Urban infrastructure: Challenges for resource efficiency in the building stock

Sustainable development has typically been framed in relation to the impacts of new buildings without adequately considering the road and utility infrastructures. In addition, the pattern of investment and building work in most industrialized countries is changing from new build to alterations to the existing housing stock. Therefore, any discussion on sustainable development needs to include both the existing building stock and the urban infrastructure (roads and utilities) to support them. The focus is on the demand for raw materials in future housing and infrastructure construction, with the premise that the parameter 'consumption of raw materials' represents a diverse group of factors detrimental to the environment. First, findings from empirical investigations on the material stock of housing and infrastructure networks in building stock are presented and indicate a strong correlation between material consumption and building density. The lower the building density in a selected area, the greater the share of material stock absorbed by infrastructure. Second, a material flow model is used to estimate future demands for raw materials in the development of stock, using the example of the building stock in Germany. These results indicate that in certain scenarios the material flows for neighbourhood roads and supply infrastructure can be much greater than material flows for buildings, underlining the importance that infrastructure should be accorded in the sustainable development of building stock. The issues of urban infrastructure need to be included in both future building and urban assessment tools. The influence on the demand for material from transport and utility networks can only succeed when combined with a long-term and clear-sighted urban policy to resist a further expansion of residential areas. Furthermore, insights gained from material flow modelling can help in the efficient deployment, recycling and disposal of mineral raw materials form existing urban developments, thereby benefiting the environment.