EPS is the most common of the foams used and has an R-value (thermal resistance) of about 4 °F·ft2·h/BTU (equivalent to about 0.7 K·m2/W) per 25 mm thickness, which would give the of foam in a panel an R value of 13.8 (caution: extrapolating R-values over thickness may be imprecise due to non-linear thermal properties of most materials). This at face value appears to be comparable to an R-13 batt of fiberglass, but because in a standard stick frame house there is significantly more wall containing low R value wood that acts as a cold bridge, the thermal performance of the R-13.8 SIP wall will be considerably better.