Weatherstripping which blocks drafts around doors and windows won't save much energy. Recent studies have shown that such drafts actually contribute little to overall heat loss. Still, weatherstripping will do a lot to make the house feel more comfortable. That may save some energy indirectly, since you may not need to turn up the thermostat as much if the room isn't drafty.
Weatherstripping comes in a wide variety of designs and materials: foam or rubber tapes, plain or reinforced with a strip of wood; a tubular plastic gasket, plain or reinforced; felt, plain or reinforced; and springy strips of plastic or metal. You should buy weatherstripping by type, not by brand. It should be easy to cut and form to the proper size and shape, and easy to secure to a flat surface. It should be resilient enough to seal even after it's been crushed or rubbed thousands of times. It must be able to survive extremes of heat, cold, and humidity. It also should interfere as little as possible with the movement of a door or window.
This is a key test; the ability to impede airflow in the equivalent of a 50-mph wind. Two types work well--closed-cell foam with rubber tapes, and strips with a tight-sealing, rigid gasket. Reinforced felt and open-cell foam tape are much less effective. Inch for inch, reinforced felt allows more than 250 times as much air to leak through as closed-cell foam.
Most types of stripping held up well enough through 600 hours of test. Plastic and bronze tension seals, felts, and silicone gaskets hold up well. The worst, open-cell foam tape, becomes dry, brittle, and powdery. Whatever material it is made of, weatherstripping works by plugging and sealing a gap between moving surfaces. Some types work well on both doors and windows, while others are more limited. Here is a rundown on the types you'll see in the stores:
Tape - EPDM (ethylene-propylenediene monomer) rubber, non-porous, closed-cell foam, open-cell foam, and sponge rubber. You can buy rolls of tape in various widths and thicknesses. The tape is self-adhesive and thus extremely easy to install. The tape is cut to length with scissors; the backing peeled away and stuck in place.
Best uses: Along a doorjamb or at the top and bottom of a window sash. It is not well suited for a window jamb, although some manufacturers' literature list this usage. Tape's size and flexibility make it well suited for blocking an irregular crack. Tape that is rectangular in cross-section is well suited for sealing corners. Tape works best when it is compressed.
Reinforced foam - Closed-cell foam tape attached to a strip of wood molding.
Best uses: Nailed in place around a window or doorjamb. Reinforced foam can be a bother to install because it must be sawed, nailed, and painted.
Tension seal - A self-stick strip of plastic that is folded along its length to form a V, or a springy bronze strip that is shaped to bridge the gap between, for example, a window sash and its frame. The shape of the material creates a seal by pressing against the sides of a crack to block drafts.
Best uses: Inside the track of a double-hung window or between a door and its jamb. Plastic V strips are easier to install than bronze; the latter must be nailed and formed in place. Either type of tension seal can be difficult to install in a corner since the strips must be mitered so they will join tightly. One variant design we encountered, which combined a V-shaped gasket of vinyl-clad foam and wood reinforcement, sealed well enough but was fairly difficult to install.
Felt. - Plain or reinforced with a flexible metal strip; sold in rolls that must be cut to length and stapled or tacked into place. Felt seals best if the staples are positioned parallel to the length of the strip.
Best uses: Plain felt can be fitted in a doorjamb so that the door presses against it. Reinforced felt can seal around a door or a window.
Pile - A narrow strip of furry, carpetlike material with a rigid back. Some versions come with an adhesive backing.
Best uses: Fitted in recessed slots around the perimeter of a window sash, storm door, or sliding glass patio door.
Tubular rubber and vinyl - Tubes of sponge rubber or vinyl with a flange along their length that is stapled or tacked into place. These gaskets work when a door or window presses against them to form a seal. They are not as easy to install as self-stick types.
Best uses: Around a door.
Reinforced silicone - A tubular gasket attached to a metal strip similar in appearance to reinforced tubular vinyl. It seals well, but it can be hard to install. You must hacksaw the metal strip to size. Also, butting two pieces tightly in a corner can be tricky. (This product may be easier to find in a contractors' supply store than in a hardware store.)
Best uses: On a doorjamb or window stop.
Door seals - Vinyl door seals with multiple sealing edges of equal length are better than felt and brush seals.
Best uses: To seal the space beneath a door.
No single type of weatherstripping works well everywhere. You will probably need one type for doors, another for windows. The descriptions on the preceding pages can help you decide which type is best to use for each specific purpose. Product packaging also gives recommendations for use.
Self-stick tapes probably have the widest range of uses. They are also the easiest type to install and provide the best seal. However, they do not last very long. To block drafts around double-hung windows, use a plastic V-strip or a bronze tension seal in the space between the window sash and the frame.
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