Construction in a circular economy will require a shared vision of reduced waste.
Waste is a major problem for the construction industry worldwide. In the UK, the industry produces three times more waste than households – and only half is recycled. This is unsustainable even in the medium term. Lessons should be learned from the manufacturing sector because a considerable structural change in the entire built environment industry is urgently needed.
So said Arup chairman Gregory Hodkinson, addressing a conference on the Circular Economy held at London’s Building Centre on 21 September. More than 200 delegates heard presentations from the likes of Hodkinson and Bam Construct UK sustainability director Nitesh Magdani on how construction can adopt the basic principles of the circular economy and move away from the current waste-generating traditional linear economy.
BenBlossom TheCircularBuilding S 11
Source: Ben Blossom
Circular construction, delegates were told, abandons the current “take-make-dispose” model. Materials, products and components would ideally be used again and again and maintain their highest possible value. Disposal should be avoided or postponed, assets shared, resource use optimised.
Buildings would seem to be obvious beneficiaries from adopting circular economy principles and practice. Rapid developing technologies – such as structural insulated panel systems – and the growth of offsite construction make it possible to largely eliminate wet trades – above foundation and ground floor level at least. Deconstruction can replace demolition when a building reaches the end of its life, with components being reused rather than being simply recycled or going to waste.
To illustrate the principles of circular construction, a team from Arup, the Built Environment Trust, Bam and Italian building envelope specialists Frener & Reifer had erected a demonstration building outside the Building Centre, which stood there for just a few days (see box). A more realistic example, perhaps, is Swansea University’s recently opened “Active Classroom” (see box).
We had to do more than just work out how we would put it together – we also had to consider how we could take it apart.
Arup director Stuart Smith
Although not primarily intended to demonstrate circular construction, the classroom’s five year life expectancy required it to be designed for deconstruction. It made economic sense for the building to be reused wholly or in part as after only five years virtually all the main components would be in good condition and thus still have significant value.
Arup director Stuart Smith listed the principles the team took on board when designing the demonstration building in London.
“Lease materials and products wherever possible, rather than purchasing,” he said. “Maximise off-site manufacture. Avoid wet trades. Select materials that can be re-used, remanufactured or recycled at end of life. And make deconstruction easy by avoiding adhesives and using mechanical or push-fit connections.”
He added: “We had to do more than just work out how we would put it together – we also had to consider how we could take it apart.
“This involved a lot of collaboration with the supply chain.”
A circular economy challenges traditional ideas of ownership.
Arup associate Simon Anson
The key technologies may be mature, and any developments that promise dramatic reductions in resource depletion and disposal to landfill are to be welcomed. But there were other, more pragmatic considerations raised at the conference.
“This is about more than minimising waste and maximising recycling,” Hodkinson warned. “We need to develop a business case for circular building as well.”
But Bam Construct UK’s Magdani raised the question of how clients would react to proposals to re-use “second-hand” materials and components in their new build projects.
“How would the residual value of such materials be calculated?” he asked. “Would clients demand warranties?”
“A circular economy challenges traditional ideas of ownership,” added Arup associate Simon Anson. “We need legal innovation as well as innovations in materials and construction, to allow the easy movement of materials through a circular economy.”
Despite these caveats, the reaction of delegates was almost universally positive. One factor that all agreed on was that for circular construction to become an everyday option, the entire supply chain had to work together. And no one disagreed with one central message – circular construction requires a changed mind set for all parties, and all parties must share the vision.
Case study | Circular by nature
BenBlossom TheCircularBuilding S 5
Those who visited the Building Centre during the London Design Festival last autumn expecting to see a cylindrical building erected outside were set for a disappointment. The Circular Building they found there was a more mundane creation at first sight. Resolutely rectangular in plan, its circularity lay in its embodiment of key principles of the circular economy. Its design, its procurement and its construction differed markedly from the traditional, yet the end result was functional and effective.
Arup associate and lead architect Simon Anson says design began with a 3D building information modelling (BIM) model – “and the suppliers were involved from Day 1.
“A shared vision was the secret. But we did find there were more suppliers already engaged in the circular economy than we had first thought.”
Virtually all the components were either recycled/recyclable, remanufactured, or “leased” – which for this demonstration project meant “on loan from suppliers”.
RHS steel offcuts from a project in Luxembourg were used for the main structural frame. The team had hoped to procure recycled timber for the floor beams, but were unable to locate anything suitable within the time available.
