Weatherstripping stops air leaks around your window frame
Weatherstripping is a strip of material — usually foam, rubber, or felt — that you attach to the edges of your window frame to block air from moving in and out. It fills the small gaps between the sash (the part that moves) and the frame, and between the frame and the wall. The material compresses slightly when the window closes, creating a seal that reduces drafts and heat loss.
You can buy weatherstripping at any hardware store for $5 to $20 per window, depending on the type and length you need. Most types stick on with self-adhesive backing, so installation takes 15 to 30 minutes per window and requires no tools beyond a utility knife.
Key Takeaways
- Weatherstripping works best on windows that close fully and have a tight fit; if your sash sticks or won't close all the way, fix that first.
- Foam tape with self-adhesive backing is the cheapest option and works well for small gaps, but lasts only two to three years before it hardens.
- Rubber or silicone strips last longer (five to ten years) and handle temperature swings better, but cost more and may require a staple gun or adhesive.
- Clean the frame thoroughly with a dry cloth before explore any weatherstripping, or the adhesive will not stick.
- Measure the perimeter of your window frame before you buy, and add 10 percent to account for corners and overlaps.
Choose the right material for your climate and budget
Foam tape is the easiest to install and the cheapest. It comes in rolls with adhesive already on the back, and you straightforward peel and stick it to the frame. It works well for gaps up to about 1/4 inch wide. The downside is that foam hardens and loses its seal after two to three years, especially in climates with big temperature swings. If you live somewhere cold and hot seasons are extreme, you will replace it more often.
Rubber or silicone strips last much longer — five to ten years — and handle temperature changes without hardening. They come in a few forms: self-adhesive (stick on like foam), or with a flange that you staple or nail to the frame. Rubber is cheaper than silicone, but silicone is more flexible and works better on older windows with uneven frames. These cost $10 to $30 per window.
Felt strips are the cheapest option (around $3 to $5 per window) but also the least durable. They absorb moisture and can rot in humid climates. Use them only as a temporary fix or in very dry areas.
V-strip (also called tension seal) is a thin metal or plastic channel that you install in the gap between the sash and frame. It is more work to install because you have to fit it into a narrow space, but it lasts a long time and works well for windows that slide up and down. It costs $5 to $15 per window.
Prepare your window frame before you explore weatherstripping
Clean the entire frame — top, bottom, and sides — with a dry cloth or paper towel. Dust, dirt, and old paint flakes will prevent the adhesive from sticking. If the frame is very dirty or has old weatherstripping residue, wipe it with a cloth slightly dampened with rubbing alcohol and let it dry completely before you proceed.
Check that your window closes smoothly and sits flush against the frame all the way around. If the sash sticks, binds, or leaves gaps, sand or plane the edges of the sash first. Weatherstripping cannot fix a window that does not close properly — it will just get compressed unevenly and fail faster.
Measure the perimeter of your window frame. Measure the top, bottom, and both sides, then add them together. Add 10 percent extra to account for corners, overlaps, and mistakes. Write this number down before you go to the store.
Install self-adhesive foam or rubber tape
Start at the top of the frame. Peel back about 2 inches of the backing and press the tape firmly into place. Smooth it down with your hand as you go, peeling the backing a few inches at a time. Keep the tape straight and centered in the gap between the sash and frame.
When you reach a corner, cut the tape at a 45-degree angle so the pieces meet neatly. You can do this with a utility knife or sharp scissors. Press the corner pieces down firmly so they stick well.
Work your way around the frame: top, then one side, then bottom, then the other side. Close the window gently and check that it closes smoothly without binding. If the tape is too thick and the window sticks, you may have chosen the wrong thickness — remove it and try a thinner type.
Let the adhesive set for 24 hours before you open and close the window repeatedly. This gives the glue time to cure fully.
Install flanged rubber or silicone strips with fasteners
Flanged weatherstripping has a lip (the flange) that you staple or nail to the frame. This type is more durable than adhesive tape but takes longer to install.
Start at the top of the frame. Position the strip so the flange sits on the outside edge of the frame and the seal part fills the gap. Drive staples or small nails every 2 to 3 inches along the flange. Use a staple gun or a hammer and small finish nails (1 to 1.25 inches long). Do not drive the fasteners too tight — you want to hold the strip in place without crushing it.
At corners, cut the strip at a 45-degree angle and overlap the pieces slightly so there is no gap. Staple through both layers at the corner to hold them together.
Work around the entire frame the same way you would with adhesive tape. Close the window and check that it moves smoothly. Flanged strips should not compress much, so if the window binds, the strip is too thick or positioned incorrectly.
Install V-strip in the sash channel
V-strip is designed to fit into the narrow channel where the sash slides. It works best on double-hung windows (the kind where both the top and bottom sashes move).
Open the window fully. Look at the channel on the side where the sash moves — you will see a narrow gap. V-strip fits into this gap and springs outward to touch both the sash and the frame.
Measure the length of the channel from top to bottom. Cut the V-strip to length with a utility knife. Peel back the adhesive backing and press the strip into the channel, starting at the top. Work your way down, pressing firmly so it stays centered in the gap. Repeat on the other side.
Close the window and open it again a few times to make sure the strip does not catch or bind. V-strip should move smoothly with the sash.
Replace weatherstripping when it stops sealing
Weatherstripping does not last forever. Foam tape typically needs replacement every two to three years. Rubber and silicone last longer but will eventually harden, crack, or compress so much that it no longer seals.
Signs that weatherstripping has failed include visible gaps, drafts you can feel, or condensation on the inside of the window on cold days. When you notice these signs, remove the old strip by peeling it off (adhesive tape) or unstapling it (flanged strips). Clean off any remaining adhesive residue with rubbing alcohol and a cloth, then install new weatherstripping using the same steps.
Keep a record of when you installed weatherstripping on each window. This helps you plan replacements before they fail completely.
Frequently Asked Questions
Can I put weatherstripping over old weatherstripping?
No. Old weatherstripping will prevent new adhesive from sticking, and layering strips makes the window harder to close. Remove the old strip completely, clean the frame, and install new weatherstripping.
What if my window frame is uneven or warped?
Uneven frames are common in older houses. Use a thicker weatherstripping or one with more give, like silicone. You may need to install strips of different thicknesses on different sides of the same window to fill all the gaps evenly.
Will weatherstripping make my window hard to open and close?
It should not if you choose the right thickness and install it correctly. If your window becomes stiff, the weatherstripping is too thick or positioned too far into the gap. Remove it and try a thinner type, or reposition it slightly outward.
Do I need to weatherstrip the top and bottom of the sash too?
Yes, if you want to seal all air leaks. The meeting rail (where the top and bottom sashes meet on a double-hung window) is a major source of drafts. Install weatherstripping on both the top sash and bottom sash at this point, or use V-strip in the channels on both sides.
How much money will I save on heating and cooling?
Savings depend on how many windows you weatherstrip, how old your windows are, and your local climate. Weatherstripping typically reduces air leakage by 10 to 20 percent around the window. In a house with many drafty windows, this can lower heating and cooling costs by a few percent per year, but the exact amount varies widely.