Mitigation potentials for environmental impacts of construction material flows

Building energy consumption is an important contributor to global greenhouse emissions. Therefore, energy-efficient retrofitting and new construction is on the political agenda in most countries. It can be expected that... [ view full abstract ]

Building energy consumption is an important contributor to global greenhouse emissions. Therefore, energy-efficient retrofitting and new construction is on the political agenda in most countries. It can be expected that these efforts lead to reduced greenhouse gas emissions due to declining building energy demand. However, increased energetic retrofitting also leads to higher overall material turnover and increased insulation material flow.

We developed a bottom-up GIS-based building stock model to determine material flow of the Swiss building stock. The model uses a stochastic approach to determine element and building service life and therefore accounts for the dynamics due to material dwelling time. By means of prospective scenario analysis we determine future environmental impact of construction material flow. As population growth is expected to decline in Switzerland, the building stock changes from a growth state to a maintenance state where refurbishment is responsible for the majority of material flows. Moreover, the age composition of the Swiss building stock leads to a pronounced building renewal cycle within the next 20 to 30 years. For these reasons total environmental impact, caused by construction material flows, practically does not reduce in the next 40 to 50 years.

Another consequence of this development is that material output will increase significantly. Our model predicts comparable material input and output flows from 2040 onward. Since similar material fractions (mineral, insulation, etc.) occur, we identified important potentials for closing material loops. We use the geo-spatial and dynamic building stock model to quantify material re-cycling potentials. Hence, we can quantify the environmental benefits of different recycling options. For instance, we could show that re-cycling of insulation material has an important reduction potential. Assuming an ideal re-cycling of insulation material would yield in ca. 25% lower greenhouse gas emissions in 2055, compared to the base scenario.

The presentation gives an overview of the bottom-up dynamic MFA model and the relevance of construction material flows for the environmental impact of buildings. Furthermore, we highlight the environmental opportunities of closing construction material loops.