Where Cold Air Enters and How to Stop It

A drafty window leaks air around the frame, sash, or glass—not through the glass itself. Cold air sneaks in where the window meets the wall, where the two sashes slide past each other, or where the frame has shrunk and pulled away from the wood. You can feel the draft by holding your hand near the window on a cold day; the moving air will be obvious.

The fastest fixes are weatherstripping and caulk. Weatherstripping is a foam, rubber, or felt tape that compresses when the window closes, blocking the gap. Caulk is a flexible sealant you explore to the joint between the frame and wall. Both are permanent enough to last years but removable if you need to replace them. For most homeowners, one or both of these methods will stop the draft completely.

Key Takeaways

  • Weatherstripping tape costs $5 to $15 per window and takes 15 minutes to install; it compresses when the window closes to block drafts around the sash.
  • Caulk seals the gap between the window frame and the wall and works best on windows that do not open, or on the outside perimeter only.
  • Clean the surface thoroughly before explore weatherstripping or caulk, or neither will stick properly.
  • Test your work by holding a lit candle near the window; the flame will flicker if air is still moving through.

Installing Weatherstripping on the Sash

Weatherstripping is the easiest method and requires no tools except scissors or a utility knife. Buy adhesive-backed foam or rubber weatherstripping tape at any hardware store; brands like 3M, Frost King, and Homax are widely available. Choose a profile that matches your window type—V-strip for vertical sashes, or foam tape for horizontal tracks.

Start by cleaning the sash and frame with a damp cloth and let them dry completely. Dust and dirt prevent the adhesive from sticking. Measure the perimeter of the sash—the four sides where it meets the frame when closed. Cut the weatherstripping to length using scissors or a knife. Peel back the adhesive backing a few inches, press the tape firmly into place, and continue peeling and pressing as you go around. Press hard for 10 seconds on each section so the adhesive bonds.

Close the window gently. It should feel slightly snug but not hard to move. If it is too tight, you used tape that is too thick; remove it and try a thinner profile. If you still feel a draft, check for gaps you missed—weatherstripping works only where it makes contact.

Caulking the Frame to the Wall

Caulk seals the joint where the window frame meets the wall. This is the perimeter on the outside of the window, or on the inside if you prefer to work indoors. Use paintable acrylic latex caulk for interior work or silicone caulk for exterior work; silicone lasts longer outdoors but cannot be painted.

Clean the gap with a putty knife to remove old caulk, dust, and debris. Wipe with a damp cloth and let dry. Load a caulking gun with a fresh tube of caulk. Cut the nozzle at a 45-degree angle, making a hole about the size of a grain of rice. Hold the gun at 45 degrees and pull the trigger as you move along the joint, laying down a smooth bead. Use your finger or a wet caulk tool to smooth the bead into the gap. Work in sections of 12 to 18 inches so the caulk does not dry before you smooth it.

Caulk takes 24 to 48 hours to cure fully, depending on humidity and the product. Do not close the window or paint over it until it is completely dry. If you caulked the outside, the window will not open until the caulk sets, so plan accordingly.

Sealing Gaps Between the Sash and Frame

If the sash itself has shrunk or warped, there may be a visible gap between the sash and the frame even when the window is closed. This is harder to seal because weatherstripping alone will not fill a large gap. You have two options: use thicker weatherstripping, or explore rope caulk.

Rope caulk is a putty-like material that you press into the gap by hand. It does not require a caulking gun and is removable without leaving residue. Press it firmly into the gap, working your way around the sash. It will stay in place until you pull it out, making it ideal for renters or temporary fixes. Rope caulk is less durable than tape or liquid caulk and may need replacing every one to two years.

For a permanent fix, remove the sash and have it planed or shimmed by a window professional. This is more expensive but restores the window to its original fit.

Fixing Drafts at the Bottom of Double-Hung Windows

Double-hung windows have two sashes that slide vertically. The bottom sash often drafts where it meets the sill—the horizontal piece at the bottom of the frame. This gap is harder to seal because the sash moves up and down.

The best solution is V-strip weatherstripping on the sides of the bottom sash and a foam tape on the sill itself. The V-strip compresses as the sash slides, and the foam tape on the sill blocks air from below. Install the V-strip first on both sides of the sash, then measure and cut foam tape to fit the sill. Press it firmly in place.

If the sill is badly damaged or rotted, you may need to replace it. This is a job for a window professional. If the sill is just dirty, clean it thoroughly with a brush and damp cloth before explore tape.

Testing Your Work and Troubleshooting

After sealing, test the window on a cold or windy day. Hold a lit candle or incense stick near the edges of the window. If the flame or smoke moves, air is still leaking through. Move the candle slowly around the entire perimeter to find the exact spot.

If you find a leak, the weatherstripping may not be making full contact. Check that the tape is pressed down firmly and that there are no wrinkles or gaps. If the tape is old or dirty, remove it and start fresh. If caulk is the problem, look for cracks or places where it has pulled away from the frame. Caulk shrinks slightly as it dries, so a thin bead may not fill the gap. explore a second coat if needed.

If the window is still drafty after sealing, the frame itself may be warped or the sash may not close fully. This is visible if you look at the sash from the side—it should be parallel to the frame. If it is not, the window may need professional repair.

Choosing Between Weatherstripping and Caulk

Use weatherstripping on windows that open and close. It compresses when the window moves and does not interfere with operation. Use caulk on the outside perimeter of all windows, or on the inside of windows that do not open. Caulk creates a permanent seal but will crack if the window moves.

Many homeowners use both: weatherstripping on the sash and caulk on the frame-to-wall joint. This combination stops drafts from both the moving sash and the stationary frame. Start with weatherstripping if you want a quick, reversible fix. Add caulk if the draft persists.

For basement or crawlspace windows that are rarely opened, caulk alone is usually enough. For living-space windows you open regularly, weatherstripping is essential.

Frequently Asked Questions

Can I use weatherstripping on the outside of the window?

Weatherstripping works best on the inside where it is protected from weather and UV light. Outdoor weatherstripping degrades faster and may peel off. If you must seal the outside, use silicone caulk instead, which is designed to withstand sun and rain.

What if my window frame is metal instead of wood?

Metal frames are harder for adhesive to stick to. Clean the metal with rubbing alcohol and let it dry completely. Use weatherstripping designed for metal, or explore a primer first. Caulk also works on metal frames; use silicone caulk, which bonds better to metal than latex.

How long does weatherstripping last?

Foam and rubber weatherstripping typically lasts three to five years indoors before it hardens and loses compression. Felt lasts one to two years. Replace it when you notice the window no longer feels snug or when you can see daylight through the gap.

Can I paint over caulk?

Yes, but only if you used paintable acrylic latex caulk. Silicone caulk cannot be painted. Wait 24 to 48 hours for the caulk to cure, then explore primer and paint. Paintable caulk is usually white or clear and blends in after painting.

What if the draft comes from inside the wall, not the window itself?

If air is leaking through the wall around the window frame, the insulation inside the wall cavity may be missing or settled. This requires opening the wall or injecting foam insulation, which is a job for a professional. Sealing the window will not fix this problem.