We investigated the relationship between thermal conductivity, specific heat, and temperature conductivity of fused silica ceramics with a true porosity of 1.5–28%, and temperature. Above 500°C we detected a sharp deviation in the thermal conductivity of fused silica ceramics from this factor recorded for fused silica. The deviation is explained by the presence of straight-through radiant heat currents during the tests of the fused silica. We established a linear relationship between static and dynamic elasticity modulus and porosity, but could not detect a relationship for temperature. We investigated the relationship between the most probable bending strength value and porosity. This relationship can be described by the exponent with an accuracy of up to 4%.