Drafty windows: what causes them, what helps, and when replacement is the only fix
You can feel it on the back of your neck when you sit by the window. Here is where the cold actually comes from, what's worth trying before next winter, and the point at which patching stops making sense.
Why windows get drafty
Most homes between Duncan and Qualicum Beach were built in the 1970s through the 90s, with windows that were never going to last this long. Wet winters, salt air near the coast and a few decades of sun have done what they do. The cold you feel almost always comes from one of four places.
The weatherstripping has failed
Sliders and older vinyl windows rely on a strip of pile or rubber to seal the sash against the frame. Over the years it flattens, cracks or comes loose, and air passes straight through the gap. This is the cheapest cause to fix, and the one most people try first.
The frame has shrunk, warped or been stressed
Wood frames swell and shrink with the seasons, and in a wet climate they eventually rot at the sill. Vinyl from the early generations can warp in the sun. Aluminum frames move with heat and cold and rarely close as tightly as they once did. When the frame is no longer square, no strip of weatherstripping can close the gap.
There's no insulation at the jamb
The window may be tight, but the gap between the frame and the wall framing was left empty, or stuffed with a little paper, when the house was built. The air comes in around the window rather than through it. You'll feel it along the trim and often see it as a dark smudge on the drywall beside the window, where dust has been drawn through.
Single pane glass, or a failed double pane
Single pane glass is thin and passes cold straight through. Even a window with no air leaks at all will feel cold to sit next to, and it will drop the temperature of the whole room. A double-pane unit with a failed seal is nearly as bad, because the insulating gap is gone. Read more on the foggy windows page.
What helps in the short term
- Replace worn weatherstripping on the sashes. It's inexpensive and worth doing on a window that is otherwise sound
- Re-caulk the exterior joint where the frame meets the siding, when the caulk has cracked or pulled away
- Hang insulating curtains or cellular shades, and close them at night
- Use a removable rope caulk or a clear window film on windows you plan to replace soon
- Seal the interior trim joint, and inject low-expansion foam into an empty gap at the jamb if you can reach it without prying the whole casing off
None of this turns a single pane aluminum window into a good window. It buys you a more comfortable winter while you plan.
When replacement is the only fix
A drafty window is usually a noisy one too: the same gaps that let the cold in let the highway noise in. Replacing it fixes both at once.
- The frame is the original aluminum, or it's rotted, twisted or no longer closes square
- The glass is single pane, or the double pane has failed and fogged
- You've re-sealed the same window more than once and the draft is back
- The cold comes from the wall around the window, and the gap there needs to be opened and insulated, which only a replacement allows
New windows from Thermoproof, built in Cobble Hill since 1977, are installed with the gap around the frame insulated, not just caulked on the outside. That is what stops the draft at the source.
Which way to go depends on what's behind your trim. A retrofit insert goes into the frame you have, and a full-frame replacement takes it all back to the wall. We tell you which one at the measure. If the draft comes with water, see our page on condensation on windows.
For a rough idea of the price, try the online estimate. We serve Nanaimo too, see the Nanaimo page for where.
FAQ
Common questions
How can I tell where the draft is coming from?
On a windy day, hold a stick of incense or a lit candle near the edge of the window, at the sash corners and along the frame where it meets the wall. A flicker or a smoke trail that bends sideways shows you the leak. Also run your hand along the trim: cold air from the wall gap and cold air through the sash feel different, and the fix is different too.
Will weatherstripping or caulking fix a drafty window?
Sometimes, for a season or two. New weatherstripping helps a sash that has lost its seal but is otherwise square, and caulk helps a cracked exterior joint. If the frame has shrunk or twisted, or the glass is single pane, you're patching a window that is giving up, and the cold you feel is also coming through the glass itself.
Are plastic film kits worth it?
For a window you plan to replace next year, yes. They are cheap and they stop air movement, and a lot of Island renters rely on them. They don't fix a failed seal or a rotted frame, they make the window harder to open and clean, and the film can trap moisture against the glass on wet days.
How do I know if I need new windows or just a repair?
If the window opens and closes smoothly, the frame is solid and the glass is clear, a repair is fair. If the sash sticks or rattles, the frame is aluminum, the glass is single pane, or there's fog between panes or soft wood under the sill, repair is money spent on something that will fail again. We look at all of this at the free measure and give you a straight answer.