ICF’s are forms for poured concrete walls that stay in place as a permanent part of the wall assembly. The forms are made of High Density foam insulation and are pre-formed interlocking blocks connected with plastic or metal ties. The left-in-place forms not only provide a continuous insulation and sound barrier, but also a backing for drywall on the inside, and stucco, lap siding, or brick on the outside.
"Flat" systems yield a continuous thickness of concrete, like a conventionally poured wall. "grid" systems have a waffle pattern where the concrete is thicker at some points than others. "Post and beam" systems have discrete horizontal and vertical columns of concrete that are completely encapsulated in foam insulation.
ICF Direct can recommend a system, but the most popular is a "Flat" system that produces a continuous thickness of concrete, like a conventionally poured wall with 2.5" of insulation on both the inside and outside of the wall. These ICF systems are engineer-designed, code-accepted, and field-proven.