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Briefing: ICF Construction

ICFs have many advantages over wood frame construction

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Hollow foam ICF blocks fit together snugly to form a wall; the wall cavity is then filled with cement.

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ICFs, or insulating concrete forms, aren't the new kid on the block -- they've been around since the 1960s -- but many Americans are still unfamiliar with ICF construction. Take a look at the many advantages of the green building technology known as ICFs.

ICF Building Basics

An ICF block looks like a hollow panel of white foam, roughly the size of a suitcase. ICFs are commonly made of polystyrene foam (a.k.a. Styrofoam), though they can also be made of soy-based polyurethane foam or other materials.

The ICFs -- which are designed to lock together to form a tight seal -- are easily stacked to build a wall. Openings for doors and windows are framed using wood or other material, and steel rebar is commonly added inside the hollow ICF blocks for added strength, particularly in areas where high winds or earthquakes might be an issue.

After the wall is built and supported by temporary scaffolding, concrete is poured from the top of the wall into the hollow cavity within the ICFs. After the concrete is poured and set, any kind of roof system can be constructed atop the ICF walls. Siding -- wood, vinyl, stucco or other -- is easily attached to the inside or outside of the wall. (The ICF material acts as a moisture barrier, so additional moisture barriers aren't needed.)

ICFs easily accommodate plumbing, electrical and other conduits. When completed, an ICF building looks just like any ordinary wood-frame building -- but it acts very differently.

Benefits of ICF Buildings

Compared to standard construction using wood or metal framing, ICF construction costs around 5 percent more. Many homeowners and commercial building operators, however, realize that this minor up-front cost pays for itself rather quickly -- in most cases, the payback period is 3 to 5 years.

Energy efficiency is a primary benefit of ICF construction and the reason for its quick payback period. The insulation value, or R-value, of ICFs is significantly greater than wood-frame walls: ICF walls generally have an R-value between 15 and 20, whereas wood-frame walls have R-values between 10 and 15. Moreover, wood-frame walls also suffer from thermal bridging where uninsulated studs leak heat to the outside -- because they have no studs, ICFs don't leak heat through bridging.

ICF buildings are, therefore, very green buildings. According to ICF manufacturer ECO-Block, "Energy savings generated by an ECO-Block building are up to 50 percent, and HVAC tonnage requirements reduced by as much as 30 percent -- and continue for the life of the building."

Besides the long-term energy savings, costs can also be cut during construction, since ICF walls are quicker to erect than wood-framed walls. Smaller heating and air-conditioning units are needed, too, resulting in additional savings. And depending on the location, ICF buildings may qualify for green tax credits or other incentives, lowering costs even further.

Other benefits of ICF construction include quiet: ICF walls have sound insulation that's roughly 30 percent higher than standard insulation and drywall construction. Though they're not completely fireproof, UCF walls have up to a four-hour fire resistant rating. And termites and other wood-boring pests can't eat through an ICF-and-concrete wall, unlike a wood-stud wall (though termites can live in ICF foam).

ICFs: Green, or Greener?

Despite their many advantages, ICFs aren't perfect, nor are they perfectly green. Polystyrene foam is a petroleum-based product that's non-renewable, so right off the bat any green credentials are considerably diminished.

Portland cement, steel and other ICF materials have similar non-green credentials. And despite claims that insurance companies love the fire resistance and other characteristics of ICF construction, critics have found that many insurers don't offer any discount for ICFs (partly because they're so new, especially in the United States).

Other claims, such as the health benefits resulting from a wall that has no cavity and therefore no space for mold and mildew to form, are difficult to substantiate. Common sense, however, would indicate that a solid wall of poured concrete would be more resistant to mold, and to high winds and other structural damage, than a wood-frame-and-insulation building.

For more information on ICF construction, visit the websites of ECO-Block, ARXX ICFs, and the ICF Builders Network.

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