Life cycle environmental benchmarks for Flemish dwellings

To reduce the environmental effects caused by building construction and operation, life cycle assessment (LCA) is increasingly applied. In recent years, national building regulations have implemented LCA requirements to support building life cycle impact reduction. A key element in these regulations are environmental benchmarks which allow designers to compare their building designs with reference values. This study aims to develop bottom-up life cycle environmental benchmarks that represent the range of environmental impact results achieved with conventional construction in Flanders, Belgium. For this purpose, the study investigates the potential of using a database of building energy performance calculations. Specifically, this study considers 39 residential buildings identified as representative of the Flemish energy performance of buildings database of 2015–2016, applying modifications to establish scenarios that are still relevant in 2025. The buildings are assessed with the Belgian LCA tool TOTEM to calculate an aggregated environmental score based on the European product environmental footprint (PEF) weighting approach and including 12 main impact categories. In addition to the aggregated score, the climate change (CC) indicator is analysed individually. In view of the benchmarks, variations were applied to the 39 original buildings in terms of heating system and materialisation. The variation in heating system included changing gas boilers to electric heat pumps to comply with upcoming (2025) Flemish building regulations. The variations in building materials included three sets of conventional Flemish building element compositions that were applied to generate a wider spread of impact results as a basis for benchmarks. Benchmark values were derived through a statistical analysis of the 117 modelled variants: a best-practice value (10th percentile), reference value (median) and limit value (90th percentile). For the environmental score, the benchmark values are 86, 107 and 141 millipoints per square meter of gross heated floor area (GHFA) (mPt m ^−2 GHFA), respectively; and for CC, the benchmark values are 844, 1015 and 1284 kg CO _2 -eq m ^−2 GHFA. Finally, the study discusses the representativeness, implications and limitations of the final benchmarks and benchmark approach.