This paper proposes a simplified model for the evaluation of the solar energy absorbed by a sunspace using an effective absorption coefficient defined as the ratio of the solar energy absorbed by the internal surfaces of the room and the solar energy entering through the glazed surfaces. Reference is made to a simple geometries constituting volumes with glass surfaces of various sizes, number and orientation. In total 10 different geometrical configurations are considered. An extensive parametric analysis is carried out by means of a simulation code with the aim of highlighting the range of variability of the absorption coefficient and the most important variables on which it depends: the latitude, geometrical characteristics of the volume, type of glass, exposure and the optical properties of the opaque surfaces. The results obtained show that the absorption phenomenon can be very adequately parameterized using the simplified models that are proposed.