ICF houses are more energy efficient. The heating and cooling equipment can be smaller than in a CMU house. This can cut cost of the final completion of the house by an estimate of $.75 per sqft. So net extra cost is about $.25 to $3.25 according to EPS Industry Alliance.
Additional costs may come from wall thickness adding cost to window and door installations, as well as indirect cost impacts to plumbing, H-VAC and electrical installations.
Now ICF makers have developed foam bucks in the system for continuous insulated surfaces. When an ICF wall is constructed without a buck system, builders use lumber or vinyl to frame the openings for doors and windows. That means there's a gap between the framing leading to energy loss and drafty conditions. A gap
can open the envelop to moisture as well, leading to degradation of the wood framing, mold and other problems. A non-foam buck also leads to a drop in R-Value, because wood and vinyl doesn't insulate as well as the EPS foam.