Gary Uba and his family have gone underground—but they are not hiding from anyone or anything—especially not from the sun. Uba has built an earth berm house, apparently the only one in Denver. Tucked into a gently sloping residential lot in southwest Denver, overlooking the town of Bow Mar and the southern portion of the Front Range mountains, the Uba House is in a typical middle-class Denver neighborhood. At 2,100 square feet, it is a typically sized house with typical fixtures and appliances, but in almost every other way it is atypical.
Most important, the house, except for the front, is covered with earth, four feet of it for the most part. This, combined with its all-concrete shell, enables the structure to maintain a fairly constant and comfortable interior temperature all year round. The house is on one long and horizontal level, with arched features in the façade that hint at domed spaces within. One of the long sides faces outward, due south, with tall, large windows, allowing for passive solar heat in the colder months, as well as light penetration throughout the dwelling. The Uba House has no furnace, in-floor heating or air conditioning units. As a result, there is no ductwork anywhere in the dwelling.
The house uses only electrical power for its energy needs—lights, appliances and hot water. Seventeen solar panels in two arrays on the property (a 3.2 kW system) generate more electricity than the house uses. For each of the 18 months that the Uba family has occupied the house, Xcel Energy has rebated money to them. Far from hiding out, he welcomes scrutiny as ardently as he welcomes the sun and subsequent Xcel Energy rebates.
Seeing the Light
Uba has worked professionally in the construction end of the commercial and residential real estate fields and has long harbored a desire to build his own house. His vision was to build a forward-looking, simple, sustainable and energy-efficient middle-class dwelling—a house that is cheap to live in and one he doesn’t have to worry about when he and his family travel. After extensive research and finding a sloping house site in southwest Denver, Uba decided on an earth berm, or earth-sheltered home. Although earth berm homes can be built on a flat site, building into a gentle slope can save time and money.
The Uba House became the ultimate do-it-yourself (DIY) project. Conducting his own research on the Internet, he soon entered into working agreements with a local contractor and a company in Durango, Colo.—Performance Building Systems, Inc., which specializes in manufacturing steel framing systems for earth berm structures. Uba stayed hands-on in all aspects of the house’s development and construction.
A key goal for the Uba House was that it be cost-competitive with a middle-of-the–road, custom-built house. Obviously, there are much higher excavation and earth-moving costs that offset the savings of not having to install any heating or cooling systems or any interior structural elements. The house used fairly standard appliance packages and window packages: The windows are Low-E to let in solar heat but not UV rays. All in, at completion, the Uba House cost around $150 per square foot—meeting its cost goal.
Back to Earth
Earth berm homes have a long history. Think Mesa Verde. The generally understood definition of such homes focuses on the use of earth against three or more outside surfaces, including the roof, in an attempt to use the thermal properties of the earth to insulate the structure.
Modern materials and technology now make earth berm/earth-sheltered homes stronger, more efficient and affordable. An Internet search brings up many sites—from YouTube videos of earth berm houses being built, to articles from sources as varied as Mother Earth Magazine and the U.S. Department of Energy (U.S. DoE). There is also an Earth Sheltered Homes Facebook page.
The U.S. DoE cites these advantages for an earth-sheltered dwelling: protection from outside weather extremes, lower exterior maintenance costs, superior soundproofing and lower insurance costs due to protection from the consequences of extreme weather such as hail or wind damage. It specifically mentions the Rocky Mountain region as ideal for such homes. Negatives for these homes can be water penetration and damage and poor indoor air quality, but both can be mitigated by proper engineering and construction methods.
Gene Pearcey, the president of Performance Building Systems, the company that manufactured the steel frame for the Uba House, has been in business for more than 30 years and has been involved in the design of hundreds of earth berm houses. He got into the business because he wanted a house with little or no energy costs and marveled at comfortable temperatures in his then-current house’s underground storm cellar. When he couldn’t find a cost-effective structural frame for an earth berm house in the marketplace, he designed and fabricated his own and began marketing it. The focus is on dome shaped structures, using concrete covering a steel frame.
