Questions and Answers about Caulking and Weatherstripping Your Home

Reviewed and Revised on 10/10/2013 

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In a well-insulated home, air leaks are the greatest cause of wasted heating and cooling energy. Caulking and weatherstripping are effective ways to rid your home of costly drafts.

Questions and Answers about Caulking and Weatherstripping Your Home

In a well-insulated home, air leaks are the greatest cause of wasted heating and cooling energy. Caulking and weatherstripping are effective ways to rid your home of costly drafts. Keep in mind that heat always moves toward cold areas. Therefore, in hot, humid climates the biggest concern is hot air coming into air conditioned homes. However, during winter the opposite occurs – heated homes leak warm air to the outdoors through cracks and crevices.

How do I check a home for air leaks?

When looking for drafts around your windows, check the outside for any sign of caulking that has cracked or peeled. Check inside for leaks safely using a lit incense stick or a simple draft-checker, made with a piece of tissue paper or threads and a metal clothes hanger. On a windy day, move the draft-checker around windows, doors, electrical outlets, ceiling fixtures, attic hatches, and other locations where there is a possible air path to the outside. Air movement around these spots could mean there’s an air leak that may need caulking, sealing, or weatherstripping.

Infra red imaging can also be used to detect air leakages. 

This article by U.S. Department of Energy highlighting 19 spots/areas in a home which are generally leaky could be a good starting point for a homeowner.

Where should I caulk and seal?

Photo of a person caulking around a window

In addition to the window and door areas, you should caulk and seal air leaks where plumbing, ductwork, fans, or where electrical wiring penetrates through exterior walls, floors, and ceilings. This is a lot easier to do in new construction. Also with new construction, reduce exterior wall leaks by caulking or taping the joints if exterior sheathing is used.

With new or existing homes, install rubber gaskets behind outlet and switch plates on exterior walls. Inner walls may also need gaskets when the wall cavity is open, or air leaks into the attic from the wall cavity.

Use a paintable caulk to seal around the window frames and door frames where the interior frame meets the wall. On the exterior, seal around the window where the frame meets the siding. Do not seal the exterior window weep holes shut, as these allow any water or moisture that does get into the window area to get out. Because caulking is time consuming, use a high quality caulk or sealant suited to the materials and location. Caulks are available for higher temperature areas (e.g. chimneys). Caulks are used when the crack is less than ¼” wide. For cracks wider than ¼”, use materials suited for the area or gap such as metal, wood, rope caulk, backer rod, or other materials that will supply a base. Then caulk the area. 

When do my doors need weatherstripping?

Let’s look at an example. If you have a pair of 6′ 8″ exterior doors in your home that don’t have weatherstripping, you can easily have an opening of ¼” all along the edge where the doors meet. This ¼” gap adds up to a 20-square-inch opening to the outside. If you saw a hole this big in your wall, wouldn’t you want it fixed?

Weatherstripping around exterior doors can be checked with a flashlight. Outside the closed door, move the flashlight slowly around the door edge. If a helper inside the house can see light shining in, weatherstripping is needed.

Use quality weatherstripping that will last multiple years and that can be securely attached. Weatherstripping comes in various thicknesses, widths, and materials. Examples of materials and forms include spring or V metal, tubular gasket, foam-edge wood strips. Sponge and foam tape or felt are generally not as durable as silicone, metal, or vinyl weatherstripping.

Can I seal a gap under my door without replacing the door?

Yes. Door sweeps, thresholds, and door shoes are good ways to seal gaps under exterior doors. A door sweep (a strip of metal often with a flexible rubber or plastic edge), can be used on a door with no threshold. The sweep is connected to the door bottom, either inside or outside, depending on how the door moves. A gasket threshold replaces an existing threshold and can be attached to the floor directly under the door. This type of gasket wears quickly in high traffic areas. Door shoes have rubber or plastic gaskets set into a metal bracket. This shoe is affixed to the door bottom, and can be used with any threshold not worn in the middle. In addition, a draft stopper can be made out of fabric and sand into long tube to place in front of the door to stop drafts. For more information on weatherstripping and caulking, see Building America’s Home Air Sealing publication

Additional Sources of Information

Why Seal and Insulate ( 

National Renewable Energy Laboratory

University of Nebraska-Lincoln Extension