows a treatment.

Nearly 40 percent of unwanted heat in homes comes in through the windows, according to the Energy Efficiency and Renewable Energy Clearinghouse (EEREC), in Merrifield, Va. So, it follows that almost anything that blocks, reflects, or absorbs solar heat significantly lowers the sizzle factor.

Outside shading tends to be more effective than indoor shading, says Michael Lamb at EEREC, but you need to consider what will work best for you.

Will you want to open and close blinds daily or install something just for summer such as outdoor shutters? Can you do with less light and air flow? Do you want a filtered view or completely opaque privacy?

Outside options include awnings, overhangs, trellises, shutters, shades, and shade trees. Inside options include shutters, drapes, shades, and blinds.

Another option is to install high-performance windows or glass coatings, similar to tinted car windows. Sun-control films (also known as solar-control glazings, coatings, or "low-e" films) are applied to window glass. They filter sunlight, lower heat gain, and reduce glare. But most homeowners opt for removable barriers that allow more sunlight or privacy as needed and "dress up" a window.

The trade-off with any barrier, however, is that typically what you lose in heat, you also lose in light.

"One of the big reasons people want to block the light is not only heat control, but to stop furniture from fading," says Allan Blacker, owner of the Window Shoppe, in Newton, Mass. Some people want the all-or-nothing aspect of an up-down shade; others want Venetian or vertical blinds, or shutters that allow for more controlled lighting.

For the best of both worlds, he suggests sunscreens or sunshades, semitranslucent mesh shades made from nylon or fiberglass by Phifer. These are transparent and block ultraviolet rays (the ones that fade interiors) and heat.

Mr. Blacker also demonstrates Verosol shades, often described as the one-way mirror shade. You can see through the shade, but it has bonded aluminum (mylar) backing to reflect the sunlight on the other side.

The Silhouette Window Shade, made by Hunter Douglas, has a much softer look and acts as part curtain and part blind: Two pieces of gauzy crepe fabric surround adjustable stiff "fabric" vents.

At the store Windows Beautiful in Palm Bay, Fla., customers looking for ways to beat the heat often choose honeycomb shades. These are cellular shades that come in single, double, and triple-layer pleats, and act as insulators, trapping heat. (See photo.) They are also sold with reflective coatings that block light. Prices range from $80 to $360 per window.

Alternatively, shop owner Terry Van Valkenburg suggests double vertical blinds - slim panels that hang from an overhead runner. They may be more expensive, he says, but they pay for themselves in the long run because of their durability. A Luminet privacy sheer - chiffony curtain material pleated with adjustable privacy panels - will also knock out some sun.

"I do some awnings, but outdoors means more maintenance - sap, birds, weather, etc. And with those we find you still need some inside privacy," he says.

Interior plantation-style shutters, often made out of wood or vinyl, are effective because they close down so tight. Prices range from $25 (for a do-it-yourself kit) to $400 (for professional installation) per window.

What does Mr. Van Valkenburg use in his Florida home? Honeycomb shades for a house of 1,700-square-feet. His electric bills run $75 a month in summer.