In this paper, we present a generative design approach using constraint-based programming to handle the space configuration for ceiling mounted fan coil systems in buildings. This work utilises and builds on the result from previous projects presented in Medjdoub et al. [(2003). Generation of variational standard plant room solutions. Automation in Construction, 12(2), 155–166] and Medjdoub [(2009). Constraint-based adaptation for complex space configuration in building services. ITcon, 14, 724–735.]. In Medjdoub [(2009). Constraint-based adaptation for complex space configuration in building services. ITcon, 14, 724–735], we have presented a hybrid approach using case-based reasoning and constraint satisfaction problem approach to deal with the space configuration and pipe routing of complex design problems for ceiling mounted fan coil systems in buildings. One of the limitations of the aforementioned approach is that the solution generated is defined only geometrically. In this work, we have redefined the case library by describing each case as a graph of design constraints. This new definition of the cases supports the generation of parametric solutions, where further interactive modification can be done by the user while maintaining all the design constraints. This brings benefits in terms of increasing the quality of the solution by providing the user the possibility to make the appropriate modifications using his/her heuristic knowledge. Finally, this approach has been benchmarked using real scenario design projects.