Winter cold, summer smoke: rethinking cold climate home renovation in the north

A house built to survive minus 35 should be able to keep July wildfire smoke outside. Most of them can’t. Homeowners across Northwestern Ontario have learned that the hard way over the past few smoke seasons, and the explanation turns out to be more useful than it first sounds.
The short version: keeping heat in and keeping smoke out are not the same job. Northern housing was optimized for the first one.
Why does smoke get into a house that handles minus 40 just fine?
Because insulation an