A comparative study of benchmarking approaches for non-domestic buildings: Part 2 – Bottom-up approach

The bottom-up methods for energy benchmarking aim to derive a yardstick for energy performance based on a theoretical analysis of a building. While the top-down methods drive performance improvement by ranking a building against its peers, the bottom-up methods are focused on the building’s specific context. Consequently, the bottom-up methods can help identify how performance improvement could be materialised. These two complementary approaches can improve design practice and facilities’ management. Two bottom-up methods that could be used for energy benchmarking have been reviewed using UK schools as case studies: Building physics and aggregated end-use. The aim is to demonstrate how these methods could be used for benchmarking and identify their benefits and limitations. When all energy components are included in a model under expected operating conditions, the building physics method can be used to establish a baseline for energy performance. It is demonstrated that where this method is used under standardised operating conditions and is subject to minimum energy performance requirements, as prescribed by the Energy Performance of Buildings Directive (EPBD), it can be used to establish a benchmark for energy performance. It is also shown how aggregated end-use methods such as CIBSE TM22 can be used to define system level benchmarks, and identify the root causes for discrepancy between measured performance and design intent in a systematic way.