Even for someone with average construction skills, the panels of America Solartron Corporation's prefabricated plywood house are easy to assemble. Note the drainage system set outside the perimeter of the foundation.
PHOTO: TERRI CALVERT/AMERICAN SOLARTRON CORPORATION
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
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
"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
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
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
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
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
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
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"
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"