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Window basics

Choosing windows used to be a matter of deciding on double-hung, fixed, or casement windows. Now you’re faced with U-factors (heat loss), SHGC (solar heat gain coefficient), VT (visible transmittance), argon, and krypton. When buying windows, consider the following:

• Without any bells and whistles, the insulating value of a double-glazed window is about one-third greater than that of a single-glazed window.

• A low-E coating is a microscopic layer of metal on the inside face of the glass that reduces heat transmission. Because it also reflects incoming light and the resulting solar heat, manufacturers have developed low-E coatings for high, low, or moderate solar gain.

• Sealing a gas between the layers reduces heat flow even more. Argon is efficient and cheap. Krypton is a better insulator, but more expensive.

• Frames can be made of wood, hardboard, aluminum, or vinyl. Wood is strong and light but needs maintenance, as does hardboard. Aluminum is an ineffective insulator, but frames with added foam core work well. Vinyl is maintenance-free and somewhat of an insulator.

FOLLOW THE ENERGY STAR. So now what? Look for an Energy Star sticker, which lists government performance standards for each of three climate zones: Northern, where heating is a primary energy concern; Central, where heating and cooling are both concerns; and Southern, where cooling is the major concern. Energy Star labels rate windows for efficiency. Ratings are based on the following:

• U-factor is the rate of heat loss. The lower the U-factor, the better a window insulates.

• SHGC stands for solar heat gain coefficient. It’s rated on a scale of 0 to 1 and the lower the number, the less solar heat the window transmits. People living at the equator would prefer a lower number.

• VT stands for visible transmission—the amount of light that gets through—and is rated on a scale of 0 to 1. The higher the number, the more light you’ll have.

• AL stands for air leakage, a measure of how much air slips past the weather stripping. The lower the leakage, the better the window, but manufacturers say leakage is not as important a concern as U-factor or SHGC.

Once you know the standards and what they mean, look at the Energy Performance section of the label. Compare the factors you think are important with what the manufacturer says the window does. If you’re wondering if this research is worth the work, consider this: Top-notch windows can cut a Boston homeowner’s heating bill by 30 to 40 percent. An Albuquerque homeowner can save between 6 and 32 percent in air-conditioning costs.

Window maintenance tips

Cleaning And Lubricating

CLEAN THE TRACKS ON WINDOWS AND DOORS WITH A HAND VACUUM AND A TOOTHBRUSH TO KEEP THEM OPERATING SMOOTHLY. Dirt buildup is particularly a problem on storm window tracks. Aluminum and vinyl tracks can be washed with soap and water.

ONCE THE WINDOW TRACK IS CLEAN, COAT IT WITH WAX OR SOAP. Wax, being waterproof, will last longer. For windows with metal edges that run on metal tracks, you'll find a variety of lubricants: penetrating oils, silicone sprays, and powdered graphite. Some cleaners containing solvents may damage vinyl-clad windows; test them on a hidden part of the window first.

CLEAN WEATHER STRIPPING BY SPRAYING IT WITH A HOUSEHOLD CLEANER AND WIPING AWAY THE DIRT. Soap will wash paint off vinyl weather stripping, metal, or plastic runners. If paint is causing the edge of a wooden window to bind, you will have to remove the window and sand it smooth.

Adjusting springs - Newer aluminum or vinyl windows have spiral counterbalances to keep them from crashing down when open. You can adjust the spring tension by turning screws in the track insert. Adjust until the window travels easily but won't slip down when put in place.

Freeing A Stuck Window

IF A WINDOW IS PAINTED SHUT, YOU CAN OFTEN BREAK THE PAINT FILM by putting a block of wood against both the sash and the stop. Strike the block with a hammer in the direction of the stop to free the window.

IF A HAMMER AND BLOCK OF WOOD WON’T BREAK THE PAINT FILM, cut the film with a tool known variously as a sash saw, window opener, or paint zipper. Put the teeth into the crack between the window stop and sash, and slide it along the sash to cut the paint.

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