ICF Home Builder San Antonio

ICFs 101: R-Value

What is R-Value and why is important to know with ICFs?

R-value is a measure of thermal resistance, or ability of heat to transfer from hot to cold, through materials (such as insulation) and assemblies of materials (such as walls and floors). The higher the R-value, the more a material prevents heat transfer. R-value depends on materials’ resistance to heat conduction, as well as the thickness and (for loose or porous material) any heat losses due to convection and radiative heat transfer.

ICF Effective R-Value
The Total Effective R-Value performance of ICFs consists of three factors:

(1) the R-Value of the expanded polystyrene,
(2) the thermal mass of the concrete, and
(3) the enormous reduction in air leakage (infiltration).

Insulating Value
First, the R-Value of BuildBlock’s polystyrene alone is R-20, compared to wood frame’s R-9 to R-15. So ICF walls are expected to cut the conduction losses through foundation and above-grade walls by about half.

Air Infiltration
Air leakage accounts for as much as 40% of the heat load requirements of a wood framed structure. Nothing blows through solid concrete! ICF walls reduce air infiltration by about half, compared to wood frame.

Thermal Mass
But ICF walls do more than cut down on the biggest types of energy loss. The concrete gives them the heat-absorbing property “thermal mass.” This is the ability to smooth out large swings in temperature. It keeps the walls of the house a little warmer when the outdoor temperature hits its coldest extreme, and keeps the house a little cooler when the outdoor temperature is hottest.

As a result, with the combined performance of these three factors, ICF walls actually perform as high as R-50 in some areas of the country.

Call Steve for a free consultation and get started on your new ICF custom home. (210) 559-9293.