Freeze-thaw at the flashing in Utica
一年 100 天日夜跨越冰點但積雪只有 0 cm——損傷集中在煙囪與天溝的收邊，不是冰壩; 屋齡中位 1940 年——多數屋頂已經換過至少一次，接縫與收邊的做法是上一代的.
一年 100 天日夜跨越冰點但積雪只有 0 cm——損傷集中在煙囪與天溝的收邊，不是冰壩
屋齡中位 1940 年——多數屋頂已經換過至少一次，接縫與收邊的做法是上一代的
Utica crosses freezing between night and day on about 100 days a year, and each of those cycles melts a little roof snow and refreezes it lower down.
How the damage actually happens
Heat leaking into the attic warms the middle of the roof deck while the eave, which overhangs unheated air, stays below freezing. Snow melts up high, runs down, and refreezes where the deck is cold. The ridge of ice that builds up holds the next lot of meltwater against the shingles, and shingles are designed to shed water downhill, not to hold it.
The median home in Utica dates from 1940, so most roofs here are on their second or third covering and the detailing underneath is of that era.
What actually fixes it
- Air-seal the attic floor so heat stops reaching the deck - this is the real fix
- Insulate to the depth the code calls for, after sealing, not instead of it
- Ventilate soffit to ridge so the deck stays close to outside temperature
- Only then consider membrane at the eave, which limits damage rather than preventing ice
Heated cables are the opposite of a fix: they melt a channel through the ice, use electricity every winter, and leave the cause untouched. They have a place on a roof that genuinely cannot be ventilated, and nowhere else.
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