How to Stop Drafts Under Doors and Windows This Winter

Under-door draft stopper fitted on the bottom of a door

When the temperature drops, a small gap under a door or around a window can make a whole room feel colder than the thermostat says. The good news: most drafts in a typical home can be found and blocked in an afternoon, with simple tools and no special skills. Here is a practical, step-by-step way to do it.

Step 1: Find where the cold air is getting in

Before you buy anything, spend 15 minutes locating the leaks. Pick a windy day if you can.

  • The hand test: Slowly move the back of your hand along the bottom of each exterior door, the door frame, and the edges of each window sash. Moving air feels noticeably cooler.
  • The light test: After dark, turn on a light on one side of a closed door and look from the other side. Light showing under or around the door means air can pass there too.
  • The paper test: Close a door or window on a sheet of paper. If it slides out with almost no resistance, the seal at that spot is weak.
  • The smoke test: Hold a lit incense stick near frames and sills (keep it away from curtains). If the smoke wavers or gets pulled sideways, you have found a draft.

Write down each spot and roughly how wide the gap looks. Gap size decides which fix will work best.

Step 2: Seal the gap under the door

The space between the bottom of a door and the floor or threshold is the most common draft source, and it is usually the easiest to fix.

  • Measure first. Measure the door width and the clearance between the door bottom and the floor at both ends. Floors are rarely perfectly level, so the gap can differ from side to side.
  • Removable fabric stopper: A draft stopper that slides onto the bottom of the door and moves with it is a good choice for renters, interior doors, or anyone who does not want to stick anything on.
  • Door bottom seal strip: A flexible strip attached along the bottom edge stays in place full time and covers the gap without anything lying on the floor.
  • Check the swing. After fitting either one, open and close the door several times. It should still close fully and not drag hard on rugs or the threshold.

Step 3: Seal around the door frame

If you felt air along the sides or top of the door, the weather stripping on the frame is worn, compressed, or missing.

  • Clean the frame stop with mild soap and water, then let it dry completely. Adhesive strips do not hold well on dusty or damp surfaces.
  • Choose a strip thickness that matches your gap. Too thin and air still passes; too thick and the door will be hard to latch.
  • Apply the strip in short sections, pressing firmly as you peel the backing. Cut it cleanly at the corners.
  • Close the door on a strip of paper again. It should now hold the paper with light resistance.

Step 4: Stop drafts around windows

Windows leak at the meeting point of the sashes, along the sill, and where the frame meets the wall.

  • Self-adhesive weather stripping works on the sash edges and window frames, the same way it does on doors.
  • Clear sealing tape can cover fine cracks around windows you will keep closed for the season. Test a small piece first, and peel it off gently in spring.
  • Heavy curtains drawn at night add another layer between you and cold glass.
  • Do not seal shut any window you might need as an emergency exit, especially in bedrooms.

Step 5: A few safety and comfort notes

  • Keep vents for furnaces, water heaters, fireplaces, and bathroom fans clear. Sealing drafts is about stopping unwanted leaks, not blocking needed airflow.
  • If you notice condensation building up after sealing a room, open a window briefly each day or run an exhaust fan.
  • Recheck your seals once mid-winter. Adhesive strips on high-traffic doors can loosen and may need a touch-up.

Quick winter draft checklist

  1. Find leaks with the hand, light, or paper test.
  2. Measure gap width and door clearance.
  3. Fit a draft stopper or bottom seal on each exterior door.
  4. Replace worn weather stripping on door frames.
  5. Seal window edges you will keep closed for the season.
  6. Keep appliance vents and emergency exits clear.

Helpful products

If you are putting together a draft kit this winter, these items from our store match the steps above. Check the product page for sizes before ordering. All ship free within the US.

A warm house in winter is mostly about the small gaps. Find them, measure them, and seal them one at a time.