Q–I saw the strangest thing today. A new house was being built using hollow foam blocks. I found out that the blocks are going to be filled with concrete. Is this method of construction substantial? Can you finish the interior and exterior as you would a wood-framed house? Are these houses well-insulated? Do you think this method of building will just be a fad?
A–You saw an insulated concrete form (ICF) house under construction. It is a fledgling industry that, in my opinion, will soar to incredible heights. Fad, you ask? The ICF method of construction is so revolutionary that I venture to say it will go down in history right next to asphalt shingles, drywall, plywood and plastic laminate. When these building materials were introduced years ago, they dramatically changed residential construction methods.
The ICF system uses insulating foam panels as a form to accept steel-reinforced poured concrete. Once the concrete hardens, this wall system outperforms standard wood-frame construction in the following categories: heating and cooling insulation; strength; fire resistance; structural pest resistance; sound-deadening; and natural disaster resistance, just to name a few. You can apply any interior and exterior wall treatment to ICF houses. Exterior wall treatment systems can be installed in the same manner as with a wood-framed wall.
There are three basic types of ICF systems, each with variations. The categories describe the way the hardened concrete looks with the foam stripped away.
One system–the flat wall– resembles traditional poured-concrete walls. Another system is appropriately called the waffle pattern because the concrete configuration looks nearly identical to the waffles I commonly eat for breakfast. The final system, classified as the screen grid, resembles an oversized window screen. With the foam out of the way, you could actually pass an object through a screen grid wall.
The foam panels and block systems contain either plastic or steel components that hold the forms together during construction. Screws or nails driven into the plastic or steel members allow you to apply wood or fiber-cement siding, brick, traditional or synthetic stucco, artificial stone, drywall/plaster or wood paneling. The manufacturers have designed the systems so that you can easily cut horizontal and vertical channels in the interior foam layer to accommodate electrical wiring and plumbing pipes.
ICF houses undoubtedly will be attractive to people who live in areas plagued by natural disasters such as wild fires, hurricanes and tornadoes. The foam used in just about every system has been treated with a fire retardant and will not support fire on its own.
Concrete is a fireproof material. Steel-reinforced concrete walls are known to withstand strong winds much better than traditional wood-framed wall systems, especially if the roof is blown off the walls. Steel strapping members can be poured into the top of ICF walls that allow more secure attachment of the roof framing than in wood houses.
Energy savings are substantial in ICF houses. The walls in most systems approach an R-factor of about 25. Some systems rate as high as R-35. By comparison, a traditional 2-by-4 wood-frame wall might have an R-factor of 13 to 17.
Air infiltration in a typical ICF house is far less than in a traditional wood-framed house. This is actually a slight negative. So little air leaks past the outer shell of an ICF house that it is almost always necessary to install a fresh air exchanger or an air duct to lower indoor pollution levels that can build up over a heating or cooling season.
An ICF house currently costs just 1 to 4 percent more to build than a traditional wood-framed home. This cost will drop as more houses are built and the manufacturing economy of scale filters through to consumers.
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Have questions about the remodeling process? Write to Tim Carter, c/o The Chicago Tribune, P.O. Box 36352, Cincinnati, Ohio 45236-0352. Questions will be answered only in the column.
For a list of ICF manufacturers and their systems, sources of excellent books and installation manuals, and other tips on ICF construction, send $2 and your name and address to Tim Carter at the above address. Ask for Builder Bulletin No. 216.
