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Clearly Better Patio Doors

My old sliding glass patio door produces a draft and I can hear road noise through it. It sweats, doesn’t slide smoothly, and probably is not secure. What should I consider in a new one?—Ted K.

An old sliding glass patio door can be one of the biggest energy wasters in a home. Air leakage is often the worst culprit, even in summer when warm moist air leaks indoors.

A sliding glass door is basically a huge hole in the insulated walls of your house. Your old door may have an insulation level of R-2 at best. When you sit near the door at night, heat from your body radiates to the cold outdoors, causing you to feel colder than the room temperature. This can make you turn the thermostat up, wasting energy.

The highest energy-efficient glass for sliding doors is R-10. This super-efficient glass has triple panes, with low-emissivity (low-e) coatings on two of the glass surfaces with krypton gas between the panes. The krypton gas also reduces outdoor noise transmission.

The airtight seals are also better on the new doors. Keep in mind, a sliding glass door has a lot of mating joints that must be sealed with weatherstripping. Much of the joint’s area is a sliding seal, not compression as on a casement window or a hinged door. As your door ages, keep an eye on the weatherstripping and replace it when it is worn. The manufacturers offer replacement kits.

French-style patio doors are increasingly popular. These have wider rails and stiles on the door frame to simulate the appearance of double-hinged doors.

Sliding glass doors cover a large span, so the strength of the frame is critical. Typical material options are aluminum, fiberglass, vinyl, wood and vinyl, or aluminum-clad wood.

Fiberglass is one of the best low-maintenance materials for sliding glass door frames. I use this type in my home. The frames are made with a pultruded process, which is different from how fiberglass boat hulls and car bodies are produced. Pultrusion combines long glass fibers with strong resins to create an almost indestructible frame.

A fiberglass frame expands and contracts with temperature changes at a similar rate as the glass panes. This reduces stresses in the frame and along the seals where the glass panes rest in the frame. For a natural wood appearance, select one with a real oak veneer bonded over the indoor surface of the fiberglass frame.

Vinyl is another low-maintenance frame material. Its color goes completely through the frame, so it looks good even with small scratches. Look for fusion-welded corners, metal reinforcement inside the frame, and ball-bearing steel or nylon rollers. Vinyl or aluminum cladding over a wood frame minimizes outdoor maintenance. All-aluminum frames should have a plastic thermal break between the outdoor and indoor surfaces.

The type of glass is key to energy efficiency. The triple-pane R-10 glass may be outside the budget for many homeowners. As a minimum, select double-pane, low-e glass. For hot climates, you may prefer to have tinted panes. In very cold climates, the R-10 glass may make economic sense or choose less-expensive R-6 triple-pane glass.

There are several options that can make your sliding glass door more secure. Multipoint lock and foot lock features require a thief to take more time to pry the door open. If you are really concerned about security, select double swinging or tilt/turn (swings on hinges or tilts in at top for ventilation) doors. Some closely resemble sliders and they are more difficult to force open.

Write for Utility Bills Update No. 939, a buyer’s guide to patio door options. Include $3.00, a business-size SASE, and Update number. Mail requests and questions to James Dulley, Kentucky Living, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to to instantly download.

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