Symptoms
- Air movement felt around the storm window edges
- Rattling in wind
- Visible gap between storm sash and frame
- Condensation building up between the storm and main window
Likely causes
- CommonWorn or missing weatherstripping on the storm sashThe foam or felt seal compresses and wears out over years.
- CommonLatch not pulling the sash tightA worn or bent latch can't apply enough pressure to seal the gap.
- PossibleStorm window slightly warpedAluminum frames can bow slightly with age or heat exposure.
- Less commonWrong size or poorly fitted storm unitAn incorrectly sized storm window will never seal well regardless of hardware.
What to do
- Inspect the weatherstripping around the storm sash for flattened, torn, or missing sections.
- Peel off old weatherstripping and press new foam or felt strip into the channel.
- Check the latch mechanism; tighten mounting screws or bend the catch slightly to increase tension if it's not pulling tight.
- Close the storm window and check for daylight gaps around the full perimeter.
- If the frame is visibly bowed, apply gentle pressure while closing to see if it seats better, and consider a support clip at the bow point.
- Clean and lightly lubricate the latch and any sliding vents on the storm window.
- If condensation forms between the storm and main window, ensure the storm window's small weep holes aren't blocked, allowing moisture to escape outward.
Tools and parts
- Screwdriver
- Weatherstripping
Storm window weatherstrippingSearch: “storm window seal weatherstrip”
When to call a pro
Call a window installer if the storm frame is significantly warped or was never sized correctly for the opening.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.