Colosol's Energy Saving Earth-Sheltered House

In 1978, construction contractor Michael Wiggins built an earth-sheltered house in Dillon, Colorado that also incorporated passive-solar features to boost its energy efficiency.

| March/April 1980

  • 062 Colosol home - house exterior
    Exterior of the Colosol earth-sheltered house. The structure's garage and air-lock entryway are located above ground. The living area is set partially below ground.
  • 062 Colosol home - interior
    LEFT: The atrium admits light into the inner sanctum of the dwelling. RIGHT: One of three Zomeworks Skylids helps to cast natural light into what would have been a dark living room corner.
  • 062 Colosol home - diagram
    The energy-efficiency of this home depends upon three major features: The heat-saving capabilities of earth-sheltering, the collection of solar warmth through the atrium and skylights, and the retention of heat in concrete, rock, and tile flooring.
  • 062 Colosol home - skylight
    LEFT: The atrium's glazing faces into the sun to catch badly needed high-mountain rays. RIGHT: Interior of room with the skylight. The home's fireplace is at the right side of the picture.

  • 062 Colosol home - house exterior
  • 062 Colosol home - interior
  • 062 Colosol home - diagram
  • 062 Colosol home - skylight

A few months back, MOTHER EARTH NEWS received a tip from reader Barry Goldberg about a passive solar, earth-sheltered house set high in the Colorado Rockies near the resort town of Dillon. Barry's description of the building — along with the knowledge that the extreme climate at the village's 9,300-foot elevation would put the energy efficiency of such a shelter to a true test — led one of our staffers to visit its builder, Michael Wiggins . . . who operates an energy-conscious contracting company called Colosol Construction.

Mr. Wiggins' subterranean shelter is located in a small development which sprawls across a high mountain meadow, but the house—with its attractive above-ground garage and entryway on the street side—doesn't appear to be out of place amidst the more conventional vacation cottages. In fact, the "normal" portion of the structure (which encompasses a total of 625 square feet) tends to obscure the low roofline of the earth-sheltered living area behind it, making the dwelling look like a tiny house with a large garage.

Mike chose to place the floor of the underground portion of the house four feet below the earth's surface . . . to allow for practical septic field drainage on his relatively flat lot. (An eight- to ten-foot-deep excavation—which would have been necessary in order to go completely subterranean — would have involved a tremendous amount of expensive backhoe work.) Then, after the four-foot-deep hole was dug, the removed earth was used to berm the walls which protrude above ground level ... creating a combination underground/earth-bermed structure.

The walls themselves are made of eight-inch-thick concrete . . . with the exception of the long living room bulwark, which is formed from hand-laid rock. All external walls are insulated with four-inch Styrofoam for the first two feet, and a two-inch layer of the same material is used everywhere else . . . even beneath the four-inch foundation slab. Furthermore, the rock wall is capped with lumber to avoid forming a heat sink between the earth-bermed wall and the upper air exposure. A total of 95 yards of concrete and 17 tons of rock went into the construction of the building . . . to provide strength and insulation.

Of course — in designing any energy-efficient building — special attention must be paid to the potential heat loss through the roof. In addition, snowy mountain climates pose what can be serious structural problems to buildings with poorly insulated ceilings. Any heating of the rooftop (caused by warmth leaking from the house) can melt the underside of what might — in Colorado's mountains — amount to as much as ten feet of snow . . . causing water to run down to cooler areas and refreeze. The resulting "ice dams" can become so heavy that they are capable of crushing a roof.

To prevent such a disaster — and to save energy — Mike built R-38 fiberglass bat into all the beamed ceilings, and R-40 thermal protection into the flat areas. Then, just to add extra insurance, he designed a ventilation system that circulates outside air underneath the roof and out the eaves. Since the roof went on the building before the snowy winter of 1979, Mike's approach has been well tested and has proved effective.

ralph wisher
7/15/2008 9:10:55 AM

interested in house plans for a house in ground approx.2500 sq. ft. i have agreat view of n. fork flathead river.need archt.or house plans

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