If the construction sector is to become sustainable, urban mining is key. But how do we mine our buildings, if we don’t know what they’re made of in the first place? That’s where a materials passport comes in.
Just as a regular passport provides personal details of someone’s identity, a materials passport provides insight into the identity of a building. Typically in the form of digital data sets, these records of exactly what materials, products, and components go into a structure make it vastly easier at the end of the building’s life to recover everything of value, preventing these materials from being dumped or incinerated during demolition or renovation.
As Dutch architect Thomas Rau says: “waste is material without an identity”. It is a vision he has put into practice as one of the founders of Madaster, who operate a public, online library of materials linked to their location. This platform allows stakeholders along the construction chain to upload building information modeling (BIM) data on a building, and automatically generate a materials passport.
Materials passports can cover everything from the foundations of a building, to the front facade, window frames, inner walls, and right up to the ceiling and roof structure. They can also detail the materials used in public spaces and infrastructure such as roads and bridges.
Beyond identifying what components are being used, a materials passport also allows for a better idea of the value of a particular building. Just as there are precise valuations of the space and location, a breakdown of the materials means it is easier to calculate the specific value of a building’s material worth. And this can add up: for instance, a study for the Metropolitan Region of Amsterdam calculated that the 2.6 million tonnes of building materials released each year through renovation and demolition in Amsterdam have a value of €688 million.
The theory of materials passports is already being put into action: the project Buildings As Material Banks (BAMB), an EU-backed collaboration between 15 partners from 7 European countries, undertook a range of pilot projects, including a new office building in Essen, Germany, using materials passports to build to Cradle-to-Cradle principles.
Informing sustainable design
Of course, simply recording what ingredients make up a building does not guarantee that those materials can be reused. In addition to specifying the materials that go into a building, a materials passport can also provide insight into how sustainable, recyclable, healthy, and safe they are. This doesn’t just provide information to users at the demolition and renovation stage: it can also serve as a prompt at the design phase to ensure that buildings are using components that can be easily and safely reused, such as Cradle-to-Cradle Certified Products like Daas ClickBrick facades: self-gripping bricks which install with fasteners rather than chemical connections, which allow for easy disassembly and reuse. Another example is Shaw Ecoworx carpet tiles, which are free of harmful chemicals to allow for recycling back into the raw material stream. These tiles go one step further, each labeled with a phone number and website for reclamation instructions.
Merlijn Blok, Built Environment Consultant at Metabolic, says materials passports play a particularly valuable role at the design phase. “Material passports support architects in conceptualizing buildings as material banks from which valuable products can be harvested after the buildings become obsolete,” he says. “By designing for disassembly and archiving information on the materials we’re adding to our built environment, architects can play a crucial role in sustaining a waste-free, circular economy into the future.”
Existing buildings can get passports too
Ideally, a materials passport is created before a building is constructed. But they can also be developed for existing buildings, through techniques such as plan analysis, and digital 3D scanning. These analyses can help building owners to understand the quality of the materials already in use in their buildings, and the lifespans of specific materials, informing timely maintenance. They can also be applied on a larger scale than just individual buildings, for instance, estimating the metal content of buildings across Amsterdam. There are plenty of possibilities for this to be taken further down the track. BAMB Material Passport Best Practices guide envisions augmented reality platforms allowing auditors and surveyors to walk through buildings and view data drawn out of material passports superimposed on the components they are looking at.
Record the journey
Passports don’t just reveal who we are: they allow us to travel, recording where we’ve been, when we went, and how long we were there. Similarly, a materials passport can help identify the most useful future destination for a building’s materials through clearer traceability: how many times has a particular material been reused? In what way was it reused or recycled? Who is the current owner, and who owned it previously? Although paper versions of material passports exist, it is in this respect that digital passports have particular potential, especially in conjunction with emerging solutions such as blockchain, which can be defined as an immutable record of data typically managed by a cluster of computers not owned by any single entity.
Towards a circular economy for construction
By enabling practices that extend the lifetime of building materials, materials passports could fundamentally reshape the business models that underpin the construction sector, and economy at large. Rau sees material passports as facilitating the journey towards the components that make up a structure being loaned out to buildings as a service. “All that is physical in a closed system is a limited edition in essence, and, thus, it has a value,” he says. “We have limited materials and it is service, not ownership, that facilitates the way we use them in an unlimited way. If we really want to change the world, we must change business models.”