Like Uba, Pearcey is not an environmentalist and is not out to change the world. What he wants to do is provide an alternative type of residence that has a competitive construction price and extremely low operating and maintenance costs. The objectives are to be sensible, practical and functional. His customers have two primary motivations: energy savings from the thermal properties of soil, and safety from the consequences of bad weather and natural disasters. Most customers live in semirural or rural locations, but Pearcey has worked on numerous homes in Phoenix as well as the Uba House in Denver.
Form Following Function
The Uba House consists of three domes, half domes really, because the front half of each dome is cut off vertically to present a flat façade to the southern exposure. Looking at the house from right to left, the first dome is a two car garage, the middle dome is the main living and eating area and the last dome is the sleeping/bedroom area. The bedrooms are along the outside facing wall, not just for the direct sunlight, but for egress in case of fire. The domes are connected internally by large, long archways, providing nice transition spaces between the various dwelling uses.
When entering the Uba House, one is immediately struck by the openness, the sense of space and volume. The domes are 12 feet high with curving walls finished with stucco-like texture in a soft off-white color. There are no internal structural elements to obstruct the sense of space. There is an organic and earthy feel that is very comforting to the eye. Next, one is then struck by the quiet. The house has a peaceful lack of ambient noise due to the extreme soundproofing qualities of the earth covering the structure.
The home is anchored by a concrete floor stained the color of a mocha latte, which significantly helps retain passive solar heat coming in through the south-facing windows. Three skylights bring ambient light to the back spaces of the various domes, where functions such as a laundry and storage are located. Strategically placed large tubes, running from the interior to the exterior of the home, use thermal properties to promote air exchange and therefore prevent air quality or moisture issues.
The house was constructed somewhat like a layer cake. The foundation and concrete floor were poured first. Then the custom-manufactured steel frame was erected and tied together with standard pieces of rebar. At this point, electrical conduit was run and places for outlets and switches were identified. The frame and rebar was then covered in burlap for better adhesion of the sprayed-on concrete.
Once the concrete was sprayed on the interior and exterior of the structure, attention was paid to insulation and waterproofing. First, a waterproofing material was applied to the exterior concrete, and then the sides and tops of the three domes were covered in the first layer of earth, to a depth of three feet on the top, and to grade along the sides and back. Recycled billboard banners were added on top of this earth layer as an additional waterproofing element. Above the living and dining area is an old Burger King billboard sign; one for a casino covers the bedroom dome.
In keeping with a preference for recycled materials, used perlite panels were placed over the billboard material to enhance insulation before everything was covered by a final, foot-deep layer of earth. The structure is so strong a construction-size backhoe was used on top of the dwelling to spread and tamp down the two earth layers.
Because of its unique residential construction method, structural strength was a critical issue in the City of Denver’s review of the Uba House building plans, according to Julius Zsako, spokesperson for Denver’s Department of Community Planning and Development. He was not aware of any other earth berm houses in the city. A certified engineer with Performance Building Systems provided the requisite stamp of approval; however, as the house met all other code requirements, it was quickly approved. Pearcey claims that none of the houses designed to use his structural systems have failed to be officially permitted.
Living in the Dream
Uba has learned a lot in the process of planning, building and living in Denver’s only earth berm house. He has learned that you can build a house that has a rooftop garden, and the views can be awesome. He has learned that each of his neighbors is fine with a house that looks different. He has learned that he needs a pellet-fueled woodstove when temperatures outside dip into the single digits or lower. Mainly, Uba has learned that his long-held dream of a practical, affordable home, with almost nonexistent operating and maintenance costs, was well worth looking forward to.
Ben Bryan is the president of Owl Properties LLC, a company specializing in commercial real estate, financial services and management of complex projects.