The best two things a home builder/renovator can do in the name of energy efficiency is to insulate and seal a house. It's almost too bad, what with our culture's obsession with everything high tech. When people ask me about the Mill Creek NetZero Home (MCNZH), they're often expecting to hear about technology's magic answers. When I start talking about insulation levels, eyes start to glaze over, but the truth is that 75% of the difference between this house and a conventional one is that it's sealed as tight as a plastic bag and it's super-insulated.
We poured the basement slab a few weeks ago, and before that happened Peter Amerongen made sure that the slab would be in thermal isolation from the unheated components of the house. That meant laying 5" of ozone-friendly foam over the sand that we had spread over the exposed clay in the foundation hole (see picture above). Rated at R4.4 per inch, the foam will provide about an R22 insulating value. There is a special type of high-compression foam that we put over the interior footings (exposed in the pictures, under the posts), insulating the slab to about R11 from them.
So, the slab was poured onto a nice cozy blanket. This stands in sharp contrast to conventional building, where the accepted "wisdom" says that it's not worth insulating the slab from the ground AT ALL. Throughout the entire heating season, then, the dirt under the slab is constantly sucking heat from the house, wasting energy and making the floor uncomfortable. No thanks. I'll pay for a comfy bed of cush for my basement concrete, thank you very much.
[Edit]: Peter just ran the HOT2000 heat-loss simulation for the MCNZH without insulation under the slab, and it increased yearly heat loss by 20%! Incredible. We should never pour another basement slab in this country without insulating under it first.
(cross-posted at raisingspaces.com)