In 2023, 3,000 Brussels civil servants will start working in Kantoor 2023, a residential-work complex aiming to serve as an example for future public construction projects in the city. The complex is the result of a Competitive Procedure with Negotiation, launched by the Agency for Facility Operations from Procura+ Participant Government of Flanders, for the procurement of the design and construction of a new building for city staff.

The procurement has resulted in the renovation of the two towers of the World Trade Center (WTC) in Brussels, with construction of a new block annexed between the towers. In terms of circularity, the current buildings are being used to the maximum. 62% of the current building will be reused or recycled. The parts that are broken down are being given a new life – for instance, 30,000 tonnes of the broken concrete is going to be used as recycled granulates in the new concrete, and will be Cradle-to-cradle (C2C) certified. Up to 95% of the new materials will be C2C certified.

The Agency for Facility Operations wanted to use this tender to set an example for circular construction. “In the future circular criteria need to be a standard part of construction tenders, but that transition will take time”, notes Almut Fuhr, consultant at the Agency for Facility Operations. Flanders aims to have a fully circular economy by 2050. To achieve this, the Agency will need to take on a pioneering role and implement and promote circular thinking throughout its operations.

Circular thinking is not only based on recycling and certification. It is also conceived in a forward-looking manner. The buildings are being designed in a way to enable functions to be switched for residential or non-residential use. In the beginning the towers will be used alternately per story for office and residential functions. The facade, HVAC, lifts, fire-safety, etc. are being designed so that they can serve various scenarios of usage. The neutral structure will ensure that offices, homes and hotel rooms be furnished within the same basic structure. The building will therefore not only focus on today’s needs, but will also be adaptable to tomorrow’s needs.

In terms of sustainable design, the roofs of the building and the conservatory are equipped with solar panels to the maximum. Heat and cold will be extracted from the ground with a cold-heat storage system, which will cover more than 60% of the energy demand. An exchange of energy between the functions will further reduce energy consumption.

In terms of biodiversity and green spaces, the structures include 2,400m2 of rooftop gardens, 2,850m2 of ‘air purifying’ facades, green office floors with 400 trees and 1,000 local plants, a greenhouse with 1,000m2 of unpaved surface and 25 large trees.

Fuhr notes that the size of the project made it easier to convince the design team, as well as contractors and manufacturers to heed the circular criteria. “Circular construction is all about collaboration. All different actors in the construction value chain need each other. If you do it on your own, it will remain much more expensive to re-use old materials than to use new ones. Aside from that, circular construction requires more manpower and more complex logistic processes.”

A future where circular criteria are standardized in construction tenders does not depend only on the willingness of public buyers to include them in their procurements. Designers and suppliers need to be able to work with such criteria and that still requires a period of transition, emphasises Fuhr. “This does not mean that current building procedures do not integrate circular ideas. We invite teams to think about how to make their designs more circular. But in these traditional tender procedures the link between the designers and the contractors is missing, leading to price still being the decisive factor.” Yet Fuhr is optimistic about the future, noting that Kantoor 2023 is a good example of how in the long term circular construction projects will be more financially viable, as it offers more potential to adapt the buildings to the needs of the citizens.

More about the results of the project, the tender objectives, and the requirements/criteria relating to sustainability and circularity, can be found here.