Insulating Concrete Forms ( ICF )

Insulating Concrete Forms (ICFs) are stay-in-place formwork for energy-efficient, cast-in-place, reinforced concrete walls.
The forms are interlocking modular units that are dry-stacked (without mortar) and filled with concrete. The forms lock together somewhat like Lego bricks and serve to create a form for the structural walls of a building. Concrete is pumped into the cavity to form the structural element of the walls. Usually reinforcing steel (rebar) is added before concrete placement to give the resulting walls flexural strength, similar to bridges and high-rise buildings made of concrete (see Reinforced concrete). The forms are filled with concrete every several feet in order to reduce the risk of blowouts. The foam on either side of the forms can easily accommodate electrical and plumbing installations.
After the concrete has cured, or firmed up, the forms are left in place permanently for the following reasons:
Thermal and acoustic insulation
Fire protection
Space to run electrical conduit and plumbing
Backing for gypsum boards on the interior and stucco, brick, or other siding on the exterior