What is an ICF?
First, a diagram showing an ICF cutaway:
ICF is an acronym for insulated concrete form, a construction method in which large hollow foam blocks are stacked to form the walls of a structure, then braced and filled with steel-reinforced concrete to create a building that is energy-efficient, environmentally friendly, and virtually indestructible.
They offer a host of benefits, such as faster construction times, lower insurance rates, and quieter interiors, but the two primary reasons behind their growth is their remarkable durability and energy efficiency.
Available under several different brand names, all ICFs consist of two rigid EPS foam panels, which sandwich a core of reinforced concrete. The concrete provides exceptional strength, durability and thermal mass; the foam provides a continuous layer of one of the world's best insulators, and is an ideal substrate for many finishes.
Energy Efficiency: The actual, real-world performance of an ICF wall far exceeds typical walls due to a combination of three factors: Higher mass, more insulation, and less air infiltration.
ICF walls have a continuous layer of expanded polystyrene foam (EPS foam) on each side of the wall. These are typically about 2 ½ inches thick per side, and rated at R-23. (If 1/8 inch of foam in a coffee cup will comfortably separate your hand from scalding liquid, imagine how well five inches of that same foam will insulate.)
In addition, the wall is virtually airtight so there's no drafts, and the dozens of yards of concrete in the walls will moderate temperature swings further. Studies have found that the ICF homes use 44% less energy to heat and 32% less energy to cool than comparable frame houses.
Durability: ICF walls protect occupants and their belongings from tornadoes, hurricanes, wildfires, car wrecks, and other disasters. They reduce long-term maintenance costs, and structures can be designed to last centuries, rather than decades. From a design standpoint, ICF technology is extremely flexible. The architecture can match virtually any style, and ICFs are compatible with all popular interior and exterior finishes.
Cost: In most areas of the country, site-stacked ICF construction is typically about 5% more than wood. Nationally, an ICF home is estimated to cost 3% to 5% more than frame building. That’s about $10,000 for a $250,000 house. With careful planning and considering the utility savings, the monthly expense of living in an ICF house can actually be less expensive. The same holds true for commercial buildings. Long-term building owners, such as schools, churches, stores, and hotels have found that when energy costs are considered, it’s actually less expensive to build with ICFs. All of the other benefits—like disaster-proof walls, quiet interiors, and less maintenance—are added bonuses at no extra cost.