The Construction Solution Has Been Here All Along: Renewable Materials

• The construction sector is responsible for almost 40% of global carbon emissions.
• Renewable materials can help improve the industry’s eco-friendliness, as the production of traditional materials depends on finite resources.
• Luckily, plenty of alternative ideas for renewable materials and efficient recycling management are now available.

“Let’s focus on gray energy,” says architect and sustainability expert Werner Sobek. Gray energy is the term used to describe the primary energy required to construct a building. And when it comes to saving energy, it’s much more effective to use recyclable building materials during construction than to save energy downstream when managing the building later.

That’s why an increasing number of architects rely on renewable materials, including Sobek for a clinic in Eisenberg and Kaden+Lager architects for Skaio, Germany’s tallest wooden skyscraper.

Skaio is just 34 meters (111 feet) high. Floor-to-ceiling windows break through the light-gray cladding like honeycombs in a beehive. It won’t be long before a taller German wooden building is constructed.

But it’s not Skaio’s height that earned the building and Berlin-based architecture office the German Sustainability Award for Architecture in 2021. The building is a pioneering statement for greater sustainability in the construction sector. Not only has it been made mostly of wood—a renewable raw material increasingly described by the media as a solution for climate-positive construction—no glue was used to build it. According to Kaden+Lager, all components can be disassembled and used again. It’s a model of what can happen when combining needs-based planning, urban densification, and climate-friendly construction.

Challenging the Demolition Culture

Awarding a project like Skaio signifies the German Sustainable Building Council’s (DGNB) commitment to combat throwaway culture. This year’s Pritzker Prize, the world’s most prestigious award for architects, also reflects the trend to recognize architectural firms that prioritize resource conservation. The 2021 Pritzker Laureates, French architects Lacaton & Vassal, prefer to add to buildings rather than demolish them.

These winners represent an important paradigm shift in thinking for the industry. According to the latest United Nations report, the buildings and construction sector is responsible for 38% of global carbon emissions and is not moving toward the Paris Agreement’s goal of keeping average global warming below 2 degrees Celsius quickly enough. As the global population continues to grow, raw materials such as sand and gravel—which are essential for the production of concrete—are becoming scarce and expensive. There is increasing political, economic, and ecological pressure for alternative building materials in the construction industry.

For German civil engineer, architect, and co-initiator of the DGNB Sobek, this industry shift is a welcome change. He was aware of the scarcity of resources back in the 1990s. Today, he has an empire of offices that spans from New York to Dubai to Buenos Aires. His portfolio ranges from facade planning and sustainability consulting for the ADNOC Tower in Abu Dhabi, United Arab Emirates, to the development of an energy concept for a clinic in Eisenberg in eastern Germany.

“We use a variety of different building materials, all of which are fully recyclable,” he told DEKRA Solutions. “The question of how to connect all these different materials is a very important one. It’s a matter of whether it can be ensured that all joins are also reversible or whether composite materials are created that can no longer be recycled by type.”

Sobek’s private home in Stuttgart, Germany, explains this best. Sobek calls his private home R128, which sounds a bit like a Star Wars droid and evokes images of an amazing smart home with all kinds of intelligently networked gadgets.

In fact, the name is just a slightly hipper abbreviation for his address, Römerstraße 128. This modestly sized house is entirely glazed and is situated on a slope, surrounded by nature. The interior is so minimalist you would assume it’s uninhabited. Sobek’s home is a manifesto for his thoughts: It uses as little energy as possible and consists of recyclable and reusable materials, including copper plates, glass, and steel frameworks that were previously part of other buildings. “My childhood dream was to live in a soap bubble on a green field,” Sobek adds. “Today, it’s a cubic soap bubble.”

Giulia Peretti, team manager building physics and sustainability at Werner Sobek Green Technologies, emphasizes the importance of measures that compensate for damage caused in the past—approaches such as reusing and recycling materials that have already been installed. The principle behind the concept is to regard the built environment as a space in which building materials are stored before being reused and recycled as part of the circular economy.

A Paradigm Shift in Construction 

One example of this ideal is  NEST, a modular research building on the campus of the Swiss Federal Laboratories for Materials Science and Technology (EMPA) near Zurich. Sobek is responsible for NEST’s Urban Mining and Recycling Module (UMAR), together with Dirk. E. Hebel, professor of sustainable building at the Karlsruhe Institute of Technology (KIT), and Felix Heisel. The copper sheeting around the glazing was once a church steeple roof, and the cladding was repurposed from a local savings bank.

Like Sobek, Hebel is one of the architects advancing this paradigm shift. For years, he has conducted research into alternative solutions with his students at the KIT Department of Architecture in southwestern Germany. He designed the Mehr.Wert.Pavillon for the German Federal Garden Show in 2019. Like NEST in Switzerland, this construction features recycled materials. The treelike structure’s steel comes largely from a coal-fired power plant that was dismantled further north.

Hebel explains that the structure uses no adhesives, foams, or paints, as it would otherwise not be possible to sort and recycle even supposedly ecological building materials. “From now on, we have to design and build so that rather than putting materials in landfills or throwing them away after the building is demolished, we can generate added value from them,” he says.

Although Hebel admits that the demand for buildings is still higher than the number of materials that could flow back into the material cycle, the use of regenerative organic materials that are produced, grown, and cultivated using sunlight could close this resource gap. In recent years, the construction industry has experimented with alternative building materials such as hemp, bamboo, and fungi. Such experimental projects include Hebel’s MycoTree, which was created for the Seoul Biennale of Architecture and Urbanism 2017, and the compostable Hy-Fi tower, which uses mycelia-based bricks and was designed by the American architect David Benjamin for the Museum of Modern Art in New York.

However, a building does not automatically become sustainable through prudent choice of materials alone. Hebel explains that architects have to ask how the materials will be connected, how repair-friendly and durable the building will be, and how to supply it with electricity and heating. The option of deconstructing a building to continue on its journey through the circular economy must also be taken into account from the very start of the planning process.

An Ecological Building Materials Passport

Hebel sees much potential in digitalization for managing materials information. “We need a cadastre for materials and a passport for every material,” he says, suggesting that such a register should provide a record of the composition, production, and mechanical properties of each material, as well as how much of the material is used in each building and how it has been incorporated. “We would then know where our valuable materials are and how to put them back into circulation.”

Current digitalization tools such as Autodesk Insight building-efficiency analysis software assist builders on the path toward more sustainable construction. And the new circular-economy service ReCapture by Swedish architecture firm White Arkitekter scans existing buildings to identify recyclable materials for conversion.

Sobek once warned against sacrificing style in the name of saving resources: Doing so would not make people excited and inspired by sustainable design, which wouldn’t be of service to the circular economy. “Architecture must be beautiful,” he says. “Because we can only love and care for beautiful things.”