Insulating concrete form (ICF) technology involves forming the walls with polystyrene forms held together by form ties and placing concrete inside these forms. When the concrete cures, the forms remain in place to serve as insulation and attachment points for interior and exterior finishes.
August Schnell and Alex Bosshard of Switzerland were the first to develop and patent a wood fiber-cement material, which was cast into blocks. When patent rights expired in the mid-1980s, several other companies began to develop and market their systems. In 1993, when lumber prices increased sharply, the industry suddenly became more competitive in the residential market.
In 1998, 22% of people in the United States said they were aware of concrete homes. In 2000, the percentage grew to 41%.
Energy savings, protection from the forces of nature, physical security, and quiet comfort are the main promotional emphases.
The way in which ICFs are assembled is generally classified in one of three styles: panel, block, or plank. There are also three basic structural systems inside the walls: flat panel, waffle, and screen. Two types of polystyrene foam are used: expanded polystyrene (EPS) and extruded polystyrene (XPS).
Almost all concrete for ICF installations is placed with a boom pump. The usual concrete strength is 3000 psi, with maximum aggregates from 3/4 to 3/8 inch. Flowable concrete in the 6-inch-slump range, which uses low water-cement ratio mixes with either superplasticizers or mid-range water-reducing admixtures, is recommended.