Right now it’s packed away in four containers. There are opportunities to deploy it to other sites.
Arup associate Simon Anson
Structural cassette panels produced offsite using CNC technology made up the walls and roof. These are particularly “green”, formed as they are from Ecoboard, a board manufactured from fibrous agricultural waste using low formaldehyde resins.
Such is the accuracy of manufacturing that the panels could be assembled using an interference-fit fixing technique – high friction joints – developed from Arup’s 2014 Wikihouse, a simple prototype buiding designed using open source software.
Rainscreen cladding was Accoya, an acetylised modified softwood with the appearance and durability of tropical hardwood.
Clips, clamps and other mechanical fixings were used throughout to allow straightforward dismantling without damage to the components. These included all glazing, such as the Velux units in the roof. Adhesives were banned.
Interior panels also simply clipped into place. There were no wet trades involved. Arup also took the opportunity to further develop some of the alternative technologies first pioneered on the Wikihouse.
So the electrical system is low voltage, and, in conjunction with renewable energy technologies and the latest developments in battery storage the building could function off grid. The ventilation system used equipment manufactured from recycled plastic, cardboard, and re-manufactured drinks cans.
Anson reports that the Circular Building took two weeks to erect, but just seven days to dismantle. “Right now it’s packed away in four containers.
“There are opportunities to deploy it to other sites. Eventually the components will be returned to the suppliers – they are best placed to put them back into their product streams.”
Case study | Not your average demountable
south and west elevations
Located on Swansea University’s Bay campus, the full size “active classroom” which opened last October was originally planned to demonstrate a range of new low carbon building technologies. These had been developed by the university’s Sustainable Product Engineering Centre for Innovative Functional Industrial Coatings (SPECIFIC), as part of its long-term “buildings as power stations” project. The new building’s main function was to trial this concept on a full scale building and collect priceless data on the technologies’ performance in service.
“But we only have planning permission for five years, after which the building has to disappear to make room for other developments,” explains SPECIFIC project architect Jo Morgan.“So we had to design it for deconstruction. In the process it also became an example of circular construction.”
Deconstructability starts with the foundations. Steel screwpiles 2.5m long were chosen, not just for their minimally disruptive installation but also their ease of ultimate removal. In five years’ time, all being well, the used screwpiles will be back in the supply chain and ready for use on subsequent projects.
Sitting on the piles is a grid of eminently recyclable 254mm deep steel UBs. Above this level the new technology takes centre stage.
Floor, walls and roof are constructed of innovative interlocking AcerMetric steel framed structural panels. Faced in fire resistant magnesium oxide (MgO) boards, insulated with expanded polystyrene (EPS), the panels were manufactured offsite and erected in just two weeks by a small team from Matrix Structures.
Apart from speed of erection, advantages claimed for the AcerMetric panels and its patented 3D interlocking elements include low noise installation using only hand tools, and ease of deconstruction. Roof, floor and wall panels differ only in detail: roof beams are integrated into the roof panels, floor panels have an integrated base.
Rainscreen cladding comes from Tata Steel’s long established range of coated steel – hardly surprising since Tata is one of Swansea University’s strategic partners in SPECIFIC, along with industrial chemicals giant BASF and glass producer NSG Pilkington.
From a distance the only difference between individual elevations is colour. Much closer viewing is needed to spot the microperforations in the cladding to the southern elevation, nor is the 100mm plenum behind the cladding obvious.
It’s a real alternative to conventional temporary classrooms.
SPECIFIC project architect Jo Morgan
Together these form a transpired solar collector. Some 95% of the solar energy falling on the cladding is absorbed: the air behind the cladding is heated, rises, and is drawn off into the building’s heating system via small fans. Cool air flows in through the hot microperforations to replace it, and is heated in its turn.
Electricity is generated by an even newer technology. Thin film solar cells are bonded onto steel roof panels to create a Building Integrated Photovoltaic (BIPV) roof. Electricity from the 17kWp BIPV array is stored in two massive saltwater batteries – combined storage capacity is enough to power the classroom for at least two days.
Additional space heating comes from SPECIFIC-developed electrical resistive floor tiles powered from the battery storage. These have a fast response time, making them ideal for the classroom situation, Morgan says.
She adds: “Because this building is so easy to deconstruct and then rebuild elsewhere, this circular construction approach is ideal for schools. Build time can be as little as five weeks, so this can be done in the school holidays. It’s a real alternative to conventional temporary classrooms.”