We built our own house, this 46'-8" diameter geodesic dome. It's 1850 square feet, and the surface is copper-colored Reinke aluminum shakes.
The dome has no furnace, and the solar-heated radiant floors are a recent addition. For the first six winters, this was our heating system:
Two 1500 watt space heaters kept us warm in the coldest weather. We were averaging around $365/year on space heat, which isn't too bad for a house this size using electric resistance heating in a 6,200 heating degree day climate. To put that in perspective, a few years ago we went to the nearby open house of a just-built LEED Platinum home with identical square footage. Its projected space heat budget was $450/year using natural gas, which is typically a much less expensive way to heat.
Here's a summary of our electric bills before we added the solar. They should be substantially lower in the future.
The front door and driveway:
The living room's flooring is Marmoleum Click, color African Desert.
The west end of the living room becomes the kitchen:
The loft in art gallery mode:
Marcia hand-glazed tiles and installed them behind the kitchen sink and in the shower:
So why a superinsulated dome? I've always loved the looks of domes and the feel of their interior space. The fact that they're stronger and offer less wind resistance was also a factor. Domes typically survive tornados and hurricanes that destroy an area's rectangular houses.
As far as energy efficiency, a sphere encloses maximum volume with minimum surface, so for a given volume of space a dome will have less surface area through which to lose heat. Some of the dome's volume may be inaccessible, but it's still like getting beautiful high ceilings with no energy cost penalty.
We used the Natural Spaces hub system, which makes double-wall construction easy. The dome shell can be designed to hold whatever thickness of insulation you specify.
Add enough insulation to a well-sealed house and you eventually reach a point where ambient heat sources are enough to keep the place warm. That's the basic idea behind superinsulation. Houses are full of electric lights, appliances, computers, people, pets -- all of them throwing off heat. South windows let in warmth from the sun. In a conventional house, all these sources are trivial compared to how much heat is pouring out the walls. A superinsulated house loses heat so slowly that these incidental heat sources are enough to keep the place comfortable much of the year. The amount of extra heat needed in winter is so small that it can be cheaper to heat with electricity than to install, maintain, and periodically replace a furnace.
When building the superinsulated house, the cost of the extra insulation and airtightness can be at least partially offset by the savings from not having to include a furnace or a complex heat distribution system. Because the house is so well sealed, a heat-recovery ventilator is a good idea. That's a device which uses heat from the outgoing stale air to warm up the incoming fresh air. The most efficient models also capture latent heat from humidity and are known as energy-recovery ventilators.
I opted for spray-in-place polyurethane foam insulation because it has a high R-value and does a superior job of stopping air infiltration. It's expensive up front, but saves money in the long run.
Foam hasn't always been the most environmentally-friendly building material, but that's starting to change. It no longer needs to use gases that are damaging to the ozone layer. Earth Foam, the brand we used, is made largely from castor beans. In any case, it seems like a reasonable trade-off to use a few petroleum-based materials in the construction phase if it means using much less energy after that. Many homes that are green in the sense of using building materials closer to nature still consume conventional amounts of natural gas every winter, year after year, forever. Which house is greener over the long haul? I'd say it's the one with all that foam in the walls and no chimney.
"Call it the groove factor, call it the hipness quotient... there is a timeless,
future-primitive chic to the geodesic that few houses offer. The dome concept appears to be erected
on the improbable intersection of hippie culture and the space age."
-- Matt Jones, Independent Online