How to Weather-Strip Windows for a Warmer House This Winter

Follow our step-by-step guide to weather seal windows for a warmer winter and a cooler summer.

Most heat loss at a window occurs through gaps between the sashes and the frame; even small gaps can be big energy wasters. To find out if your windows have gaps, hold a piece of tissue paper or plastic wrap near the window on a windy day and move it around. Wherever you see movement (either outward or inward), there's a significant leak. If you have drafty windows, follow our step-by-step instructions to learn how to weather-seal windows to conserve energy and save money.

Before you begin, make any needed repairs to the window and its frame. Once complete, the first step to weather-seal windows is to caulk, especially on the exterior. Also, check that the glazing putty on the outside is free of gaps and seals tightly against the window. Where glazing is failing, scrape it out and apply new glazing. On the inside, see that the joint between the glass and the sash is sealed with paint.

Weather-stripping where two surfaces push together (the horizontals of a double-hung window and the verticals of a casement or sliding window) is straightforward. Where two surfaces slide against each other (the verticals of a double-hung window and the horizontals of a casement or slider) calls for more precision. However, most weather-stripping applications only take an hour or two to apply. We'll show you how to do both with our guide to weather-stripping windows.

illustration of gaps in windows
Dave Toht

Before You Begin: Identify Gaps in Windows

A double-hung window has several potential leak points. Most prominent are where the bottom of the upper sash meets the top of the lower sash, the sashes slide against the jamb, and the bottom sash meets the stool. These gaps must be sealed with weather-stripping. Gaps can also be found outside the casing, the underside of the stool, and the apron.

Types of Weather Stripping

Nail-on weather-stripping is the most durable choice if you have a wood window. Spring bronze works well for gaps that are consistent in width. It's also the best-looking product. A tubular vinyl gasket is a good choice weather-seal for windows when the gap is large and uneven, and looks are not as important. Strips of felt are a poor choice because they don't seal well and aren't durable.

Self-adhesive weatherstripping is easy to cut, making it the most convenient choice. If you choose self-stick V-strip tape, be sure it is made of EPDM (ethylene-propylene-diene-monomer), which stays flexible for many years, even when exposed to extremely low temperatures.

Foam weather-stripping is easy to apply and fills large and uneven gaps effectively. However, it usually doesn't last long. Open-cell foam is the best at bouncing back after being compressed, but it can only be used on the inside. Closed-cell foam is weather-resistant but short-lived.

For a quick but temporary window weather seal, use rope caulk or a shrink-wrap plastic window kit, which can be removed when the weather gets warm.

dining area in front of windows
Reed Davis

How to Weather-Strip Windows

Repair drafty windows with these simple tips.

What You Need

  • Tape measure
  • Tin snips
  • Scissors
  • Caulk gun
  • Hammer
  • Drill
  • Weather-stripping
  • Brads
  • Caulk
  • Spray foam insulation
  • Fiberglass insulation
  • Rags
  • Mineral spirits (if needed)
cutting caulk tube
Dave Toht

How to Caulk Around a Window

Step 1: Cut Caulk Tube

Cut a caulk tube's tip using a sharp utility knife; a straight, clean cut contributes to a smooth caulk line. Some people prefer to cut at a steep angle, while others prefer a nearly straight cut. Cut near the tip for a small bead of caulk. Some caulk tubes require the seal to be broken with a wire or long nail through the tip.

applying caulk to window
Dave Toht

Step 2: Apply Caulk to Window

It takes a bit of experience to produce a smooth bead of caulk, so start caulking in an inconspicuous location. Get in a comfortable position and rest the tip against the joint. Squeeze the trigger until caulk emerges, then continue to squeeze as you move the tip along the joint.

smoothing caulk with finger on window
Dave Toht

Step 3: Smooth Caulk

If the bead looks good, leave it alone. Otherwise, use your finger to smooth it. While this tends to smear the caulk, it ensures the caulk adheres to your surface on both sides of the bead.

prepping to seal window
Dave Toht

How to Seal the Top or Bottom of a Window

Add Rope Caulk

For an added measure of weather-stripping during cold months, apply rope caulk ($7, The Home Depot), which helps seal various window materials. To install rope caulk, unroll and press in rope caulk where the sash meets the stops, between the top of the lower sash and the bottom of the upper sash, and in the pulley. The window can't be opened while rope caulk is in place, so remove it in the spring.

