What is the best siding for Ontario winters?

The thing to design against in Southwestern Ontario is not cold. It is the number of times the wall crosses the freezing point.

London and the surrounding region cycle through zero repeatedly from December to March. Water gets into a joint, freezes, expands, opens the joint slightly, thaws, and gets in a little further next time. Absolute cold does almost nothing to a wall by comparison. Freeze-thaw cycling does the damage, and it is why detailing matters more here than product does.

Vinyl is the regional default for good reasons: cost, availability, and colour that runs through the panel rather than sitting on top of it. Its weakness is cold impact. Vinyl goes brittle below freezing, and a panel that would flex in July will crack in January — a stone thrown up by a snowblower is the classic January call. First-generation vinyl from the 1980s and early 1990s is noticeably worse for this than current product.

Insulated vinyl adds contoured foam behind the panel. The two real benefits in this climate are continuous insulation that interrupts thermal bridging through the studs, and backing that stops an uneven older wall reading as wavy. It also takes impact better than hollow vinyl because there is something behind the panel. It is not a substitute for attic and air-sealing work, which returns more per dollar.

Fibre cement is dimensionally stable through the freeze-thaw range, holds colour far longer, and takes impact without cracking. Its requirements are specific and non-negotiable: sealed cut ends, correct ground and roof clearance, and correct fastening. Get any of those wrong and moisture gets into the core, where freeze-thaw will find it.

Engineered wood handles cold and impact well, cuts with ordinary woodworking tools, and gives a wood profile without cedar maintenance. Every field cut has to be primed and sealed, and base clearance has to be right, because it is a wood-based product.

Aluminum is what a great many 1950s to 1970s houses in this region still wear. It does not crack in cold — it dents, permanently, and its finish chalks out after a few decades. That is why hail claims on aluminum walls get scoped as replacement rather than repair.

There is also a separate question about installing in winter rather than living through it. Vinyl handled below roughly −5 °C cracks on cutting and flexing, so the practical installation season in this region runs from late spring into the fall. A contractor offering to hang vinyl in February is telling you something about how they work.

If cost is the constraint, standard vinyl installed properly beats fibre cement installed badly every time. Detailing is what survives an Ontario winter, not the product name on the box.

Written by the team at siding contractor in London, Ontario.