Tim--
I spent some time in an earthship built by an acquaintance while living near Flagstaff, AZ. It is a beautiful house, and the perfect solution to housing in its climate. The mass worked flawlessly since solar gain is consistent and reliable despite pretty significant seasonal temp. swings. I don't think that a pure mass system would perform very well in the New England climate though. Without some insulation to slow heat loss, the mass would be storing increasingly low grade heat. Storing heat nonetheless, but at a lower and lower temp. as the winter progressed. It seems that while thermal mass can serve the same function as insulation in the proper climate, the combination of lack of sun and periods of continuous extreme cold make thermal mass a supplement to-- rather than a replacement for-- insulation. That is, unless you don't mind your house being 50 degrees in the winter with the woodstove going.
I live in a high mass structure currently in southern VT-- it's a cellar hole with 18" thick concrete walls and 1 1/4" thick granite floor. There is 2" of blueboard-- r-10-- on the exterior of the foundation walls as well as below the stone floor. We also placed scrap blueboard as horizontal wing insulation approx. 1-2' out from all sides of the foundation to help keep the ground warm. Above our heads, we've got 1.5" iso and 3" fiberglass wrap and strap on the subfloor-- r-22. Even with this degree of insulation, our house is often a bit chilly. Its nice in that, we can go away for days without the temp. dropping significantly, and we don;t have to worry about keeping the stove going all of the time. It can go out at night and the temp. stays pretty level. That said, it tends to hover around 60 in the coldest part of winter-- fine for me, but a bit cold for most. When the stove isn;t going, it tends to feel colder than it is because the high conductivity of the masonry serves to SUCK radiance from you body continuously. When the stove is going this isn;t an issue-- a bit of radiant heat can make things comfortable. When we fire the cookstove all day, it'll get up to 70, but drops back to 60 very quickly, that apparently being its equilibrium temp. Having more mass an less-- basically ZILCH actually-- for insulation would certainly lower the equilibrium temp. to an uncomfortable degree based on my experience. I think we would do better with either more insulation, less mass, or preferably a combination of both. But then its only a cellar hole-- the real house is upstairs once its complete... someday.
