It can seem a contradiction but the snow can help you keep your house warm. This can happen in two ways.
Firstly, a covering of snow can help reduce the wind chill factor from extracting the heat from surfaces that are covered with snow. For instance if your roof is covered with 4 inches of snow and say that the temperature is -3 degrees and there is a 20 mile an hour wind. The wind chill factor will make the temperature have a cooling affect of about -13 degrees. Your roof though thinks that it is only -3 and therefore the level of heat loss is reduced because the differential is reduced.
Secondly, when the temperature rises above freezing, go and have a look at your roof covered with snow. See where the snow melts first. Compare this with any neighbours nearby and see which parts of the roofs lose their snow covering first. (You have to consider exposure, aspect and other factors too.) These weak points may be due to thermal weak points and show which parts of which roofs need insulating most urgently.
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