A cultural shift and new regulations would support the reuse of carbon-intensive materials
BUY LOCAL
Contractors are encouraged to source buildings materials nearby to cut embedded emissions
BEHOLD BEAUTY
Cultural perception of buildings should change to reduce level of steel, glass and concrete
KEY QUOTE
It’s easy if you have the materials. The great disadvantage is that the materials don’t exist in large scale
Triple paned windows offer better insulation than double-paned, which is why thousands of windows are being replaced. But the now-obsolete windows end up being discarded, like the single pane windows before them. They might end up at recycling plants, where glass and wood sometimes get sorted for reuse. But the windows themselves are gone. If you combine two double-paned windows you get a quadruple-paned window. It is bigger and the walls around it need to be designed in a new way. But by doubling up, an energy-saving window has been installed, any waste has been minimised and the production of new windows has been avoided. This process forms part of a quiet revolution happening inside the construction sector. A much-needed shift in a cautious sector with a huge CO2 footprint. One of the revolutionaries behind this activity is architect Anders Lendager, founder of the Lendager Group. Besides being an architectural firm, the company has also launched a range of businesses adapted to handle different types of waste. Lendager is not the first to come up with the idea of reusing construction waste, but he is the first to do it with success in Denmark and its neighbouring countries. Doubled double-paned glass windows and 1400 tons of upcycled concrete have been used at a row of terraced houses at the Upcycle Studio in Copenhagen. Lendanger has saved 32% in CO2 emissions on construction materials alone. “Those buildings are proof this is possible. I’d go as far as saying it’s easy if you have the materials. The great disadvantage is that the materials don’t exist in large scale”, Lendager says.
BUILDING BOOM BECKONS According to the United Nations Environment Programme (UNEP), the acquisition of construction materials makes up around 10% of total global CO2 emissions—other estimates reach as far as 15%. This amounts to roughly 3.2 gigatonnes of CO2—more than four times the emissions from all air traffic. 
The construction sector is getting back into gear after a tumultuous year affected by the Covid-19 pandemic. Many experts foresee a building boom in the coming decades, mainly driven by the growing urbanisation of Asia, South America and Africa. According to Michael Havbro Faber, a construction expert at Aalborg University, since 1990 cement production in China has increased by a factor of ten, by a factor of five in India and a factor of 50 in Vietnam. Some projections see a doubling of the global building mass within the next 40 years, adding a staggering 230 billion square metres of buildings—an area the size of New York City—every month. 
CEMENT AND STEEL Faber leads a number of international construction organisations including the Global Consensus on Sustainability in the Built Environment (GLOBE), which works to highlight how bad the sustainability of the construction sector is. “If something doesn’t happen very soon, the construction business alone could pull us all down with it,” says Faber. He quickly identifies two materials that really hurt the green transition: steel and cement—the main ingredient in concrete. Both are favourites with architects and engineers alike. A quick look at any modern city tells that tale. But both materials are also defined by the need for extreme heat in their production. Steel is melted at 1600°C and concrete is made at over 1500°C. The only practical way of getting to those extreme temperatures is to burn coal or gas, which is why both materials emit such large amounts of CO2. The steel sector emits 1.8 tonnes of CO2 per tonne of steel produced. Therefore, it is vital that both the production and reuse of these two construction materials is brought under control. Lendager is well aware that reusing old windows is not going to be enough to make construction sustainable. The use of construction materials also needs to be considered. Steel is already reused to a great extent, although the reclamation process is very energy-intensive. Meanwhile, concrete has been a more challenging proposition. Concrete is so solid that the only way to reuse it to date has been to crush it and use it as road filling. To get truly sustainable concrete, you would need to reuse the concrete for its original purpose. “Concrete’s massive CO2 footprint makes it a highly valuable material. You can’t just simply use it as road filling,” Lendager says. When Lendager realised there were no solutions to that problem, he sat down and attempted to solve it himself. This decision led to him establishing a sister company focused on upcycling materials that otherwise would be destined for less valuable uses like road surfacing. The company recently had its plan to use crushed concrete as an aggregate in the production of new concrete approved by authorities. 
KEEP IT UGLY The construction sector needs a fundamental overhaul in the same way the climate crisis is best solved with structural and systemic changes to the energy system. “The so-called mining of our trash for reuse of its resources is no doubt part of the way towards a sustainable building sector. But this part of circularity cannot stand alone,” says Thomas Osdoba from NetZeroCities, a think tank, and an advisor at EIT Climate-KIC, an EU-backed innovation platform. According to Osdoba, the challenge can be split into three main issues. Firstly, building development and land use need to be reconsidered in a whole new way. There needs to be less building activity and more refurbishment, says Osdoba. Meanwhile, any new buildings should be built lower, more compact, more durable and with locally produced materials. This way construction demands less steel and concrete and the lower concentration of both housing and commercial developments will make it easier for local authorities to be self-sufficient when it comes to energy and water. Secondly, the definition of building aesthetics needs to change so that beauty does not necessarily mean steel, concrete and glass. This would require a cultural shift to retain the facades of older buildings but to modernise them when it comes to energy use, thereby avoiding wasteful demolition. “There’s a trade-off between tearing down and preserving ugly duckling buildings or buildings that are maybe 70% as good as we’d like them to be. Those are issues we need to get our head around,” Osdoba says. Osdoba’s final issue is over the need to redesign the construction sector’s entire supply chain. “The supply chains required to build sustainably just aren’t there. They literally do not exist,” Osdoba explains. It will take time to build them; forests do not grow overnight. Part of the solution is to avoid importing wood from far away. Osdoba believes the majority of materials for a construction project need to be sourced from what he calls the construction project’s own “bioregion”. In reality, this means that in the EU, Scandinavian countries have to build with wood, while Southern Europe could use stone and brick, while the countries in between can use both. Builders should also utilise the reusable materials found in houses destined for demolition within in the bioregions.
FINANCING THE BUILD All these changes demand new building regulations and tariffs. But just as important, Osdoba points out, is a reformation of the way we finance construction. Typically financers have strict expectations towards both risk and earnings, which leaves very little room to try something new. In order to counteract this, Osdoba says local authorities should take on this risk. “I’m very critical of how local, regional, national and supranational governments in Europe and the United States have avoided taking responsibility for how the capital market has been created,” Osdoba says.
GREEN NEW DEAL Reform of finance capital could be a part of the European Green New Deal, where circularity makes a significant appearance. The European Commission is working on legislation that will make it mandatory for all construction projects to keep a detailed inventory, where all materials used in construction are accounted for to aid future reuse. There is also talk of mandating the easier dismantling of construction materials. So-called modular construction, which architects like Lendager have been supporting for decades, may also become a more popular option. Lendager also eagerly awaits new regulations and building codes, which will make the work easier. “The most sustainable square metre is the one you don’t build,” he says. •
TEXT Rasmus Thirup Beck & Søren Bjørn-Hansen PHOTO Bernardo Lorena Ponte