I built a house for a friend of mine, and the walls are two feet thick. The house is 30x60 with two floors. He uses a 1 or 2 gallon electric boiler to heat the floor and that is it. Even when it is -30 outside, it is like a warm spring day inside.
You can't hear all the noise from the outside world either. He lives about 150 feet from the tracks and you have a hard time telling when a train goes by.
I don't even remember what the R-value is....it was around 80 I think.
