When people hear we live "underground," they make jokes about hobbit holes. They ask if our home is dark or whether mushrooms grow on our walls. But our 2,800-square-foot home, tucked carefully into the warm earth of a Vermont hillside, is bright, open and far too dry to support fungus. It is, however, topped with 18 inches of soil and grass. So, yes, I do have to mow the roof-a state of affairs that has prompted more than a few chuckles over the years.
The house was inspired by The Underground House Book, which I wrote in 1979 during the peak of the energy crisis. Why the book editor asked me to tackle the assignment is still a mystery. I knew nothing about the subject. But after I waded through piles of materials written by heat-transfer engineers, I fell in love with the idea of earth-sheltered homes. Ultimately, I decided I had to have one for myself.
I hired New Hampshire architect Don Metz, whom I'd read about in The New York Times. His own underground home in Lyme, N.H., is a monument to his wonderful sense of space, light and texture. Metz scooped the top off a hill, built his house, then replaced the hilltop. The resulting home, which enjoys unobstructed 360-degree views, feels expansive and airy, and is as beautiful as any I've seen-above or below ground. Together, we drafted a plan for my home-one that would make the house a showpiece for Metz's oeuvre: aesthetically pleasing, unintimidating and, thanks to the natural insulating effect of the earth, extremely energy-efficient.
We quickly recognized that no house could improve upon the natural beauty of our recently purchased Vermont meadow, so I asked Metz to preserve the existing landscape as much as possible. We selected a gentle, south-facing slope and began excavation. For the walls, strength was a key consideration. The north and east walls, buried deep in the earth, are standard 8-inch poured concrete. But they're reinforced with structural steel rebar every 12 inches-both horizontally and vertically. There are also several short buttressing walls that run at right angles to the main ones. Few people realize that earth can behave more as a fluid than a solid, constantly pushing against a foundation like waves breaking against a sea wall. As far as we can tell, our walls have stood firm. The perimeter of the house is also surrounded by several underground layers of perforated drain tile, which direct water away from the walls. The first line of defense against ground water is about 3 feet below the surface. The lowest is at the footings, 12 feet deeper. All of it rests in a bed of crushed stone. Once the walls and roof were in place, we pulled a warm blanket of earth back over the house and planted grass. The beefy roof structure, composed of a series of sturdy hemlock beams set 16 inches apart, is designed to support ample waterproofing-6 inches of Styrofoam insulation and about 18 inches of soil. The soil was lifted onto the roof by a large backhoe, where it was spread, raked and seeded. When it rains, the water runs off the roof, down internal drains, through pipes in the interior walls of the house, beneath the floor and onto the front lawn, just above our small pond. Despite its lawn-like appearance, the roof is never soggy after a storm.
From the moment our home was completed, it became a sanctuary for us: serene and private. It remains an intriguing place to entertain guests. The approach to the house is easy and unintimidating. Our driveway slopes ever so gradually into a hollow, and the front entrance is a traditional doorway. Visitors first enter a sunlit greenhouse with an 18-foot ceiling. Walk down two steps and around a bend (past a jungle of plants) and you've entered into the main living space, which looks out onto the pond through a glass wall. When they first enter our house, people tend to say things like, "Well, we're not really underground!" Only when I lead them to the vegetable garden on the roof do they come to appreciate the hhome's true setting.
On sunny days, the greenhouse serves as more than a bright entryway; in fact, it's the heart of the home's passive solar heating system. Our house is oriented 15 degrees east of true south to receive sunlight early in the day. The greenhouse's roof, which pierces the home's flat main roof, slants to match the elevation of the sun on January 10-statistically the coldest day of the year in the area where we live. On that day, the sun beats most directly on a wall of massive water tubes, which collect and store its warmth. Heated air is then pumped under the floor from the greenhouse to the rest of the house at night. We're never cold.
To back up the solar, we have a conventional furnace, a Vermont Castings wood stove and electric baseboard units in the bathrooms. (They've never been turned on.) I'd estimate we spend about $2,000 each winter on propane (which also fuels the kitchen stove and water heater) and burn about two and a half cords of wood in the wood stove. That's roughly half the cost of heating neighboring homes of comparable size. If we were diligent enough to "work" the house, always closing insulating window quilts at night and on cloudy days and isolating the greenhouse by closing its door as it collects heat, living here would be even cheaper than it is. But we're too lazy-and just too comfortable-to bother.
The earth itself provides all the heat we need for our oversize garage, which is designed to store three cords of wood as well as cars and toys. Dig deep enough almost any place on earth and you'll find soil with a temperature near 55 degrees. Our vehicles thaw out, dry off and start without fail, even when it's 20 below outside.
In summer, when the sun is higher above the horizon, carefully calculated roof angles and overhangs keep us in the shade. Open a window high in the greenhouse and it acts like a chimney, venting warm air and drawing cool air in through the sliding glass doors to the south. Not once have we wished for air conditioning.In 21 years, we've only had one gripe: Like many traditional roofs, ours had to be replaced last year.
After two loyal decades, it had sprung a leak. I might have ignored it, except that water dripped down inside the window directly in front of my desk. And splattered. Constantly.
The fix was no easy task. A local roofing company gave me a quote for a new, high-tech (guaranteed) membrane, which was shocking enough. Then we realized that the earth and insulation over nearly 3,000 square feet of living, storage and garage space would have to be removed by hand. (Putting even a small excavator on the roof might have risked its ending up in our bedroom.) One grueling repair job later, our new roof is watertight and we're again snug and dry. I mow the new grass about once a week in the summertime.
Roof woes aside, would I do it again? Absolutely. My house cost $90,000 to build and is now assessed at $300,000. I look forward to accumulating new energy savings in the future and to living out my days in this special house. Or at least as long as I have strength enough to mow the rooftop.