Foam blocks called insulated concrete forms or ICFs, offer a new style of concrete construction for residential as well as commercial structures. These hollow blocks are pounds lighter than standard masonry blocks because they are made of expanded polystyrene - similar to the white, insulating foam used for take-out coffee cups. They either stack together like giant interconnecting, toy building blocks or are separate panels connected with plastic ties.
During construction, the forms are filled with concrete, becoming a permanent part of the wall assembly as well as adding a two-inch thick layer of foam insulation to each side of the wall. Reinforcing bars can be added for earthquake safety.
Boasting an R-value of 21 and up, foam block walls are so well insulated that manufacturers predict a home's monthly heating and cooling costs can be reduced up to 75 percent. As a result of the added insulation, the size of the home's heating and cooling system could be reduced by as much as 50 percent. The walls are fire, earth quake and termite resistant, and the layers of foam insulation provide excellent soundproofing as well as backing for drywall on the inside and stucco, lap siding or brick on the outside.
According to the Insulating Concrete Forms Association "all ICFs are identical in principle, however the various brands differ widely in the details of their shapes, cavities and component parts.
Block systems have the smallest individual units, ranging from 8" x 1'4" (height X length) to 1'4" x 4'. A typical ICF block is 10" in overall width, with a 6" cavity for the concrete. The units are factory-molded with special interlocking edges that allow them to fit together much like plastic children's blocks.
Panel systems have the largest units, ranging from roughly 1' x 8' to 4' x 12’. Their foam edges are flat, and interconnection requires attachment of a separate connector or "tie." Panels are assembled into units before setting in place - either on-site or by the local distributor prior to delivery.
Plank systems are similar to panel systems, but generally use smaller faces of foam, ranging in height from 8" to 12"and in width from 4’ to 8’. The major difference between planks and panels is assembly. The foam planks are outfitted with ties as part of the setting sequence, rather than being pre-assembled into units.
Within these broad categories of ICFs, individual brands vary in their cavity design. Flat wall systems yield a continuous thickness of concrete, like a conventional poured wall. Grid wall systems have a waffle pattern where the concrete is thicker at some points than others. Post and beam systems have widely spaced horizontal and vertical columns of concrete which are completely encapsulated in foam.
Whatever the differences among brands, all major ICF systems are engineer-designed, code-accepted, and field-proven."
The U.S. Department of Housing and Urban Development has noted builders have found that structures using ICF systems had higher costs than conventional construction -- raising the sales price between 1 and 5 percent. Construction crews needed some training but became comfortable with the new techniques by the third form-built house. The houses sold readily, and builders expected to continue using this type of construction.
Cement in the foam makes it insect-proof, and the company claims that in structural tests the wall stands up to earthquake-type stresses seven times better than a wood-framed shear wall.
For a listing of companies and more information about IFCs, link to the Insulating Concrete Forms Association.