That is good for temperate climates in the right season when there is a big difference between day and night. It's a terrible design for consistently hot or cold places. i.e. Norway in the winter you're running some kind of heating (coupled with insulation) around the clock. A large thermal mass would just be constantly sapping that energy away. In Spanish summers a large thermal mass just means you don't get to take advantage of the slight cooling you get at night.