Did you ever see a driveway leading to a small hill with no house in sight? Surely there is a home beneath that soil! It’s an earth-sheltered house.
There are three kinds of homes built into the earth:
- Earth-sheltered – built into a hillside
- Earth bermed – built above ground and backfilled on north, west and east sides
- Underground – completely beneath the soil
It makes a lot of sense to build with the planet, as my Soil Science teacher put it. Soil is a wonderful insulator.
Earth-sheltered homes advantages
Soil is a constant 55° six feet below the surface. This is an easy temperature to heat and cool. It’s easier to heat your basement than the first floor of your house. Upstairs, it may be 20° outside, and say you want to heat to 65°. That is a 45° difference that you need to close.
To heat an underground space, the temperature difference would only be 10°, a much smaller difference, which would save a lot of fuel. That is the main benefit of building with the earth.
Other earth-sheltered homes benefits are:
- Pipes never freeze, because the soil does not freeze
- Strong against wind, fire, tornadoes, earthquakes
- Very little exterior maintenance
- Save land by utilizing the roof space for gardening or parking
- No insects, rodents or decay
- Great acoustics – earth absorbs sound
- Privacy – few windows
- Security – only one way out if your house is being burglarized
The drawbacks of an earth-sheltered home:
- Specialized design could drive costs up, but savings on utilities could recover those expenses
- May be hard to sell. Value may not be as high as other homes in the area
- Cannot be built in a floodplain or in permafrost
Earth-sheltered homes and passive solar heating & lighting
The south wall of an earth-sheltered home is exposed for passive solar gain. Some have a bit of the east and west walls exposed, too for light and views, but that is not as energy efficient. The north side, at the very least, needs to be covered by soil.
One perception about earth-sheltered homes is that they are dark. Skylights are installed in the roof, if possible. The south wall provides quite a bit of light. The best shape for a home like this is a dome. Light is reflected best with a curved ceiling. Heat circulates better over a curved surface, too.
An air exchanger can keep fresh air moving through an earth-sheltered home without losing any heat in winter. These homes are not stuffy! This same air circulation keeps humidity to a minimum, too.
Materials used to make earth-sheltered homes
Concrete is the best building material to create a seamless, waterproof shell. Concrete is not very earth-friendly, because it takes much energy to produce, but maybe the energy savings of the home would offset that.
Michael Reynolds, the creator of the Earthship, uses old tires for the north wall. A tire wall is just as sturdy as concrete, and stucco makes it waterproof. Both these methods save trees.
Types of earth-sheltered homes and commercial buildings
Old shipping containers could make good shells for earth-sheltered homes. The roof and sides would need to be sealed and waterproofed. Rust might be an issue if it is not sealed completely. This is my favorite idea, though! I love the idea of recycling shipping containers into usable buildings!
Forty million people in China live in yaodongs, or cave homes. They are dug out of the earth, since there is a shortage of building materials.
Earth-sheltered buildings do not have to be residential! The Dobson House, here in Taos, is an earth-sheltered bed and breakfast just a few miles from where I live. As you drive down the road approaching it, it stands out very clearly on a knoll.
It’s about more efficient energy usage
I’m a huge advocate of using earth to make a more energy efficient home. Whether a home is bermed, built into a hillside or completely underground, it will have fewer emissions and a smaller carbon footprint. That’s what we are striving for in this era of earth friendliness.