Temporal analysis of the material flows and embodied greenhouse gas emissions of a neighborhood building stock

Low-energy building standards shift environmental impacts from the operational to the embodied emissions, making material efficiency (ME) important for climate mitigation. To help quantify the mitigation potential of ME strategies, we developed a model that simulates the temporal material flows and greenhouse gas embodied emissions (GEEs) of the material use in the construction and renovation activities of a neighborhood by combining life-cycle assessment with dynamic material-flow analysis methods.

We applied our model on a “zero emission neighborhood” project, under development from 2019 to 2080 and found an average material use of 1,049 kg/m2, an in-use material stock of 43 metric tons/cap, and GEEs of 294 kgCO2e/m2. Although 52% of the total GEEs are caused by material use during initial construction, the remaining 48% are due to material replacements in a larger timeframe of 45 years.

Hence, it is urgent to act now and design for ME over the whole service life of buildings. GEEs occurring far into the future will, however, have a reduced intensity because of future technology improvements, which we found to have a mitigation potential of 20%. A combination of ME strategies at different points in time will best mitigate overall GEEs.

In the planning phase, encouraging thresholds on floor area per inhabitant can be set, materials with low GEEs must be chosen, and the buildings should be designed for ME and in a way that allows for re-use of elements. Over time, good maintenance of buildings will postpone the renovation needs and extend the building lifetime.