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Polystyrene home is strong, fireproof, well insulated

By Peter Tonge / October 14, 1982



Recently a test house was erected in McFarland, Wis., that can be heated and cooled for not much more than $100 a year, can withstand a torching test that leaves a conventional home in ashes, and is strong enough to support a 7 1/2-ton truck on its roof.

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The house can do all this, and yet construction costs are no more than for a conventional home using 6-inch-wide framing timbers. The secret lies in the materials used - polystyrene building blocks, plastered with Insul/Crete bonding material and held together by reinforced concrete posts - which make erecting the home a relatively simple matter.

Most important, the house should be available to homebuyers around the country within a year.

The basic building material is expanded polystyrene (similar to Dow Chemical Company's Styrofoam, which is extruded rather than expanded polystyrene). It comes in rigid board form, and should not be confused with sprayed-in-place foams, some of which have been known to give off harmful gasses after application. The Insul/Crete surface-bonding material is made of Portland cement , acrylic, and fiberglass; when plastered over polystyrene gives it tremendous strength.

The idea for the new-type home is credited to Don Peterson, an engineer with the Insul/Crete Company of McFarland, Wis. But, he says, the home ''evolved'' over many years. The company, Mr. Peterson says, first used rigid polystyrene boards to put a new facade on buildings. Old walls were covered with rigid foam boards, and a cement plaster, often in stucco form, was sprayed over that. The result: a spanking, brand-new image for an old building.

Later, when the oil embargo ushered out the era of cheap energy, it was realized that what had been looked on as purely cosmetic was also an effective insulating practice, particularly if the thickness of the foam board was increased.

During this period Mr. Peterson noticed how tremendously strong the foam board became when it was coated with surface-bonding material. What about increasing the thickness of the foam, using it as a building block rather than simply as an insulating covering? he wondered. Tests showed that the idea worked, and a 1,000-square-foot test home went up (at this writing a larger home on a suburban subdivision is under construction).

The basic building block for the new home - 4 feet long, 12 inches wide, and 8 inches high - is large, yet light enough for one man to handle with ease. As a result the walls go up rapidly, and it is this speed of erection that lowers building costs and brings them into line with conventional construction.

The building blocks are laid together much like bricks, and when the walls are complete, reinforced-concrete posts are poured in preformed holes. These tie the home into the foundation and add further strength to the walls. When complete, the building has one inch of the Insul/Crete bonding material applied to interior and exterior wall surfaces.

To test the strength of this new form of construction, a 7 1/2-ton truck was placed on the roof, where it remained for three days. In this period no cracks, sagging, or other signs of stress appeared. Pressure tests with a hydraulic press cracked and tipped wood-frame and concrete-block construction at between 500 and 1,500 pounds pressure. The foam walls covered with the Insul/Crete bonding material deflected only marginally, but did not crack at 4,800 pounds pressure.

The three completely furnished rooms were simultaneously set on fire, only to have the blaze quickly go out when the doors were closed, because of the tightness of the home. With the doors left wide open, the fire was allowed to burn for 45 minutes, during which temperatures ranged from 1,200 to 1,700 degrees F. The furnishings were totally destroyed in the fire, but the walls and ceilings - though blackened - were unscathed. During the fire the exterior of the walls remained cool to the touch, because of the high insulating quality of the walls. In fact, the walls of the home have an R factor (resistance to heat transfer rating) of 40, compared to 19 for walls in a conventional, well-insulated home; an R factor of 80 in the ceiling, compared to an R factor of 38 for the ceiling of conventional homes.

Builders around the country will shortly be licensed to build these unconventionally constructed but very conventional-looking homes. Later the owner-builder will be catered to by allowing him to erect the basic home, after which the licensed contractor will move in to apply the Insul/Crete bonding-material covering.

Much of the success of the system lies with the application of this bonding material, Mr. Peterson says, so that, at least in the near future, ''this phase of the construction must be left to licensed professionals.''

Of the new home's appearance, Mr. Peterson says: ''It will not be noticeably different, except for slightly thicker eaves and no shingles on the roof. We are not trying to develop something that belongs in fantasyland, but rather a structure that uses windows and door frames that are readily available, that fits in with existing neighborhoods, that people can be living in within the year rather than in the 21st century.''

If you are interested in more information on the new concept, write to Cubic Structures Inc., 4307 Triangle Street, McFarland, Wis. 53558.