Earth-sheltered and underground homes are certainly nothing new to MOTHER EARTH NEWS' readership. After all, this magazine has been touting the advantages of such dwellings (low fuel costs, minimal maintenance, and superior durability to name a few) for some time now.
Recently, however, we've come across a new concept which might just alter the course of the whole "underground" movement: the prefabricated fiberglass house!
As most of us already know, the great majority of subterranean dwellings are at present made of concrete, poured into forms that have been carefully set into excavations. However, while this method does assure a rock-solid structure, the entire process can be expensive, and often forces the owner to hire a professional work crew to achieve satisfactory results. Not only that, concrete—because of its porous nature—must be thoroughly protected from the effects of moisture ... which will tend to seep through even the thickest of slabs and can actually deteriorate the cement-and-sand mixture.
But now after two years of research, Ralph Bullock (of American Solartron Corporation) has come up with an alternative to the usual underground building materials: his "answer" is fiberglass!
Strange as it may seem, Ralph wasn't looking for a concrete substitute when he made his discovery. In fact he had set out to develop and market a low-cost alternative to "standard" subterranean construction. His idea was to precast concrete slabs and join them together at the building site to form a "finished" structure.
Upon investigation, though, Mr. B. discovered that a prefabricated concrete home just wasn't feasible: "It was far too heavy to transport in sections, and even worse, the finished house would have been overly expensive. That's when we decided to try other materials." The "other material" that Ralph settled on was fiberglass, which is strong, inexpensive, lightweight, water resistant, fireproof, non biodegradable, and known for Its terrific insulative properties. Furthermore, this amazing substance has—for years—been used successfully in the manufacture of septic tanks, sewer lines, boats, and railroad cars—applications that demand a high degree of durability.
Of course, the individual "Solartron" panels are not made up of fiberglass alone. Instead, a section of 5/8" construction-grade plywood that measures 8' X 9'4" is "framed out" with 2 X 6's, which are glued and nailed on 16" centers and also fastened around the board's perimeter. Then the entire assembly is laminated with Hetron 92 FS (a fire-retardant resin) and covered with layers of fiberglass and resin alternately till a panel thickness of 7 1/8" is eventually achieved. Finally, a fine-mesh fiberglass veil is laminated to the exterior of the wall to guarantee a virtually waterproof outside surface.
"Building Block" Construction
Because the wall components only weigh 300 pounds apiece (and the larger roof sections 500 pounds), each Individual segment is a real featherweight when compared to its concrete counterpart. And—due to the fact that the panels are designed to interlock (through the use of tongue-and-groove or shiplap joints)—a standard 1,231-square-foot (exterior dimensions) home can be constructed in about eight hours by an experienced work crew once the excavation is finished and the foundation footings are laid.
To assure full water-resistance, the roof sections are "glued" to the upper edges of the walls with a bead of pliable silicone sealant, and the completed "cube" is covered with a solid piece of heavy-duty, 6-mil plastic sheeting. Next, round river rocks 3/4" to 1 1/2" in diameter are poured over the entire structure to a depth of two feet on the sides and four inches on the roof, creating a "drainage layer." In addition, the roof is convex (to shed seepage and prevent the accumulation of standing water), and a network of drains is installed around the building's foundation.
Finally, a layer of earth—between two and three feet thick—is placed on top of the fiberglass "box." If the dwelling is only partially underground, additional soil is bermed up against any protruding portion of its walls (with the exception of the front of the house, which is fully exposed). Once this is done, grass and shrubbery can be planted over the entire earthen cover to stabilize the soil and add aesthetic appeal to the residence.
The Test of Strength
Naturally, one of the most important concerns in any subterranean house is structural strength. After all, statistics show that three feet of soil when covered with a foot of snow will exert 360 pounds per square foot of pressure on the surface below.
A Solartron roof panel, however, is rated to support a pressure of 550 pounds per square foot, and in fact was proven — by an independent testing laboratory — to remain intact under a total surface load of 23,038 pounds ... with a deflection of only about 1/2' in the center of the panel. And the wall components are even stronger: Test results show that those panels can withstand an amazing 183,000 pounds before ultimate failure! So, regardless of what the skeptics say, earth-covered dwellings are actually a good deal safer than conventional homes ... and are, of course, especially resistant to storm damage or vandalism.
It Saves Money Coming and Going
Since the idea of prefabricated, modular earth-sheltered homes is relatively new (as is the entire "underground living" concept), you might expect such a home to carry a hefty price tag. Fortunately, however, the cost of building a Solartron house is equal to (and in some cases less than) that of erecting a conventional aboveground structure, with the final "tab" averaging out at about $40 to $45 per square foot depending on location, type of soil, and depth of excavation.
But that's only part of the story. The real savings come after the house is built. Because it's protected by a layer of earth, the fiberglass home is reluctant to give up its heat and actually absorbs a good deal of thermal energy from the soil around it (which—below the frost line—remains at a constant 55°F all year round).
