21. The Underground House

Before I get too far ahead, I want to relate some building ideas that occurred to me while on our excursion into the interior looking at places to live. There were some really steep and rocky lots up at Altos del Maria and it would be a huge job to cut a flat for a conventional concrete block house. Why not build an underground house? It doesn’t have to be like a typical cave: totally underground with only a small door for an entrance. Instead, envision this: the excavation would be a broad opening; not one hole but a row of arched openings, each of which would be covered with a glass wall, one for every front room. These rooms include: living room, dining room, kitchen, bedrooms. The tailings from the dig would be spread out as fill for a flat front yard, with a driveway and carport to the side and trees in front to block out the neighbors if you have any within viewing range. In Altos the lots are pretty crowded, but for other locations you might not have viewable neighbors at all.

The storage, closets, bathrooms, laundry, pantry, root-cellar, wine-cellar, work-shop, sauna and meditation cave (Maharishi had once stated that such a room would be the ideal) would be dug out, one next to the other, from behind the front rooms. Their entrances would share a hallway which would run along the rear of the front rooms. These back rooms could be lit by sunlight through solar-tubes drilled into their ceilings and exiting at the ground surface above (if the crest of the hill is not too high). Or, if you are digging into a high cliff, you could use solar-colored electric lighting. Another option, if you are excavating into the side of a low hill, is to dig a well in the hilltop above and through it run a circular staircase down into the house. The top of the stairs could emerge into a cabaña that sits in the middle of your garden on the partially forested hill. That way you could have direct access to the top of your hill as well as to the side where your entrance is located.

I haven’t kept up with the technology of underground houses since the 1970’s. Back then I consulted the references in The Whole Earth Catalog and the articles in Mother Earth News while living in the woods near Takilma, Oregon. One rule of thumb should still hold true: the strongest tunnel will have a parabolic ceiling, and that shape should support itself in stable soils. How you get that shape is by bending a long piece (say 25’) of spring steel into a half circle, connect the two ends with 12’ of rope (if you want the room to be 12’ wide) and use this as a template under which to dig the hole. So the sunny house described above would actually be a row of parabolic caves, separated by columns, imagine Moorish arches!

The most important consideration in this tropical climate would be sealing against moisture because it rains so much and the ground is porous, being of volcanic origin. One economy is realized in the relative ease of digging this volcanic ground. The most obvious advantage of living underground is the constant 55° F. temperature of the earth and the resultant savings in air conditioning costs. Electricity is not cheap here. If you are very conservative and only run A/C at night so you can sleep, you could spend $100/month on A/C alone. (We use fans only and do just fine) You may want, if living underground, to leave your windows open a bit just to let in some fresh, warm air so you won’t freeze! Up in the mountains A/C may not be a consideration. You would still have humidity and if you can’t stand that you shouldn’t even live in the tropics.

While in Oregon I built a 30′ diameter 3/4 sphere geodesic dome for around $500. That expense included 2×3 wood struts, hubs with bolts, 2×12 floor joists, plywood sub-floor, wood pier foundation, shake roof and triangular Mylar windows. The interior was left unfinished. It was a very energy and materials efficient 1400 sq. ft. 2-story design. It was always cool inside when the outside was hot because it had floor-level vents that let cool air in; and there were top vents 22′ up that sucked the warm air out. The spherical space promoted rapid circular convection of the air. The cold weather advantages of this design are not relevant here. A dome uses the least amount of materials for the most structural strength and most living space. And it builds fast once you have the struts and hubs ready. Companies sell domes in pre-fabricated kits but I built mine from scratch.