I just measured the temperature in my unfinished basement and it’s been mid to high 60s all weekend, though the temperature outside has been teens and 20s. And it’s not because of the furnace being down there, because it does not vary significantly on different sides of the basement. And the reverse is true in summer.
Question is whether this is simply the result of the ground being insulation combined with the heated (or cooled, in summer) house or whether the ground itself actually provides some heating or cooling.
The difference would be if I insulate the basement from the ground. Does that make it more or less energy efficient? My first thought is that it’s even more energy efficient, but then I started to wonder. (The question is how to structure the heating/cooling should I finish the basement.)