Regarding the comparison between the computed simulation of sunspaces solar gain computation, this work represents a contribution to several studies that have been made in the last years [M. Wall, Distribution of solar radiation in glazed spaces and adjacent buildings. A comparison of simulation program, Energy and Buildings 26 (1997) 129-135; M. Wall, A design tool for glazed space: Part I. Description, ASHRAE Trans. 101 (1995) 1261; B. Fredlund, A design tool for glazed space: Part II. Examples, ASHRAE Trans. 101 (1995) 1272]. In particular, utilizing a calculation program carried out just for Mediterranean bioclimating buildings (Method 5000) and the calculation procedures of the Italian Norm (Method Law 10/91), some analysis have been made. The results have been shown that for the solar gain, the Method 5000 is precise and it has been shown that as the thermal inertia of the buildings increases, the results of the two methods are similar. From the results, it is also possible to confirm that in the Mediterranean climates, the energetic requirement in well insulated buildings can be reduced in half by utilizing passive solar systems. (C) 2000 Elsevier Science S.A. All rights reserved.