SEMPER, which was originally developed at Carnegie Mellon University (CMU), is an active, multi-domain, space-based, object-oriented design support tool for integrated building performance computing. This paper discusses the key findings of a collaborative research project between National University of Singapore, Carnegie Mellon University and Temasek Polytechnic to modify and transform SEMPER prototype 1 into SEMPER-II (S2), as an internet-based computational design support environment in order to facilitate geographically distributed design collaboration. The working details of the multi-domain Thermal Suite within S2 and the integration of the S2 GUI with a CAD tool are specifically discussed with illustrative case studies.