Elaboration of a Sustainability Assessment Method for Neighbourhoods

In the past decade, the neighbourhood scale has gained importance in the field of sustainable construction. To support designers and building stakeholders in the design of sustainable buildings and neighbourhoods, several sustainability assessment tools have been developed. Among these tools, a distinction can be made between scoring tools and Life Cycle Assessment (LCA) tools. Scoring tools assign scores to a number of criteria covering a wide range of sustainability issues, such as energy use, material use, water use, user transport and comfort. LCA tools are based on a systematic study of the environmental impacts caused during the entire life span of the building or neighbourhood. Although LCA tools are preferred because of their transparency and scientific base, current tools are mostly limited to the assessment of individual buildings and only cover the environmental dimension of sustainability.

In this PhD research a sustainability assessment method for neighbourhoods is developed using an integrated life cycle approach. This integrated approach combines an assessment of the economic, environmental and social performance of neighbourhoods, together with an assessment of the neighbourhood qualities. The assessment method is based on an existing assessment method for buildings, SuFiQuaD (i.e. Sustainability, Financial and Quality evaluation of Dwelling types), which is extended to the neighbourhood scale level and refined to include additional evaluation aspects related to operational energy use, operational water use, neighbourhood land use, user transport and neighbourhood qualities.

To deal with the complexity of the neighbourhood, a hierarchic assessment structure in line with the principles of the “element method for cost control” and a subdivision in various scale levels, is implemented. The approach, which is translated in a modular spreadsheet tool, is applicable during the various design stages, from rough estimations in the master planning to detailed impact calculations in later design stages.

The assessment method is applied to analyse the impact of neighbourhood elements (i.e. neighbourhood infrastructure and open spaces) and to compare four neighbourhood models with various layouts and built densities. First, the analysis reveals that neighbourhood elements have a non-negligible contribution to the neighbourhood impact, especially in low built density neighbourhoods, where these contribute to about 20% and 30% of the environmental and financial impact of material use respectively. Second, the comparison between neighbourhoods built according to former building practice (before the 1970s energy crisis) and current building practice (year 2017) shows the high influence of the construction standards. The environmental and financial impact of the neighbourhoods in line with the current practice is about 60% and 30% lower respectively, which is mainly a consequence of the stricter energy performance requirements. Third, the comparison between the neighbourhood models reveals the high influence of the urban form and built density. When considering the current building practice, environmental and financial impact reductions up to 10% and 20% respectively are obtained for the neighbourhood model with the highest built density, compared to the model with the lowest built density. Appropriate urban planning and denser neighbourhood layouts are therefore recommended to reduce the impact of the built environment.

Finally, the assessment method is compared with a number of well-known scoring tools for neighbourhoods. The analysis of various sustainability measures reveals many discrepancies between the life cycle impact results and the scores awarded in scoring tools, confirming that the use of scoring tools is not a guarantee for a reduction of the environmental and financial impact of neighbourhoods. Based on this analysis, recommendations are formulated to better capture environmental and financial issues in scoring tools.