A drafty door or window is costing you money every day it goes untreated. The U.S. Department of Energy estimates that air leaks around windows and doors account for 25 to 30 percent of a home’s heating and cooling costs. Weatherstripping fixes that. A full door costs $10 to $20 in materials and takes about an hour to do properly. The energy savings pay for it in the first month of a cold winter.
Most people replace weatherstripping either too rarely or incorrectly. Here is how to do it right.
How to tell if you need new weatherstripping
The easiest test is the paper test. Close a door on a piece of paper so the paper is between the door and the frame. If you can pull the paper out easily without tearing it, the seal is not tight enough and weatherstripping needs attention. Do this at several points around the door: top, both sides, and bottom.
You can also hold a lit incense stick or a thin strip of tissue paper near the edges of a closed door or window on a windy day. Movement in the smoke or paper indicates air coming through. On the outside of a door, run your hand slowly along the edges and you may feel air movement directly.
Types of weatherstripping and where they go
Foam tape with adhesive backing is the easiest to install and works well on window sashes and on door frames where the stop meets the door. It compresses when the door or window closes and creates a seal. It is the least durable option and typically needs replacing every one to two years, but it is cheap and goes on in minutes.
V-strip (also called tension seal) is a folded strip of metal or plastic that you press into the channel of a door or window frame. It springs back against the moving part when the door or window closes. It is more durable than foam and works particularly well on the sides of doors and double-hung windows. V-strip typically lasts five to ten years.
Door sweeps attach to the bottom of the door and seal against the threshold. The bottom of a door is where most air infiltration happens and where energy is lost most readily. A door sweep costs $5 to $15 and makes a significant difference in a drafty room. Choose one that adjusts so it does not drag on the floor when the door opens and closes.
Bulb or D-profile weatherstripping made from rubber or foam with a nailing flange is the most durable option for door frames. It is stapled or nailed into the door stop and provides a reliable seal for many years.
Removing old weatherstripping
Pull off the old weatherstripping before installing new. Adhesive-backed foam peels off and usually leaves adhesive residue behind. Clean the residue with Goo Gone or a rag dampened with rubbing alcohol before applying anything new. New adhesive will not bond well over old adhesive residue.
Stapled or nailed weatherstripping can be pried off with a flathead screwdriver or a pry bar. Remove any remaining staples with pliers before installing new material.
Installing foam tape weatherstripping
Clean the surface where the tape will adhere with rubbing alcohol and let it dry completely. Adhesive sticks dramatically better to a clean surface than a dirty one. Cut strips to length with scissors, peel the backing, and press the foam firmly into place along the door stop or window sash channel. Close the door or window to check the compression. The foam should compress slightly when closed, creating a seal without making the door or window hard to open.
Installing a door sweep
Close the door and mark the height where the existing threshold or floor sits relative to the door bottom. Open the door and hold the sweep against the door bottom so the flexible flap sits at or just below that mark. Mark the screw hole positions, pre-drill to avoid splitting the door, and screw the sweep in place. Open and close the door several times to confirm the sweep creates a seal without dragging excessively on the floor surface.
Weatherstripping windows
Double-hung windows seal best with V-strip pressed into the channels where the sashes slide. Cut strips to the full height of the channel, press the V-strip in with the open side of the V facing the sash, and tap it in with a hammer if needed. The sash pressing against the V when closed creates the seal.
For the horizontal seam where the upper and lower sashes meet in the middle of the window, foam tape applied to the top of the lower sash rail or the bottom of the upper sash rail creates a good seal when the window is closed.
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