In this paper we discuss progress that has been made in modelling of urban resource flows to support urban designers to optimise the sustainability of their design and planning proposals, In particular we consider models of urban energy demand and more general resource flows. We also critique this and from this discuss work that is underway to improve the scope of more complete resource flow models as well as probability with which users will be able to identify optimal configurations of available parameters describing their urban models. Finally we conclude by discussing ways in which building models could be coupled with models of land use and transport interaction for more complete prediction of urban sustainability and how this might evolve with time.