What is weatherstripping?
Updated August 2026
Weatherstripping is the flexible seal that runs around the moving edge of a door or window and squeezes shut when that door or sash closes. It shows up in five common forms: adhesive foam tape, hollow rubber or silicone bulb gasket, felt, springy metal or vinyl V-strip (also sold as tension seal), and the sweep screwed along the bottom of a door slab. Caulk and weatherstripping are not interchangeable. Caulk seals joints that never move, such as a window frame against siding. Weatherstripping seals joints that open and close thousands of times a year.
Where it is
On an exterior door, look for a strip in the jamb along both sides and the head, a gasket in the threshold, and a sweep on the bottom edge of the slab. Double-hung windows carry V-strip in the side channels plus a strip at the meeting rail where the two sashes overlap; sliding patio doors use brush pile instead. The forgotten locations are the attic hatch, the door between the house and an attached garage, and the crawl space access panel. Two fast tests: close a dollar bill in the door and pull, and if it slides free with no drag the seal is not compressing; or run the back of a wet hand around the perimeter on a windy day.
What it does
The strip has one job: keep conditioned air from walking out around the opening while blocking wind-driven rain, dust, and insects on the way in. The U.S. Department of Energy puts the savings from air sealing plus attic insulation at roughly 15% of heating and cooling costs, and door and window perimeters are the cheapest slice of that leak budget to close. Worn weatherstripping announces itself. Foam goes hard and crumbles under a thumbnail, felt mats flat, a bulb gasket splits on the strike side, and a sweep wears to a stub until daylight shows in the bottom corner. Whistling during a storm, frost on the inside edge of a steel door, and a dust line across the threshold all point at the same failure.
Maintenance
Walk every exterior door and operable window twice a year, at the spring and fall HVAC changeover. Adhesive foam needs replacing about every 2–3 years, felt every 3–5 years, and kerf-in bulb gasket or metal V-strip every 8–10 years. Doing the whole house in one pass beats chasing one draft at a time: the replacement schedule by material sorts out which strips are due, and the door swap walkthrough covers the 20-minute version. Put the inspection on your seasonal checklist so the drafty door gets fixed in October instead of February.
What it costs to replace
A replacement weatherstripping runs $10–30 per door in materials, or $75–150 per door if a handyman does it.
OnOtto's photo scan identifies parts like this in your home and builds the maintenance schedule for you. See how the scan works.
Frequently asked questions
How much does new weatherstripping actually save?
Do the arithmetic on the gap. A 1/8-inch space under a 36-inch door is a 4.5 square inch hole in your wall, open all winter, and the gaps along the two jambs usually add as much again. Sealing one bad exterior door typically trims $30–80 a year off heating and cooling in a cold climate, so a $15 kit earns its money back in the first season. Price the rest of the shell work with the cost calculator.
What kind of weatherstripping should I buy?
Match the material to the joint. Adhesive foam tape is fine on an attic hatch or a door nobody uses, but it flattens fast under traffic. Metal or vinyl V-strip is the durable pick for double-hung window channels and door jambs because it hides in the gap and adjusts itself. Kerf-in silicone bulb gasket gives the tightest seal on a modern prehung door, and silicone stays pliable below freezing where vinyl stiffens. Use a sweep or an automatic door bottom for the gap under the slab.
My door still leaks after new weatherstripping. Why?
New seal, wrong geometry. If the gap is wider at the top than the bottom, the door is out of square or the hinges have sagged: drive 3-inch screws through the top hinge into the framing, or shift the strike plate 1/16 inch. A leak only along the bottom usually means the threshold needs its adjustment screws raised until the sweep just kisses it. A slab bowed more than 1/4 inch will not seal against any gasket and needs replacing.
When is the best time of year to replace weatherstripping?
Early fall, before the first hard freeze. Adhesive-backed foam and butyl tape need a surface above about 50°F to bond, and they peel within weeks if you press them onto a cold jamb in January. Fall also groups the job with the rest of the exterior shell work: the chimney cap, the gutters, the crawl space vents. If you find a failed seal mid-winter, screw on a metal V-strip or a bronze sweep rather than tape, then redo it properly in spring.