In the present work an effort will be made to analyze the radiation exchange in enclosures with boundary walls partly transparent to long wave thermal radiation. The objective of the analysis will be to provide a general set of equations describing the radiation exchange between the boundary of the enclosure, the sky and other distant objects when the boundary walls of the enclosure have asymmetric radiative properties and an arbitrary transparence at long wavelengths. The governing equations are sufficiently general to account for surrounding surfaces of an arbitrary number and separately for the radiant heat fluxes exchanged between the boundary of the enclosure and the surfaces surrounding it within and outside the 8-14 μm atmospheric window band. The proposed method is shown to be in good agreement with experiments using a radiating surface covered with polyethylene under solar radiation incidence, as well.