applying self-stick foam weatherstripping
Dave Toht

Apply Self-Stick Foam Weatherstripping

Another option for sealing windows, adhesive foam weatherstripping (from $3, Lowe's) is inexpensive and easy to install; simply peel and stick. Test to be sure you can close the window before applying thick foam weather-stripping to the underside or top of a sash. To apply self-stick foam weather-stripping, first make sure the surface is clean and dry. Cut the foam with scissors or tin snips. Peel off the backing and press the foam into place.

Self-adhesive foam works well for casement windows and sliding windows. It can also be used to insulate the sides of windows. The foam comes in various thicknesses; test to be sure the window will close after you apply it.

installing spring bronze weatherstripping
Dave Toht

Install Spring Bronze Weatherstripping

While modern weather-stripping techniques like foam and adhesive are popular today, spring bronze weather-stripping offers a long-term solution. This technique involves more work (nails are required) but provides a solid window seal to prevent air from escaping your home.

To install, first cut spring bronze with tin snips to fit your window precisely. Take care not to bend the metal as you work, hold the piece, and drive in small nails. Next, drive two or three nails, test to be sure the window will close, then drive the rest of the nails until they're flush with the surface. If needed, use a putty knife to gently bend the bronze once it's in place to close gaps in your window.

To install spring bronze along the sides of a lower sash, raise the sash all the way up. Cut the bronze to the height of the sash. Slip it up the sash as far as needed, nail in place, then close the sash to test.

sealing a window with tubular vinyl
Dave Toht

Seal Windows with Tubular Vinyl

Tubular vinyl ($4, The Home Depot) is an affordable solution for sealing large cracks. However, it can detract from the appearance of a window. To install tubular vinyl weather-stripping, cut the strips to size with scissors. Then, close the window and firmly press the vinyl while driving small nails or staples.

installing plastic shrink wrap on window
Dave Toht

Install Plastic Shrink Wrap

To seal a window for the winter season only, purchase a shrink-wrap window cover kit ($15 for 10 pack, Walmart). This plastic for windows blocks drafts during cold months to help keep your home energy-efficient. First, use scissors to cut the window plastic to size. Apply the included double-sided tape all around the window casing, then carefully apply the plastic to the tape. Use a blow dryer to shrink the plastic and make it taut.

How to Seal the Sides of Windows

Many techniques to seal the top and bottom of windows can also be used to stop drafts on the sides of windows, including self-adhesive foam and spring bronze. Here are additional weatherizing techniques for the sides of windows.

repairing glazing putty on window
Dave Toht

Repair Glazing Putty

If you notice that the glazing putty on your window is cracked, missing in spots, or curling from the glass, you'll need to repair it. Use a putty knife or chisel to scrape away loose putty. Clean the area, apply a little linseed oil, and apply window glazing putty ($11, The Home Depot).

attaching v-seal weatherstrips to window
Dave Toht

Attach V-Seal Weatherstrips

For a casement window or sliding window, V-seal weatherstripping ($4, The Home Depot) can be added to the side of the window sash or jamb for a good seal. First, make sure the surface is clean and dry. Cut the V-strip to fit your window and hold it in position. Peel back the paper as you press the self-adhesive strip in place.

caulking exterior molding
Dave Toht

Caulk Exterior Molding

If you can't identify where the draft is coming from on your window, check your home's exterior. The window's exterior molding may need to be repaired. To seal windows, caulk around all exterior window molding and the inside of the molding and under the sill.

insulating counterweight openings
Dave Toht

How to Insulate Counterweight Openings

If you've installed a replacement window or sashes, the cavity for the sash weights can be filled with insulation. Fill the opening by gently stuffing it with fiberglass insulation or with spray foam (the nonexpanding type is easiest to control).

sealing a window pulley
Dave Toht

How to Seal a Window Pulley

Cold winter air can enter your home through the pulley slots. Plastic covers are available, or you can press in removable rope caulk to fill the gaps. Or simply cover with duct tape. Remove the caulk or tape before opening the window in the spring.

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