I stood next to my front door one cold evening and felt a breeze. Inside the house. The gap at the bottom was wide enough to slide a pencil under. My heating bill that month was thirty dollars higher than the same month the year before.

Weatherstripping a door is the simplest home improvement you can do — it requires no tools beyond scissors, costs under fifteen dollars, and pays for itself in a single cold month. Here is how to do it right, not just slap on some foam tape and call it done.

Find the leaks first

On a windy day, hold a lit incense stick or a tissue near the edges of the door. If the smoke wavers or the tissue moves, air is getting through. Do this on all four sides — top, bottom, and both sides. Most doors leak at the bottom, but the top edge is a sneaky second. Pay attention to the hinge side — it often gets overlooked because you assume hinges create a seal. They do not.

Pick the right material for each gap

• Bottom gap: A door sweep. The kind that screws into the face of the door is more durable than the slide-on kind. Aluminum with a rubber fin lasts longer than plastic or brush-style sweeps. Measure the door width and cut the sweep to size with a hacksaw — the package will say “universal fit” but it is not.
• Sides and top: Adhesive-backed EPDM rubber weatherstrip, not foam. Foam compresses permanently within weeks and loses its seal. EPDM rubber springs back for years. It comes in rolls with different thicknesses — buy the one that matches your gap size.
• Irregular gaps: If the door is slightly warped or the frame is not perfectly square, use V-strip or tension-seal weatherstrip. It flexes to fill uneven gaps without requiring a perfect fit.

Installation

Clean the door frame with rubbing alcohol so the adhesive bonds properly. Dust and old paint residue will cause the strip to peel off in a week. Cut each piece slightly long and trim to fit — you cannot stretch weatherstripping. Apply it in a single continuous piece for each side to avoid gaps at seams.

For the door sweep: close the door, hold the sweep against the bottom so it just touches the threshold, mark the screw holes, drill pilot holes, and screw it in. Most sweeps have slotted holes so you can adjust the height. The sweep should make light contact with the threshold — too much pressure and the door is hard to open, too little and air still gets through.

Test your work

Close the door and look for daylight around the edges. No light should be visible. Run the incense test again. If air is still moving, check for gaps at the corners where strips meet — these need to be mitered or butted tightly. A tiny dab of clear silicone caulk seals any remaining corner gaps.