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Over recent years Belgium has made meaningful effort in adopting Life Cycle Assessment (LCA) in building practice to improve building environmental performance. Today, architects can compare the environmental performance of different building designs with an online calculation tool that incorporates the national LCA method. However, they are still lacking environmental benchmarks to position themselves within current building practice. Furthermore, such benchmarks play an important role in the development of environmental targets in building regulation. In this research, benchmarks are defined for new residential buildings in Belgium. A bottom-up approach is followed consisting of a statistical analysis of reference buildings to define limit, reference and best practice values. The buildings are based on four representative typologies for Belgium, ranging from detached houses to apartments. Different variants are assessed including various energy performance levels and construction types (solid versus timber). The buildings’ life cycle impacts are calculated including the embodied (material) and operational (energy) impacts. Results are reported both for an aggregated environmental single-score and for Global Warming Potential (GWP). The calculated reference values for life cycle and embodied GWP (20 and 7 kgCO2eq/m2.year) are comparable to existing benchmarks in the literature. The results further highlight that building compactness provides the largest impact reduction, followed by construction type. Finally, limitations are discussed and recommendations are formulated for developing future benchmarks.

Building construction and operation both have a high environmental impact. In Flanders (Belgium), public authorities have defined clear targets for improved building energy performance, but a strategy to reduce construction (embodied) impact is still lacking. Environmental benchmarks based on Life Cycle Assessment (LCA) have been identified as a means to limit embodied impacts. Such benchmarks are often derived with a bottom-up approach consisting of a statistical analysis of the building stock, which is usually modelled based on a limited set of representative buildings or archetypes. In this paper, a data-driven approach is applied based on building data from the Flemish Energy Performance of Buildings (EPB) database. In a recent study, the buildings from the EPB database were clustered based on geometric and energy-related parameters, and for each cluster representative buildings were selected. This resulted in 54 buildings representative of newly built residential buildings in Flanders. The building set distinguishes itself from other existing sets because it was automatically generated from a large building database. Up until now, the EPB building set has only been used to evaluate the financial feasibility of energy performance levels in Flanders. In this preliminary study, an LCA is performed to assess the life cycle environmental impacts of five sample cases in view of benchmarking. The sample includes two detached, two semi-detached, and one terraced house, all solid construction and in line with the Flemish EPB requirements of 2014. The results show that the environmental score of the buildings is comparable to benchmark values obtained based on the analysis of Belgian archetypes. Further, the building geometry and compactness are identified as key parameters, whereas the materialisation has a more limited influence on the environmental impact. Next research steps will focus on the modelling of more cases, including different construction types, energy performance levels, and potential impact mitigation strategies. The study concludes that the EPB buildings are promising to define environmental benchmarks for the Flemish dwelling stock.

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