The use of the hot wire method for thermal conductivity measurement has recently known a significant increase. However, this method is theoretically not applicable to materials where radiative heat transfer is not negligible such as low-density thermal insulators. In order to better understand the influence of radiative contribution, we developed a two dimensional simulation of transient coupled heat transfer and made hot-wire measurements on low-density Expanded PolyStyrene (EPS) foams. The analysis of theoretical and experimental results shows that classical hot-wire apparatus are poorly adapted to low-density insulators. However, if an appropriate hot-wire apparatus is used, the estimated equivalent thermal conductivity is in close agreement with that estimated by the guarded hot-plate method. (c) 2006 Elsevier Ltd. All rights reserved.