Attic frost and ice damming

We’ve just come through a whopper of a record breaking cold spell that will undoubtably cause a heap of pain for many in our area. Have a look at this from an inspection yesterday.

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Ouch, that’s going to ruin someone’s happiness this year! Probably another recommendation to use an ice&water type membrane underlayment.

In our neck of the woods, seldom do I see ice penetrating the deck as the issue. The culprit is condensation resulting from heat loss originating from “somewhere” below. Insufficient attic insulation, blocked soffit intakes, frost sealed/snow covered attic vents/exhaust dampers, poorly connected bathroom/dryer/furnace exhausts and my favorite … uninsulated ceiling pot lights the homeowner installed themselves. -30 Celsius outside and 22 Celsius inside with a moist cloud forming in the attic creating a hoar frost chandelier on any cold surface it bumps into. Quite spectacular when you shine a light into it. We then get these things called “Chinooks” that can move your outdoor temperature from -30 to plus 10 in a 24 hour period. When that happens, the attic melts.

Need I say more?

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Thank you for that great info. Your review of attic problems makes me think that some young, or old, enterprising person could make a living just offering to inspect and repair all those problems. I’m just happy that I don’t live in your part of the world. . .

Primary sources are dryer, kitchen, and bathroom vents leaking. Secondary are plumbing vents and furnaces. If all those are right and tight, consider the ridge / eave vent system. Ridge vents do not have the free vent area advertised when the atmospheric conditions are factored in. Snow and ice on the roof make the deck the condensation point. Daily freeze/thaw cycles and the slow air exchange intake at the eave provides a humid air flow across the cold underside of the deck, creating the frost build up. If you’ve ever cut into a completed roof with the “balanced ridge vent system” in hot weather you’d better wear safety glasses due to the pressurized sawdust blowing up out of the cut.
I learned a long time ago not to believe anything a salesman or a pocket protector wearing engineer says.
Rant for the day …