The solar gain characteristics of an absorber parallel slab of Transparent Insulation Material placed between the absorber plane and the glass cover of a solar collector/storage system are investi-
gated. The transmittance of the cover system to solar beam radiation is determined by taking into account the absorption and re-ection by the slab. The sky and ground diffuse radiation transmittances are computed by a numerical technique. Steady state one dimensional conduction with internal heat
generation in the Methyl Methacrylate (MMA) slab is considered to compute the solar gain. The results are compared with such transparent insulation materials as honeycombs, double glazing and single glaz-
ing. The honeycomb cover system shows the best performance, characterized by about 12% higher solar gain than the MMA slab.