I remember my GCSE physics teacher telling us a story about the last time he bought a house. It was the middle of winter and had been snowing heavily.
He was worried about how much it would cost to heat so walked to the bottom of the garden and looked at the roof.
Unlike the houses either side, it had no snow on its roof. He concluded that the insulation was inadequate and answered his own question.
He was clearly just being naive. For there is another perfectly reasonable explanation for why the snow may have melted...