The circular economy in construction has what you might call an image problem.

Most people assume it means recycling, but what it actually means, more often than not, is never letting a material become waste in the first place.

Ivana Kildsgaard, sustainability director at the Scandinavian practice Tengbom, told us about a discovery that reframed her work: office furniture thrown out while still under warranty.

It was all done and finished, in the eyes of a system with no mechanism for a second owner.

That’s one of the big problems in miniature, and it’s why the circular economy in construction matters more than any recycling target.

This post draws on Kildsgaard’s work at Tengbom and with the Hundragruppen platform (episode 12) to look at what circularity actually requires, from the data to the design decisions.

 

Why Linear Building is Running Out of Road

Circle Economy’s Circularity Gap Report puts the global circularity metric at 6.9%. That’s to say that more than 93% of materials entering the world economy are virgin.

The same report notes that resource use has tripled since 1970, and human-made materials now outweigh all living biomass on Earth.

That’s pretty crazy to think about, right?

And construction is central to this. Take, for example, how the UK Green Building Council reports that construction, demolition, and excavation generated 120 million tonnes of waste in a single year, so that’s roughly 59% of all UK waste.

On top of that, the quantity of reused materials in UK construction has actually decreased since 1998.

What does that tell us?

The industry got better at diverting waste from landfill and worse at keeping materials in use. And those are not the same achievement.

Scale is behind the urgency. Arup estimates that construction consumes around half of all raw materials extracted globally, and that the world adds new buildings equivalent to the size of Paris every week.

At that rate, the circular economy in construction is an urgent consideration.

Kildsgaard’s furniture example scales this down to something you can picture.

Through Hundragruppen, the interior-industry platform she chairs, her group found that in some large public framework agreements, only around 1% of products purchased were reused, so 99% were bought new.

Sweden has 10 million people. Consider how many office chairs that implies, then consider where the old ones went.

What a Circular Economy Demands of Our Buildings

The circular economy in construction isn’t one singular intervention, or a singular consideration in the building process.

It’s a hierarchy of considerations, and it has an order to follow.

UKGBC’s circular economy principles lay out the sequence:

• Reuse the existing asset first: The greenest building is nearly always the one already standing
• Recover materials and products on site, or from another site nearby
• Design for longevity, flexibility, and adaptability so the building can change use without being demolished
• Design for assembly and disassembly so components can come apart without being destroyed
• Share materials for onward reuse rather than sending them to a skip

In particular, that fourth point is where architecture makes or breaks circularity decades in advance.

The RIBA Journal sets out the same hierarchy, indicating that retaining an existing building is the most resource-efficient option, followed by refits and refurbishments, with recycling treated as the last resort rather than the goal.

UKGBC’s design for deconstruction guidance makes the mechanism super concrete:

Use reversible connections like screws and bolts rather than glue and chemical fixings.

Bolted steel can be unbolted. Glued assemblies can only be broken.

Design decisions made in an afternoon determine whether a building’s materials have a future, which is exactly the whole-life thinking behind embodied carbon vs operational carbon.

The Data Problem

Here’s one of the most powerful insights, and a significant reframe,  from Kildsgaard.

Asked what Hundragruppen identified as the industry’s core barriers, she named criteria, standardization, and digitalization … and then explained why that last one is the linchpin.

If material information isn’t digitized, she argues, you cannot work with the circular economy in construction at all.

That sounds fairly abstract, but when you try to reuse something, it’s advice that makes a whole lot of sense. 

To specify a salvaged beam or a reclaimed window, you need its dimensions, composition, condition, and provenance. Without that record, no engineer signs it off and no insurer covers it.

The answer emerging across Europe is the material passport, a digital record of what a building contains and how it comes apart.

Platforms like Madaster function as a registry for the built environment, documenting quality, origin, and disassemblability so that materials retain identity rather than becoming anonymous rubble.

The Dutch approach puts it well. A material passport gives building materials an identity, preventing them from vanishing into waste.

Kildsgaard’s research through Hundragruppen followed the same logic, by quantifying the economic, environmental, and material potential of reuse. Turning this into hard data means it can become a clear specification.

The Market Must Go On

A material passport is just about useless without somewhere to sell what it describes.

This is the least glamorous and most decisive part of the circular economy in construction. After all, someone has to dismantle, store, clean, test, and resell.

Brussels-based Rotor DC has spent a decade building exactly that, a cooperative that salvages doors, flooring, lighting, and hardware from large buildings, then develops the deconstruction techniques and remanufacturing processes to make them saleable again.

They’ve also mapped Belgium’s existing salvage trade into a public directory (Opalis, now covering Belgium, France, and the Netherlands) on the reasoning that a market you can’t see isn’t much of a market at all.

Kildsgaard has watched the same ecosystem emerge in Sweden. Companies are inventorying products already in circulation, refurbishers are restoring them, and logistics operators are moving them.

This is an entire industry, she says, built on what already exists.

But she’s candid about the friction involved:

• Refurbished often costs more than new, so someone must be willing to pay the premium
• Budgets need certainty that novel approaches can’t yet provide
• “We tried that twenty years ago” remains a common and stubborn response
• Tools are missing, so teams have the ambition to reuse but lack the means to price and specify it

Policy is beginning to help, though. A Nordic Council review of reuse policies in the Nordics notes that Sweden’s performance-based building regulations place responsibility on the builder to select suitable products, which gives reused components a route to compliance that prescriptive rules would block.

Regulation has an impact on what’s buildable, a theme that also runs through our look at green building code challenges.

Getting Circular Without Getting Stuck

Kildsgaard’s practical contribution is a tool:

Tengbom’s “Sustainable by Tengbom,” a three-part framework of a goal-setting wheel, a toolbox, and an integrated process.

Her core insight is that sustainability is too vague a word to design with. Her definition and her client’s rarely match, so the first workshop exists to convert ambition into project-specific targets before anyone draws anything.

She also warns against a trap worth naming: optimize for carbon alone and you end up in a silo, forgetting the human beings who need daylight, views, and contact with nature (the very concerns at the heart of our biophilic design guide).

For anyone starting out, the practical path through the circular economy in construction looks something like this:

• Set circular targets in the brief, before design begins: BRE’s guidance points to concrete numbers worth borrowing, including diversion above 95% and reused or recycled content above 25%
• Audit before you demolish, treating the existing building as a materials bank, as in our guide to renewable materials
• Specify reversible connections wherever the structure allows
• Document everything so the next generation inherits information, not a mystery
• Find your suppliers early, since salvage markets run on availability rather than catalogs

And in particular, retrofit deserves a mention as the purest circular move available.

Keeping a building standing and upgrading its performance is the circular economy in construction at its simplest, and it underpins both EnerPHit certification and the economics we examine in what a passive house retrofit costs.

Courage As Design Tool

Kildsgaard returns to one word more than any other:

Courage.

The courage to raise awkward questions, to challenge a brief, to suggest the unconventional solution, all because in her experience, the biggest obstacle hinges on perception.

That resonates well beyond circularity, driving everything from smart, sustainable cities to every genuine advance in how we build.

A building is a bank of materials someone spent energy, carbon, and craft to produce.

The circular economy in construction simply insists we stop pretending otherwise.

At Building Green, we talk to the people making this real, the researchers, architects, and platform-builders doing the unglamorous work of keeping materials in use.

Nothing was ever really waste, so now, it’s time to our instinct was to keep, rather than toss.