In order to have an accurate "yardstick" with which to measure his home's thermal efficiency, Mr. Bullock asked the local power company to supply him with estimated annual energy consumption figures for heating and cooling his "model" Illinois residence. Ralph found that—even with the terrific loss of heat resulting from the coming and going of some 15,000 interested people who visited the dwelling during its winter-of-1978 open house—his actual utility costs during the cold month of December were only $15.75. And, using that figure as a reference, the power company "guesstimated" that such expenses for an entire year wouldn't exceed $128!
It should be remembered, too, that these energy-use "tests" were made in a residence with an open courtyard. if the patio had been closed in (a Solartron option), the amount of cash saved would have been even more significant! Furthermore, considerably greater savings could be realized with the installation of an efficient woodburning stove; the already low utility bills might even be cut in half!
The Solartron home is "thrifty" for other reasons, too. Exterior maintenance on the structure is kept to a minimum because only one wall is exposed (and even that is partially covered with a rock facade to reduce periodic upkeep). Insurance rates are also lower for "underground" dwellings. One guarantee firm in the Land of Lincoln presently offers a 25% premium reduction for earth-sheltered abodes, and others are estimating that the figure could reach 40-45% in the near future. Furthermore, the Illinois Insurance Commission soon hopes to approve a 33% rate cut on all fire policies underwritten to owners of subterranean homes. (Similar benefits are already available or should soon be offered all over the United States.)
And That Ain't All ...
The new American Solartron home is—obviously—far superior to a conventional above ground structure, but it also compares very favorably with its subterranean "cousins." Adequate ventilation is provided through a duct system, and—if you study the floor plan—you'll see that every room in the building is equipped with a window that will admit natural light thanks to a courtyard which is bathed in sunshine throughout the course of the day. This source of daylight guarantees that the fiberglass dwelling is not stuffy, dark, or damp. In fact, it might just be a whole lot brighter than some "exposed" houses.
The courtyard provides other advantages, too: If it's left open to the outdoors, it acts as a fresh air patio and additional ventilation source. (With the addition of a stairway, the open area can also function as an additional entrance/exit.) On the other hand, by simply installing a series of roof joists and covering them with glazing or plexiglass to close in this veranda, the owner could create an effective solarium, lounge, recreation area, or greenhouse/hydroponic garden (not to mention the fact that the additional insulation gained by the use of such a roof will help to "temper" the home's atmosphere).
Furthermore, because of the "modular" design of the house, there are numerous variations on the "theme" presented here. You'll note that each room is 12 feet in width for proper support of the roof panels. As long as that dimension is allowed for, the various chambers can be arranged in any number of ways to permit an almost unlimited diversity of style.
In fact, the Solartron people now have several hundred designs and floor plans available that they hope will cover the spectrum of potential customers' needs. These blueprints encompass split-level and two-story styles, and even include patterns for hotels, motels, and office buildings.
You Can "Do It Yourself" and Save
In contrast with many other earth sheltered dwellings which are custom designed, custom-built, and carry an equally "custom" price tag, Ralph Bullock's package is just the thing for a buyer who wants to take part in the building of his or her house. Ralph has done all of the "homework," and his panels are ready to be dropped into place on their concrete footings. This prefabrication, of course, opens up a whole new world of possibilities to the prospective owner. For the first time, someone with only "fair to middling" construction skills can tackle and successfully complete what would normally be a "professionals only" job. Even if the concrete foundation work had to be handled by a contractor, the owner could still save 20% or more of the total cost of construction by simply assembling the home him- or herself. (Of course, the use of heavy equipment is still necessary, but since the basic structure will be completed in one day, rental costs for such machinery can be kept to a minimum.)
In addition, the Solartron folks provide a fully detailed set of instructions and blueprints with each design they sell, and make themselves available after the sale to help with any technical or construction problems that the builder might run into during the course of an installation.
Finish carpentry poses no problem either. The fiberglass component parts are designed so that inside walls, and door and window openings, can be "dressed up" just as in any conventional home. The owner/builder has the option of either paneling, painting, or plastering the interior surfaces, and installing the hardware of his or her choice.
And There's More to Come!
The Solartron people are busy setting up distributorships that they hope will eventually serve all of the U.S., from coast to coast. At the same time, though, they're working on new designs which will not only supplement their already comprehensive line of offerings but will also give the Solartron houses an added dimension: "sun" heating for 100% energy self-sufficiency! If all goes as planned, within two years Mr. Bullock will have solar capacity incorporated into all the structures he sells.
Until then, though, the numerous other advantages of Solartron's earth covered shelters should be reason enough to warrant a long, hard look at what Ralph Bullock has to offer. You might just end up "goin' underground" yourself!
More Subterranean Sources
If you'd like to know more about earth-sheltered homes,
consult the following articles from this publication.
1. "Andy Davis: Earth-sheltered House Builder"
2. "David Wright: Passive Solar Design"
3. "The Paul Isaacson Family Lives In The House Of The Future"
4. "See! Passively Heated Underground Houses Can Be Beautiful Too!"
5. "Go Underground in Michigan"