Insulated Concrete Forms [ICF]

Insulated concrete forms are made of blocks of polystyrene foam or other rigid insulation connected together with space in between for pouring a concrete wall. ICF can be used for foundation walls and above-ground walls.

Works for the construction of new walls, not so practical for retrofitting. Look for the highest R-value of the insulation layers, which typically maxes out at R22 for ICF. This is not high enough for a super-insulated house, but the designer/builder can always add an additional layer of insulation to the outside. Check what kind of foam the ICF is made of - expanded polystyrene is a good choice, with low VOC emissions and low global warming potential.

It provides a durable, well-insulated, airtight, and sound-dampening wall with no thermal bridging (it's insulated entirely on both sides). On the downside, concrete takes a lot of energy and emits high greenhouse gases in its production.

Werner Gregori, a Canadian contractor, filed the first patent for an insulated foam concrete form in 1966.