Higgy, I wouldn't be too worried about what I saw on your roof. I don't see any ice, which would be a telltale sign of snow melt and lots of heat loss. Lack of snow is probably from wind, mine gets that way in places. My unheated barn has snow missing in places similar to my house, and I know the barn isn't melting it off from heat loss. So compare snow cover on your home to unheated buildings in your area . The pic below is of my in-laws house and is typical of older houses in the area. There is surely heat being lost thru that roof
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