Walls made of ICFs perform, on average, like a wood-frame wall with R-30 insulation. The equivalent R-value of ICFs is determined by three key factors: First, the R-value of the expanded polystyrene. Second, the thermal stability of the concrete walls reduces temperature fluctuations, lowering heat load requirements compared to wood-frame buildings. Finally, air leakage (infiltration) accounts for 20-40% of the heat load in wood-frame buildings, but ICFs eliminate this air infiltration. Combining the R-value of the expanded polystyrene, the thermal mass of the concrete, and the reduced air infiltration, ICF walls can perform as high as R-40—or even more in certain regions.
