Over this period his primary research was on the role that energy systems simulation could play in helping to reduce energy demand, accelerate the take-up of renewable energy technologies, mitigate environmental impacts and improve human well-being. He has led or participated in many UK, EU and other international research projects. A key aspect of his research involved the development and dissemination of software tools for energy systems simulation, and support for the application of these tools in design, research, teaching and policy-making contexts. Under the supervision of Prof. Tom Maver, Joe created the ESP-r building simulation program as the core of his PhD thesis, which is still used worldwide. Joe has supervised dozens of PhD students, many of whom contributed to the further development of ESP-r and are now themselves prominent in the inteenational building simulation community. He is a founder member and past President of IBPSA the International Building Performance Simulation Association, which promotes building simulation worldwide.