This paper deals with the empirical validation of a building thermal model, which includes a roof-mounted radiant barrier. We first present the thermal model, developed with a building simulation code prototype, the objective being to increase understanding of the thermal phenomena that govern the behaviour of the whole building. We then describe the experimental test cell, with emphasis on the details of the roof. A sensitivity analysis technique is applied to the model which shows that convective heat transfer is of great importance for the dry-air temperature of the roof air layer. The origin of the disagreement between measurements and model predictions is then identified as being due to one of the convective heat transfer coefficients. Once this is modified the agreement is found to be acceptable. (C) 2003 Elsevier Science B.V. All rights reserved.