How to Winterize Your Windows

Winterizing buys time — it doesn't fix a failing window

Every one of these steps addresses air leakage around a window, not the window's actual insulating performance. If your windows are single-pane, decades old, or have a failed seal (see condensation between window panes), winterizing will reduce drafts but won't come close to what a modern energy-efficient window delivers. Think of it as a genuinely useful, low-cost way to get through one more winter — or a permanent supplement even after you've replaced windows, since even good windows benefit from a well-sealed frame.

Step by step

• Find the drafts first. On a cold, windy day, run your hand around the window frame and sash, or hold a lit candle/incense stick near the edges — visible flickering or a felt draft tells you exactly where to focus.
• Caulk exterior and interior gaps. Use exterior-grade caulk on any gaps between the window frame and siding/trim outside, and interior caulk or sealant where trim meets the wall inside. Don't caulk the operable parts of the window itself, or you'll seal it shut.
• Replace worn weatherstripping. The foam, felt, or vinyl strip that seals the sash against the frame compresses and cracks over years. Fresh weatherstripping is inexpensive and is often the single biggest draft-fix on an older window.
• Add a window insulation film kit on your worst-performing windows — shrink film applied with double-sided tape and tightened with a hair dryer creates an extra air pocket that noticeably cuts drafts for the season. It's removable in spring.
• Install storm windows if you have the original frames for them — see storm windows: cost and are they worth it for a bigger step up without full replacement.
• Use heavy curtains or cellular shades, closed at night, especially on north-facing windows — this is a low-cost, ongoing insulation boost that works with everything else on this list.

Pro tip from our network contractors

Do the draft-test walk-around on the coldest, windiest day you can, not a calm afternoon — small leaks that are invisible in still air become obvious the moment wind is pushing against the house.

When winterizing isn't enough

If you're doing this every single year on the same windows and still feeling drafts, wrestling with condensation, or watching heating bills climb, that's the sign the windows themselves — not just the seals around them — have reached the end of their useful life. See signs you need new windows and energy-efficient windows for what a permanent upgrade actually buys you.