How to Fix Drafty Windows

Fixing drafty windows improves comfort and reduces heating and cooling costs. According to the US Department of Energy, leaky windows and doors account for up to one third of a home’s energy loss.

How to Fix Drafty Windows

10 Drafty Window Solutions

Test for leaks with a candle, incense stick, lighter, or smoke pen by moving it slowly across and around the window. Smoke and flame are very sensitive to air movement and flicker easily when pressure changes.

Most drafty window repairs are easy and inexpensive DIY projects.

1. Lock the Windows

Window locks help keep thieves out. They are also designed to keep out cold air. Window locks force sashes tight to weatherstrip. On sliding windows, they help interlocks engage properly. Make sure all locks are engaged on casement and awning windows to create a positive seal.

Large double-hung windows are often problematic because heavy upper sashes slide down–leaving a gap at the top. Or one lock in the center can bow the sash–making locks inoperable interlocks ineffective. Add extra locks about four inches from each corner.

2. Seal the Exterior Frames

Caulk the exterior window trim to the window frame and to the exterior finish–whether siding, stucco, stone, or brick. Use good exterior caulking. Check the old caulking carefully and be prepared to scrape it off. It may look OK but could have dried and pulled away from one surface. Make sure all surfaces are clean and dry to ensure good adhesion.

3. Insulate the Window Frames

Remove the casing from around the window. Make sure to thoroughly cut any caulking to prevent damage to the wall. Remove any old insulation from the gap between the window jamb and wall framing. Spray about one inch of low-expanding window insulating foam against the back of the exterior molding. High expansion foam can bow the window fame. Fill the remainder of the cavity with fiberglass after the foam cures. Do not pack it tight. Replace the window casing.

If the gap is too small to insert the foam applicator, seal the crack with acoustic caulking. Acoustic caulking will not dry and continues to adhere to the jamb and wall framing despite any movement. Recaulk the casing to both the wall and window jamb.

4. Reglaze the Windows

Many old windows are single-pane glass in wooden frames, The glass is held in place with window putty–which eventually dries and falls off. Clean off the glass and wood frame. Remove all of the old putty. Apply new putty following the manufacturer’s directions. Replace any cracked panes of glass at the same time.

5. Install Exterior Storm Windows

Exterior storm windows come with a pre-punched fin for mounting on the exterior window trim. They are available in many standard sizes, and can also be custom ordered. Standard configurations include single hung, double hung, and horizontal sliders–allowing windows to be opened on warm days.

Storm windows are single glazed. Combined with resealing exterior frames and insulating the interior frames they eliminate drafty windows. Order them early to avoid extended delivery times. Window companies or direct from the manufacturer are the best options. Big box stores do not seem to be carrying them anymore.

6. Install Interior Window Insulation Kits

Window insulation kits are clear plastic that cover the entire inside of the window. Apply the double-sided tape onto the casing. Stick the plastic film to the tape and use a hair dryer to shrink it tight.

The kits are one and done. They are not reusable. Make sure the window is clean before installing the plastic. The window can’t be opened without removing the covering.

7. Replace Window Weatherstripping

Window weatherstripping varies greatly–from aluminum fins to mohair to compression foam. Purchase matching parts online or from home improvement stores. Online stores specializing in window parts and weatherstripping are the best option for older windows that are no longer in production. Some manufacturers like Pella have proprietary parts–including weatherstripping.

Some vinyl window weatherstripping is welded into the frame and cannot be replaced. You can usually overcome this problem by attaching self-adhesive compression foam weatherstrip to the sash or frame. Ensure a positive seal when the sash is closed and locked.

8. Use Window Snakes

Window or door snakes are long tubes two or 3 inches in diameter filled with sand or rice. Lay them on the windowsill against the sash or glass to prevent drafts. The bottom of windows always feels drafty because any cold air “falls” down the window face and is directed into the room by the sill.

Snakes are available online or from home improvement outlets. Or make your own using an old pant leg or stocking and filling it with sand or rice. You can customize the size and filling density.

9. Install Heavy Window Coverings

Thick heavy curtains stop drafts–or at least direct cool air to the floor. A spare heavy blanket or quilt accomplishes the same thing. They are quicker to install and usually cost less. On very cold nights, heavy window coverings often result in frost on the windows because of restricted airflow.

10. Replace Windows

Replacing windows is the ultimate draft repair. They have better glass with a higher R-value. New windows also address many of the issues above. Installed properly, they are sealed on the outside, insulated and finished on the inside, and lock and seal.

Window replacement costs range from about $500.00 to $1500.00 supplied and installed. Sometimes more–depending on size, style, and location.