The article presents the results obtained during investigation of thermal conductivity of expanded polystyrene slabs at mean temperature of 10 degrees C and within interval of temperatures from 0 degrees C to 50 degrees C. Slabs of types EPS 50-EPS 250 with varying density from 14 kg/m(3) to 38 kg/m3 were subjected to investigation. The nominal thicknesses of slabs were 50 mm and 100 mm. Measurement of thermal conductivity was performed in conformity with requirements of ISO 8301, EN 12667, EN 12939 by the use of device FOX 304 (Laser Comp., USA). The empirical equations were suggested for determination of thermal conductivity at mean temperature of 10 degrees C, basing on the results obtained at determination of density of expanded polystyrene slabs with thicknesses of 50 mm and 100 mm, as well as the regression equation was presented to describe the impact of thicknesses of slabs within interval from 50 mm to 100 mm on coefficient of thermal conductivity at mean temperature of 10 degrees C. The empirical relationship was found for conversion of thermal conductivity at mean temperature of 10 degrees C to temperatures within interval from 0 degrees C to 50 degrees C. (C) 2012 Elsevier B.V. All rights reserved.