BEEST-EB Energy-Rating Method for Assessing the Energy Efficiency of Existing Buildings

Current sustainable building rating systems typically rate the energy performance of existing buildings by assessing how efficiently they consume energy, relative to similar buildings nationwide. In these rating systems, building type and external benchmark are the two notions typically employed. Alternatively, this study explores the notions of space type and internal benchmark and develops the benchmarking energy efficiency by space type for existing buildings (BEEST-EB) method to assess the energy efficiency of existing buildings. Specifically, core research concepts such as space type, standard operation settings, standard energy consumption, operational effectiveness index, and energy efficiency score are adopted in the BEEST-EB method. An existing building usually consists of different space types, each featuring similar operational characteristics and energy demands. It is therefore proposed that, for each space type, its standard operation settings should be defined and its standard energy consumption should be estimated with energy prediction models such as eQuest, accounting for the energy effects of additional factors such as existing climate and building infrastructure characteristics. The standard energy consumption of a building, revealing the performance of its building infrastructure while operating under standard settings, is regarded as its reasonable internal energy benchmark. The operational effectiveness index of a building is further assessed by calculating the ratio of its actual energy consumption to its standard energy consumption, and used to indicate how effectively the building is operated and managed. Finally, the energy efficiency of a building is evaluated by assessing both its standard energy consumption and operational effectiveness index jointly. Only buildings having high building infrastructure performance and high operational effectiveness simultaneously are rated as highly energy efficient buildings. The Department of Architecture of the national university NTUST in Taiwan is used as a case to demonstrate how the BEEST-EB method is employed to rate its energy efficiency and used as an effective energy management tool.