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Superinsulated Dome

Shed, Dome, Driveway

We built our own house, this 46'-8" diameter geodesic dome. It's 1860 SF, and the surface is copper-colored Reinke aluminum shakes.

We've been spending on average about $350/year on space heat, which isn't bad considering that we're heating with electricity in a 6,200 heating degree day climate. Here's a summary of our electric bills, and a couple reasons those bills aren't even lower.

Here's a page about earlier stages of the building process, and a bunch of construction photos.

The front door and driveway:

Front Door


The living room. The flooring is Marmoleum Click, color African Desert.

Front Door


The west end of the living room becomes the kitchen:

Kitchen


The loft in art gallery mode:

Loft


Marcia hand-glazed tiles and installed them behind the kitchen sink and in the shower:

Kitchen Tiles

Shower Tiles


Steve's studio:

Steve's Studio


Marcia's studio:

Marcia's Studio


Bedroom:

Bedroom


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.

Fisheye View of Dome Interior

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 around twice the R-value of fiberglass, acts as a vapor retarder, 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 otherwise-green buildings 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.

Dome at Dusk

"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