This photo shows the internal structure of an ICF. Note the plastic bridges that attach the foam on the inside of the form to the outside. They also prevent blow when concrete is poured into the forms. The plastic bridges provide slots into which rebar can be placed. The bridges extend through the foam and provide a nailer, a place to attach drywall or paneling via nails or screws. The foam used in most forms in expanded polystyrene. It is an oil byproduct, that is, it is made from styrene, which is one of 2,000 chemicals contained in petroleum. I am an avid supporter and practitioner of natural building, but opted for this product. When it comes to below-grade rigid insulation we don’t have a lot of choices. The plastic bridges are made from recycled plastic.
Contributing editor Dan Chiras is a renewable energy and green homes expert who has spent a lifetime learning life’s lessons, which he shares in his popular blog, Dan Chiras on Loving Life. He’s the founder and director of The Evergreen Institute and president of Sustainable Systems Design. Contact him by visiting his website or finding him on Google+.