We show here an adaptation of the classical Flash Method permitting th
e measure of the thermal conductivity of semi-transparent porous mater
ials. A flash lamp sends a heat pulse on the upper face of a cylindric
al sample and lower face temperature is analysed. The semi-transparent
material is sandwiched between two copper slices. The sample used sca
tters thermal radiation, and absorbs it very little. It is therefore p
ossible to account for two parts of heat transfer through the material
: a pure conductive phenomenon and a radiative one. In most insulating
materials radiative transfer represents about 1/3 of the total heat f
lux at the ambiant temperature. The problem is solved with electrical
analogy, quadripoles technique and Laplace transform. The modelization
brings out two physical character parameters of the material and a co
efficient qualifying the thermal exchange between the sample and the e
nvironment during the experiment.