Insulated Concrete Forms (or ICF's) are forms that are built-in insulation that accepts reinforced concrete. These large hollow blocks are stacked like legos and filled with reinforcing bar & concrete. In the end, you are left with a structurally sound wall that is insulated with a vapor barrier and is ready for final exterior and interior finishes.
There are three general types of ICF construction: flat ICF wall (as shown in the photo above), where the poured concrete surface is flat; waffle grid, where the concrete has varying thickness; and open grid, where the concrete forms a grid.
Based on research conducted by the National Association of Homebuilders Research Center, this publication reports on the results of testing and monitoring done on three homes built in Chestertown, Maryland. The homes, each 1,200 sf, were identical, except for the construction of the exterior walls. Two of the homes were built with insulating concrete forms, the third with conventional wood framing. Results from extensive cost and material analysis, acoustic testing, and energy usage are described. The ICF homes cost 3 to 3.5% more to build than the comparable wood frame home, based on the sales price of the home. The concrete homes were significantly quieter, testing to a Field Sound Transmission Classification as height as 42, compared to only 34 for the frame home. Energy usage in the concrete homes was approximately 20% lower than the wood frame home. This report demonstrates the superior performance and value achieved in concrete homes at a modest increase in the overall cost of the home.