Solar heat gains obtainable from attached sunspaces to air-conditioned rooms are evaluated by means of the solution to the optical problem of incident solar radiation absorption through the windows and of the temperature field in the shell separating the sunspace from outdoors and adjacent spaces. The effective absorption coefficient of the sunspace was used for these evaluations as well as the ratio of the absorbed energy of the internal surfaces to the solar energy entering, and the utilization factor of the solar contributions that represent the fraction of the absorbed energy supplied to the indoor air. With reference to a pre-established geometry and to a system of windows made up of clear double-glazing, the solar gains of the sunspace and the adjacent spaces are calculated for some Italian localities at variation of exposure, optical properties and thermal capacity of the opaque surfaces, the amount of ventilation and of the shading device. Finally, the operative temperature was determined for an estimate of comfort acceptability conditions in the sunspace. (C) 2011 Elseviei Ltd. All rights reserved.