What are the floors made of? Do I need to insulate under them?
A. The floor of a passive-solar home is the largest potential for thermal mass storage, naturally available at every site. Floors should be made of a thermally conductive material (as opposed to insulative, i.e. no W-W carpets w/foam pad) such as flagstone, slate, or Saltille (Mexican) tiles over poured concrete or adobe. I recommend a 2-3 layer of river-rock over the sub-floor with a 6-mil plastic film between rock and concrete pour or adobe. The idea being to keep sub-soil moisture from wicking up through the concrete/adobe and leaving mineral deposits (white chalky blotches) and muddy spots. In colder climates, vertical insulation should be installed around the sub-surface perimeter of the exposed foundation walls.
