This paper presents generalized formulations for the calculation of the solar transmittance of symmetrical configurations like square celled honeycombs as well as for such convection suppression devices(CSDs) are parallel slat arrays,wherein propagation of the incident ray is a strong function of solar azimuthal angle. The formulation take into account refraction, scattering and absorption of radiation by vertical walls. The validity of the formulations is examined by experimental observation made with a pyranometer which show good agreement. Honeycomb and slat arrary transmittance to incident radiation is calculated,and results correspondings to a wide range of angles of incidence and aspect ratios are presented. It is found that a slat device made from thin transparent film may have solar transmittance in the range 0.9-0.95. However, it seems essential that the device by encapsulated for satisfactory performance.