Insulated Concrete Forms (ICF) are a high-performance, alternative forming system for cast in place reinforced concrete that can be used for walls or slabs.
ICFs used for walls are hollow core modular units dry stacked in place (simlar to Lego) and consist of two expanded polystyrene (EPS) insulating panels held together with high-strength, recycled plastic (Polypropylene) webs. The units are stacked in an interlocking pattern, steel reinforcing bars are added, the walls are braced, and the interior void cavity (4" - 12" width) is filled with concrete.
Unlike convenional wood or steel forms, once the concrete has reached its design strength, ICFs stay in place and only the temporary bracing is removed. This all-in-one system provides the:
1) Load Bearing Structure:
Reinforced concrete core provides a durable, monolithic structure that will last for over 100 years. Concrete will
never rot, warp, or be eaten by insects. ICF construction
provides superior resistance to fire, wind, earthquakes,
and other natural disasters. Another benefit of an ICF
wall system is the soundproofing characteristics. A
typical ICF wall has a sound transmission of over 50
compared to under 40 for wood-framed structures.
ICF structures boast exceptional energy efficiency and thermal resistance. The continuous expanded polysyrene forms typically provide R-Values of 30+ with no thermal bridges or gaps typical to wood frame construction. When combined with the thermal mass of the concrete, this can increase even more with temperature fluctuations inside the home being considerably minimized. Using ICFs in conjunction with other high-quality systems for windows/roofing, heating and cooling costs can be reduced by as much as 30-70%.
3) Air and Vapour Barrier:
ICFs provide a full air&vapour barrier eliminating the need for an additional plastic vapour barrier. Humidity levels are stabalized and the chance of rot or mold is eliminated. ICFs are impermeable to dust, pollens and pollution. Also, the EPS does not emit any air borne fibres typical to fiberglass insulation. ICF homes commonly quality for Enviro-home status in Canada, which is the highest possible air quality rating given to an occupied structure.
4) Substrate to directly fasten interior/exterior finishes:
The high-strength polypropylene ties in the ICF blocks extend out to within 1/4" from the exterior faces of the form. These ties are typically spaced from 6" to 8" on centre and eliminate the need for any additional stud walls or furring strips. The possibilities for interior and exterior finishes are endless. Gypsum board, siding, cultured stone and other finishes can be placed directly over the EPS panels. A single drywall screw placed in the plastic ties has been tested to provide approximately 200 pounds of pull-out resistance. Brick and stone ties can also be fastened directly to the plastic webs for veneer applications.