Thermal Resistance

R-value is a measure of resistance to heat flow through a unit width of material and is expressed in m.^oC/W (hr.ft².^oF/BTU.in). Most insulation users in the United States refer to R-value numbers corresponding to customary units given in the brackets and in the figure below. R-values for soil and concrete are generally much less than 1. The ratio of R-value between a geofoam and either soil or concrete represents the thickness equivalence of the material to a unit thickness of geofoam to achieve the same level of insulation. R-values for geofoam tend to increase with density and decrease with temperature. Geofoam R values decrease or degrade with moisture absorption.