Heat loss and the melt line
Drive any Connecticut street after a January snowfall and the roofs tell you something the houses do not. Some are still evenly white. Others have bare patches, or a clean line partway up the slope. That difference is not exposure — it is heat leaving the building through the ceiling.
Reading the melt pattern
A well-insulated, well-ventilated roof stays close to outside temperature, so the snow on it melts from the top down, slowly, when the air warms. A roof losing heat melts from underneath, in freezing weather, and the meltwater runs down the slope until it reaches the part of the roof that overhangs unheated space — the eave — where it refreezes. That is the entire mechanism, and it explains most of what people call an ice problem.
The pattern is diagnostic. Bare strips over the rafter bays with snow still on the rafter lines means insulation missing between the joists. A bare patch around the chimney means air leaking up beside it. A clean horizontal melt line partway up means the insulation stops there — very common on a cape where the finished room ends and the low attic begins. And a roof that is bare while the neighbour’s is white means the neighbour is paying less to heat their house.
Why the fix is usually not on the roof
The order that works is air sealing first, insulation second, ventilation third, and roofing last. Sealing the gaps where warm air escapes into the roof cavity — around light fixtures, the attic hatch, plumbing stacks, the top plates of interior walls — is cheap and does more than anything else. Insulation depth comes next. Ventilation then carries away whatever heat still gets through.
None of that is roofing work, and an honest roofer will say so. What replacement day genuinely offers is the one cheap opportunity to correct the ventilation side while the deck is open, and to run ice-and-water membrane far enough up the slope that the refreeze at the eave has nowhere to get in. It buys time and protection. It does not stop the heat loss that caused the melt.