Assessing material and embodied flows related to building services in office buildings — the case of Brussels, Belgium

An increasing number of cities and regions are promoting reuse as a key strategy in the transition towards a more circular economy in the construction sector. However, the reuse supply chains for building services are currently underdeveloped in most cities and regions. There is a need for a better understanding of the material flows at the city and regional levels. This study describes a bottom-up approach to quantify material flows related to building services as well as their embodied environmental and economic flows. It relies on the selection of a minimum of 1 new construction or renovation project representing material inflows and 1 demolition or renovation project representing material outflows. Actual products from bill of quantities and pre-demolition audits are mapped against a list of 234 archetypes, and archetypal inflows and outflows are extrapolated to the city or regional level. This model is applied to all office buildings in the Region of Brussels, Belgium. Results show that rectangular ductwork is responsible for almost 30% of annual inflows of building services, which amount to 32 km/year, 1,6 kt/year, require 96 thousand m³ of freshwater/year, 131 TJ of primary energy/year, emit 9,9 kt CO₂ eq/year, cost 3;4 MEUR/year to project developers, and whose installation in buildings represents 51 khours/year. In addition, results show that the outflows of black steel pipes, recessed luminaires and electrical cables exceed the inflows on an annual basis, suggesting that there is significant potential for covering needs through the reuse of those products.