Ridge vents in snow
A ridge vent is the standard exhaust on a modern roof and it works well, in summer. In a climate where snow sits on the ridge for weeks, it has a failure mode nobody mentions at the quote: a vent under a foot of snow moves no air at all, and it is buried during exactly the months when the attic most needs to stay cold.
- 1 Ridge caps. Thin, exposed, and worked loose by a winter of freezing and thawing.
- 2 The field. One layer or two, and the answer changes what a tear-off costs.
- 3 Valleys. Leaves mat where two slopes drain as one, and snow sits on top of them.
- 4 Flashing. Old masonry chimneys, and the saddle behind them that should shed snow.
- 5 The vent boot. A collar that goes brittle in the cold and splits without warning.
- 6 Eaves and ice dams. Where escaping attic heat melts snow that refreezes at the edge.
The winter blind spot
Ventilation matters in winter for a reason that surprises people: the point is to keep the roof deck COLD, so the snow above it does not melt and refreeze at the eave. An attic that cannot exhaust warms up, and the melt line appears. When the ridge vent is the only exhaust and it is under snow, the system stops precisely when it is supposed to be working.
A second, quieter problem: fine dry snow can be driven into a poorly baffled ridge vent and melt inside the attic, where it looks exactly like a roof leak and gets chased as one. Homeowners find damp insulation near the ridge after a cold snap, call about a leak, and the roof is intact.
What to specify here
A ridge vent with an external baffle, the raised profile that deflects wind and driven snow over the opening rather than into it, rather than the thinnest rolled product. Adequate net free area, matched to intake at the soffits, because exhaust without intake pulls conditioned air up out of the house and makes both problems worse. And on houses with long ridges or complex rooflines, ask whether the ridge alone is sufficient or whether additional exhaust lower on the slope is warranted.
The single most useful question at the quote stage is simply: what happens to this ventilation system when the ridge is under snow for three weeks? A bidder who has an answer has thought about this climate. A bidder who has not heard the question before is quoting a roof for somewhere else.