How to Weatherstrip Old Windows

Drafts are the silent tax-payers of any aging home. When a window stops sitting flush against its frame, the air exchange between your comfortable interior and the biting exterior isn't just a nuisance; it's a direct hit to your heating and cooling efficiency. Weatherstripping restores that barrier without the expense or structural headache of full window replacement. Done well, this project is invisible. The goal isn't to glue your window shut, but to create a compression seal that prevents air movement while allowing the sash to move freely. You are looking for a clean, uniform look that hugs the contour of the frame, ensuring that the next time the wind picks up, the only thing you hear is the glass rattling slightly rather than the air whistling through it.

Clean Every Surface First. Open the window fully and scrub the frame tracks with a stiff brush or rag dipped in rubbing alcohol. Remove all dirt, loose paint, and old, crumbling adhesive to ensure the new strip sticks permanently.
Spot Every Leak. Close the window and use a flashlight to identify where the light leaks in between the sash and the frame. Measure the width of the gap to choose the right thickness of weatherstripping.
Cut with Precision. Cut your V-seal or foam tape to the exact height and width of your window frame sections. Leave a tiny bit of overlap at the corners to ensure a continuous seal.
Press Firmly, Top Down. Peel back the protective backing of the strip a few inches at a time, pressing it firmly into the frame. Start at the top and work your way down so the weight of the strip doesn't pull it off while you work.
Reinforce the Bottom Edge. Apply a heavier-duty rubber or bulb-style seal to the bottom sash edge where it meets the sill. This is the area with the most movement and highest air infiltration.
Test Smooth Operation. Slowly open and close the window to check for resistance. If the window is too hard to move, trim the excess bulk from the strips until it operates smoothly but firmly.