Foam blocks called insulated concrete forms or ICFs, offer a 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.

Four inches of ASTM C 578 polystyrene foam insulation, combined with five inches of concrete in a typical ICF system - are rated above R-17 at 75* mean test temperature. The concrete walls of an ICF home have high thermal mass, which shield the interior of a home from the extremes of outdoor temperature. This reduces both peak and total heating and cooling loads. 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. 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.

Air infiltration in an ICF Home is minimal due to the continuous air barriers provided by the foam insulation and the concrete. Likewise, there are no convection currents within wall cavities.

The high-mass walls of an ICF home not only give it a remarkably solid feel, but they also make it safer for the family. And make it a remarkably solid and secure investment, too. Concrete homes have a proven track record of withstanding the ravages of hurricanes, tornadoes and fires, when all the stick-built houses around them are in ruins.

This combination of high R-values, low air infiltration, and high thermal mass is believed to account for the amazing 25% to 50% energy savings of ICF versus wood or steel-framed homes.

In fire wall tests, ICF's stood exposure to intense flame without structural failure longer than did common frame walls. The polystyrene foam used in most ICF forms is treated so it will not support combustion. Tests indicate that ICF's tendency to transmit a flame source from outside is less than that of most wood products. [Many insurance carriers are now offering a discount on a home owner's policy for an ICF home.]

With ICF homes, there is less repair and maintenance. Polystyrene and concrete will never rot or rust. Concrete can even be exposed to the elements for centuries with few ill effects. The reinforcing steel, deep inside and protected by concrete's alkalinity, will not corrode.

ICF homes provide a healthy indoor environment, too. Nothing held within or emitted by an ICF wall is toxic. The measurement of the air contents of actual ICF houses shows an almost complete absence of any emissions.

ICF homes can be designed in any style, and will accept any traditional exterior finish including vinyl or wood siding, stucco and brick. Because custom angles and curves are easily created, it's simple to build in bows, bays and radiuses. And ICF systems accommodate any of today's most popular design features, such as tall walls, large openings, long floor spans, and cathedral ceilings.

ICFs originated in Europe (where concrete home building is standard) ICF systems have been used successfully around the world for more than 30 years. Thousands of ICF homes have been built in recent years throughout the United States and Canada. They have proven successful in every region and climate, from Orlando to Calgary. ICF systems are accepted by all the major model codes in the U.S., and by the R-2000 program in Canada.