How to Fix a Door That Lets in Draft

A drafty door is one of the biggest sources of energy loss in a home. Even a small gap around a door can let in significant cold air in winter and hot air in summer, raising your energy bills noticeably. Here's how to find and seal every draft.

How to Find Where the Draft Is Coming From

On a windy day or cold night, hold a lit candle or incense stick near the door edges. Watch for the flame or smoke to flicker — that's where air is getting in. Check all four sides: top, bottom, latch side, and hinge side.

Common Draft Locations and Fixes

Bottom of the Door (Most Common)

The gap under the door is the biggest source of drafts. Install a door sweep to seal it.

GroTheory Door Bottom Sweep 2-Pack (39") — seals drafts, noise, and insects; fits exterior and interior doors; easy screw-on installation

Sides and Top of the Door Frame

Worn or missing weatherstripping on the door stop lets air through the sides and top. Replace it with self-adhesive foam tape.

Foam Weather Stripping Seal Tape 16ft (1/2" x 1/4") — high-density foam, self-adhesive, soundproofing and insulation; apply to door stop where door contacts frame

Door Threshold Gap

If air comes in under the door even with a sweep, the threshold itself may be worn or misaligned. Replace or add a threshold seal.

Floor Transition Strip Self-Adhesive Threshold (3.3ft) — seals the gap between door bottom and floor surface

Step-by-Step Draft Sealing Process

Identify all draft locations with candle or incense test
Install door sweep on the bottom
Apply weatherstripping to all four sides of the door stop
Check and replace threshold seal if needed
Re-test with candle — no flicker means no draft

How Much Weatherstripping Do You Need?

A standard interior door (80" tall, 36" wide) needs approximately 16 feet of weatherstripping to seal all four sides. Buy a 16-foot roll to do the full door in one go.

Weatherstripping Types Compared

Foam tape: Easiest to install, good for irregular gaps, compresses over time
V-strip (tension seal): More durable, good for sides of door, harder to install
Door sweep: Best for bottom gap, most effective at blocking drafts
Rubber bulb seal: Most durable, best for exterior doors, requires stapling or nailing

Energy Savings

Properly sealing a drafty exterior door can reduce heating and cooling costs by 10–15%. A $20 door sweep and weatherstripping kit can save hundreds of dollars per year in energy costs.

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