A drafty window can leak air through moving sashes, frame joints, or gaps around the window unit. Locating the exact leak lets you choose weatherstripping, caulk, or repair without blocking drainage paths or moving parts.
Find the leak on a windy day
Move your hand slowly around the sash, frame, and trim or use a lightweight strip of tissue to detect airflow. Do not use an open flame near curtains or finishes to hunt for drafts.
Use weatherstripping on moving joints
Sashes and operable joints need compressible weatherstripping that seals when closed but still allows movement. Choose a thickness that closes the gap without straining hardware or preventing the window from latching.
Caulk fixed gaps with a compatible sealant
Fixed joints between the frame and trim can be caulked when clean and dry. Do not block weep holes, vents, or channels designed to drain water from the window assembly.
A draft may come from behind the trim
If air comes through trim even though visible joints are sealed, insulation may be missing around the window. Removing trim or adding foam requires control of expansion and moisture; installation defects may need broader repair.
Sources
- U.S. Department of Energy — Thermostats — Thermostat use, temperature setbacks, and heating and cooling energy savings.