We took a thermodynamic approach to building energy use, thinking not only about the quantity of energy "used" by a building but also about its thermodynamic grade. We considered that an efficient building would "cascade" its energy, using it at as many grades as possible between its introduction to the building and its rejection to the environment. In practice, this aim is hard to achieve, because much of the energy requirement of a building is for low-grade heat, but most of our energy sources are of high-grade energy.

We tried to see how these ideas could be applied in a case study of a real building, a sustainable housing development scheme in Shettleston, Glasgow. One of the issues that the thermodynamic approach highlights is the fact that we are often forced to meet low-grade energy needs with high-grade energy resources, because that is all that is available. Therefore we should either use high-grade resources that are clean and inexhaustible (like the sun), or if we are still compelled to use less desirable high-grade sources (like fossil fuels), we should aim to make the best use of them that we can. For these reasons our work concentrated on energy supply technologies.

In addition, we made a taxonomy of energy efficient technologies available now or in the near future, and we evaluated the performance of a hybrid PV against a conventional air heater.