An exhaustive analysis for the determination of the urban fabric is carried out by implementing a computerized model SustArc. The model evaluates the maximum allowed 'solar volume' to be built without preventing solar access from each building and from the open spaces during a predefined period of the year. For every urban configuration, the model calculates the obtained urban density. The results show that it is possible to achieve high density urban quarters without violating any solar rights. Optimized urban fabric solutions are presented. (C) 2001 Elsevier Science Ltd. All rights reserved.