The best way that I can think of to add a large amount (20+ tonnes) of thermal mass to a solar home is by adding concrete floors. By doing this, one can get two uses, thermal storage and a finished floor,  out of the same investment. Furthermore, since the mass of a concrete floor is so spread out around the home, thereby giving it a large surface area with which to absorb and release heat, it really is the ideal thermal storage medium for a house with large solar gains.

So we added a 2.5 inch topcoat of concrete over the subfloor. In order to support the extra weight we had to add (recycled!) beams that run the length of the house (north to south).  After it was poured, the concrete was simply trowelled as a preliminary finish.

pouring concrete floors over a regular subfloors (the walls had to be made 2.5 inches higher to compensate for the depth of the floors)

a freshly trowelled concrete floor

For the final finish, we were partial to an acid-stain because we’ve seen some gorgeous stained finishes. Peter Amerongen convinced us to go for a water-based dye for environmental reasons. Man those green types can get in the way sometimes!

A talented man named Skip from Desco Coatings did the final finish. Peter describes the finish as such:
”We sealed the concrete with lithium silicate, then dyed it with water-based dye. The final coat was an epoxy coating, 2-part , 100% solids (so no offgassing because the solids do not evaporate).”

The finished product is wonderful – a bit different at first, with an organic, charactery type of feel to it (yes, I just made up the word charactery).

The floor has been growing on me by the day.

we love the saw cuts in this floor

the variations in the floor’s texture took a bit of getting used to.

mmmm…floor near recycled-fir stairs

(cross-posted at greenedmonton.ca)