Hollow foam blocks or panels that crews stack into the shape of the exterior walls of a building. They then pour reinforced concrete inside, creating a foam-concrete sandwich. The forms are left in place to provide insulation. Over 40 brands of ICFs are sold in North America, in the form of panels, planks, and blocks of various kinds. Some of these materials contain up to 85% post-consumer recycled polystyrene.
Example: Use of insulating concrete forms results in a house or commercial building that is exceptionally strong, energy-efficient, quiet, comfortable, and durable, and can be built in any style. They can also be used to construct a "safe room" inside a house. During a tornado in Oklahoma in 1999, such safe rooms reportedly withstood winds clocked at 288 mph.
