Multiscreen insulations, which consist of highly reflecting foils separated by a fibrous insulation, are being studied for space applications. For design purposes the heat transfer mechanisms through absorbing, emitting and scattering porous materials must be understood and efficient tools for analytical temperature predictions are required. In order to calculate the heat fluxes through evacuated fibrous insulations, different methods are explained and compared. Consideration is given to a one-dimensional system of two parallel, diffuse gray plates, which are separated by a fibrous insulation. The coupling of solid conduction and radiation is specially taken into account.