Now, I’ve heard of thermal mass before, most memorably in relation to cold weather shooting with a DSLR camera, but what does Wikipedia have to say about this? I haven’t read about it in detail. Oh, wow, quite a number of interesting things. So, thermal mass is also termed thermal capacitance. Insulation inhibits thermal conductivity. Thermal mass is great for isolating a building from fluctuating external temperatures. Concrete and earth are great sources for thermal mass. Therefore, an insulated concrete slab at the base of a building can significantly improve its thermal efficiency and dynamics. Water, of course, is another great source for thermal mass, since it has a very high specific heat. That being said, the human occupants of a building are also a great contributor to a building’s thermal mass.
20181130/https://en.wikipedia.org/wiki/Thermal_mass