We show here an adaptation of the classical Flash Method permitting the measure of the thermal conductivity of semi-transparent
porous materials. A flash lamp send a heat pulse on the upper face of a cylindrical sample and lower face temperature is analysed.
The semi-transparent material is sandwiched between two copper slices. The sample used scatters thermal radiation, and absorbs
it very little. It is therefore possible 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 flux
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 coefficient qualifying the thermal exchange
between the sample and the environment during the experiment.