I’ve been doing lot of reading lately about super-insulated net zero houses and passive solar houses. Not so different than what we had been planning to do in earlier designs, just with thicker walls. We were planning a <1400 sf passive solar house with radiant heat floor and masonry stove. But super-insulated houses with a heat recovery ventilator (HRV) only need a hair drier and a few light bulbs to keep them warm on the coldest nights. And that doesn’t take into account passive solar.
As the articles say, why spend tens of thousands of dollars on a heating system when you only need to spend a few hundred a year. If you super insulate, it makes sense to incorporate a right-sized heating system. So out with the masonry stove (sadly, I really like them) and the radiant floor (again, sadly). In with the small wood stove and some other small backup space heating system, yet to be determined.
One other major change was moving the bathroom upstairs, which allows us to organize everything under one simple roof and over one simple foundation. The walls are 12 inches thick, using double 2×4 walls with a cavity, all filled with 2 types of foam or dense pack cellulose, for an R rating of 40-50. The cold roof will have an R value of 60 to 70. We still have 4 inches of concrete on the first floor to absorb and temper the solar heat being generated by the south facing windows.
There’s still lots of work to be done. I’m studying up on all the energy calculations that I learned a long time ago in school, and I’m hoping to try out some the free tools online, like EnergyPlus. I want to make sure we don’t overheat in the winter when the sun is out, and that we can get by when there’s a few weeks of clouds. The roof overhang and thickness of the walls should keep out most of the sun in the summer.
We’re also exploring off the grid options. I want to have a ballpark number in mind for a solar power array, battery storage and generator backup, in case the estimate for getting power up to the house site is prohibitive.