Thermal conductivity measurements at and near room temperature are presented as the basis for certified values of thermal conductivity of SRM 1453, Expanded Polystyrene Board. The measurements have been conducted in accordance with a randomized full factorial experimental design with two variables, bulk density and temperature, using the NIST 1016 mm line-heat-source guarded hot plate apparatus. The thermal conductivity measurements were conducted over a range of bulk density from 37.4 kg/m3 to 45.8 kg/m3 and mean temperature from 281 K to 313 K. Uncertainties of the measurements, consistent with current ISO guidelines, have been developed. Statistical analyses of the physical properties of the SRM are presented and include variations between boards, as well as within boards. Measurements of the foam surface roughness, microstructure, and compressive resistance are presented.