Find the drafts
On a cold day, hold a lit incense stick (or a thin tissue) along the window edges. Smoke that moves means air leaking.
Three layers of defense
Layer 1 — caulk the exterior Inspect the outside of the frame. Cracked or missing caulk? Scrape out the old, clean with a brush, apply a paintable acrylic-silicone caulk ($8/tube). Skip pure silicone — it won't take paint.
Layer 2 — weatherstrip the sash For operable windows: V-strip self-adhesive weatherstrip ($10/roll at Canadian Tire) along the channels the sash slides in.
Layer 3 — interior window film (best ROI for old windows)
- Kit comes with double-sided tape + clear shrink film ($15 for 3 windows).
- Tape around the frame, apply film, then shrink with a hair dryer. Wrinkles disappear.
- Lasts the whole winter; peel off in spring with no residue.
What to expect
- A drafty single-pane window can lose more heat than 4 m² of insulated wall.
- Film + weatherstrip on 10 windows can cut a Canadian heating bill by 5–15% per Natural Resources Canada.