My boyfriend and I are purchasing a home. We recently looked at a home with what was termed a "passive solar" heating system. The home was designed as an "envelope home" in which the south side of the home was a glass enclosed two story atrium. This atrium is supposed to trap heat during the day, which heats the home, thus reducing the heating costs.
The home is otherwise heated by electricity and the bills appear to be low considering it is heated using eletricity.
I am wondering if these "envelope" homes are energy efficient and how they work.