This paper presents a parametric study with which the factors and variables involved in determining beam, diffuse and reflected solar gains for the glazed parts of any saw-tooth roof can be estimated. The developed model has been applied to significant cases of saw tooth roofs facing the equator, obtaining some annual reference patterns for these factors and variables aiming to estimate the suitability of the adopted configuration and focussing strategies as means for obtaining a seasonal control of the solar gains on the roof apertures. The starting point of this study has been an actual case consisting in the refurbishment of a open courtyard by installing an innovative roof which, apart of other solar features as the integration of PV modules and a device to promote natural air movements, it has been designed to maximise solar gains during the winter months and minimise them in summer to reduce the corresponding space thermal loads. (C) 2003 Elsevier Ltd. All rights reserved.