The present paper, presents a computational model that assess the modification of the climatic variables in an urban context, and how they affect to the thermal performance of urban buildings. There is a clear interaction between both systems, and they are able to modify their mutual energy balances. Therefore, a coupling of the urban model and the building thermal performance, it is, absolutely, necessary if we are interested in clarify the consequences of that interaction on heating and cooling requirements, and even on urban comfort. Finally, and from the building point of view, it could be useful to develop a methodology to evaluate the impact of the microclimatic modifications in the building energy demands. In fact, it treats of a double methodology, the first one characterizes the influence of the climatic variables due to the urban context, upon the complete building, and the second upon the contribution to the demands by envelope components. (C) 2004 Elsevier B.V. All rights reserved.