Across Europe, new buildings are required to demonstrate that their energy consumption will not exceed levels set by each country's government. Both new and existing buildings, when they are sold or let, are required to have energy labels. SBEM was produced to meet these requirements. This BRE Trust Report describes how SBEM works, and gives users a practical insight into the processes and assumptions within SBEM. It describes the structure, features and methodology of the calculations in terms that match the background and experience of building services engineers and architects. The report has been written specifically for professionals who need (or want) to see behind the user interface, without going into mathematical detail.