During the cold months, windows are a welcome house feature. They bring natural light, warmth, and a glimpse of the outside world. But windows aren't so welcome when they allow cold drafts of air into the home. Windows account for about 30-percent of energy loss, and a large part of that loss is due to drafts. Over 75-percent of the sun that enters homes through windows becomes heat. Yet drafty windows significantly cut into that thermal heat gain.
Replacing windows is the ultimate solution to drafty windows, but it's a costly fix. Instead, learn how to fix drafty windows with simple items like caulk, plastic film, and even nail polish. For more extensive fixes, use thermal blinds, interior storm windows, or replacement window sashes.
Equipment / Tools
- Caulking gun
- Hair dryer
- Hand saw
- Draft stopper
- Self-stick vinyl foam weatherseal, 3/8-inch wide, 3/16-inch thick
- Paintable caulk
- Sash lock
- Clear nail polish
- Thermal insulating film
- Thermal blinds
- Window sash
- Rigid foam insulation
- Reflective bubble-style insulation
Use a Draft Stopper
One crucial area where drafts pass through windows is under the sash. Setting a thick, weighted cloth draft stopper on the window sill puts an end to drafts trying to crawl under the window. You can either purchase a draft stopper or make your own in just a few minutes.
Buy a draft stopper: When purchasing a draft stopper, look for one that is the width of the window. Door and window draft stoppers are often the same product. Make sure that it's a single tube and not a double-sized stopper called a sweep or a twin door draft stopper. Cost ranges from $15 to $20.
Make a draft stopper: Fill a cut-off pant leg, leggings, hosiery, or knee socks with dry rice, lentils, or popcorn kernels. Sew up the ends or tie with colorful yard or string.
What Is a Window Sash?
A window sash is the assembly of glass, framework, and peripherals that moves up and down (or side to side) when you open or close the window.
The inside of the window jamb—the area between the window frame and the window sash—might have large gaps that let drafts through. If it's gapped enough for drafts, it might be large enough to apply self-stick vinyl foam weatherstripping.
- On double-hung windows, raise the lower sash.
- Measure the distance from the bottom of the window opening to the bottom of the raised sash. Add 2 inches to the measurement. Cut the weatherstripping.
- Peel off all but the last few inches of backer from the weatherstripping. Tear the backer, leaving the rest of the backer in place.
- Add the weatherstripping to the side of the window. Push the final few inches of weatherstripping through the side of the window and remove its backer.
- Repeat on the other side of the window.
- Add weatherstripping along the bottom of the sash.
Seal Window Molding or Trim
Some drafts that appear to be coming through the window actually originate from around the window—specifically, the wood molding or trim. Removing the trim, sealing any cracks, and then replacing the trim is one way to stop major drafts. An easier way, best for minor drafts, is to seal around the trim without removing it.
- Use a utility knife to carefully remove any loose caulking around the window trim.
- Cut the tip of the caulk tube at an angle with scissors. Use caulk specified as paintable or painter's caulk. Silicone caulk cannot be painted.
- Starting at the top of the window trim, run a thin bead of caulk between the trim and the wall. Work downwards.
- Immediately follow by running a latex-gloved finger along the bead to smooth it out and bevel it.
Replace Sash Locks
A window sometimes is drafty because the window sash isn't firmly locked in place. The sash lock not only keeps you secure from intruders but also pushes the bottom sash down and the upper sash up.
When the sash lock is faulty or loose in the window frame, the window won't lock tightly into place, so air escapes from both the bottom and the top of the sash. Replacing the sash lock is easy and costs from $5 to $15 per lock.
- Purchase a new sash lock that exactly matches the style of the old lock.
- Unscrew and remove both halves of the existing sash lock.
- Tightly close the window.
- Position the latch side and receiving side of the lock over the old holes.
- Screw into place with the provided screws.
Fix Cracked Glass
Cracked window glass will allow drafts to seep through. Cracks can be sealed semi-invisibly with clear nail polish.
- Using a cloth (not a paper towel), clean the crack and surrounding area with isopropyl alcohol. Let it dry.
- To avoid damage from drips, cover the area around the crack with painter's tape. Cover the floor and sill with cardboard or paper.
- Load up the nail polish brush with polish.
- Dab the crack with the brush to push polish into the crack.
- Spread a smooth coat of polish around the crack to help strengthen the area.
Apply Thermal Window Insulating Film
Thin, crystal-clear plastic called thermal insulating film blocks window drafts from entering the room. The film can be removed at the end of the cold season.
- Clean the window molding or trim with warm water and a mild detergent.
- Rinse with a damp cloth to remove soap film. Let dry.
- Measure the width and height of the window, then another 1-inch on all sides.
- Cut the window film to size.
- Apply the double-sided adhesive tape to the window molding on all sides. Remove the liner on the tape.
- Unfold the window film and apply it to the double-sided tape.
- Pull the film off and re-stick as needed to tighten the film.
- Turn a hair dryer on low and point it about 6 inches away from the film. Move the dryer around the film to remove the wrinkles and tighten up the film.
Install Thermal Blinds
Honeycomb cellular shades are a type of thermal blind that trap air in its double-walled design. Cellular shades have the highest R-value of any type of interior window covering.
Though the main function of cellular blinds is not to trap drafts, cellular blinds can be used in conjunction with other methods to significantly save energy and increase comfort in the home.
Since cellular blinds are solid and mini-blinds with individual slats are not, they will block drafts better than mini-blinds.
Replace Window Sash
More than a minor fix, less than a major window replacement, removing and replacing a poorly performing window sash can work wonders for drafty windows.
Sash replacement kits are brand-specific, so search for your window's manufacturer and model name or number, if possible.
Install Interior Storm Windows/Inserts
Interior or invisible storm windows are retrofit inserts that go on the inside of the house to trap air in the window well, improving interior heat retention. They also block drafts.
Interior storm windows either fit on the inside of the window jamb by compression or they attach to the window molding with magnetic strips.
Unlike thermal window insulating film, interior storm window inserts can be taken down at the end of the cold season, stored compactly away, and then reused next year.
Close Window Temporarily
When a drafty window is too severe to be fixed by other means, consider temporarily closing up the window with rigid foam insulation and a roll of reflective bubble-style insulation.
- Measure the inside dimensions of the window frame. Also measure the depth of the window well.
- Transfer the measurements to a sheet of 2-inch-thick R-7 or R-8 rigid foam insulation. Different thicknesses of rigid foam are available, from 1- to 4-inch.
- With a hand saw, cut the rigid foam to size. Do not undercut the size. Cut the exact size.
- Compression-fit the foam into the window well.
- Cover with reflective bubble-style insulation. Tape the insulation to the window molding.
Blocking the means of egress may not be allowed, especially if other means of egress are unavailable or limited.
When to Call a Professional
If you've tried all of the methods for how to fix drafty windows and your home still experiences drafts, it's likely time to replace the windows.
Replacement windows fit into the existing window frame. On average, a vinyl replacement window costs $800 to $1,300 per window, installed.
Energy Efficient Window Coverings. EnergyStar
Sealing Behind Window & Door Trim Project. EnergyStar
Applying Plastic Over Windows Project. EnergyStar
Testing the Performance and Dynamic Control of Energy-Efficient Cellular Shades in the PNNL Lab Homes. Pacific Northwest National Laboratories
Keeping the Heat In. Government of Canada
Chapter 10 - Means of Egress. International Building Code (IBC)