The conventional wisdom is that icicles are a symptom of wasted heat. The expensive heat supposedly leaks through a poorly insulated roof and melts the snow. But just as soon as the water flows off the roof it refreezes into icicles.
But I question this. While no roof is likely to be perfectly insulated, the angle of the roof is also a factor. The sun is low in the sky in the winter and the closer to vertical the roof is the more directly the snow on it is exposed to the sun's rays.
The roof on this shed is angled. When the temperature is around the freezing point, notice how the snow on the lower section of the roof melts first. This is because the lower section is more vertical, and thus the snow on it is more directly exposed to the sun's rays.
The same principle applies to any angled roof. It exposes the snow on it more directly to the sun's rays, which causes it to melt, but, when the temperature is not far below freezing, it refreezes as it drips off the roof.
What is an indicator of losing heat is when there is a light dusting of snow on the roof and you can see the outlines of the rafters in the snow.
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