Wooden high-rises and hemp heritage homes

Until recently, biobased building materials like hemp were relatively untested. Now, Europe is starting to use them in major construction projects.

In France, Denmark, and the Netherlands, the first biobased high rises, school buildings, heritage homes, and sports centres are proving that plants offer practical alternatives to unsustainable concrete.

Biobased materials can do many things that conventional materials cannot: shorter supply chains and heritage renovations are just some areas where they can surpass steel and concrete. 

Here, we cover some of the most important projects in Europe’s first wave of modern biobased construction. 

A Dutch wooden high-rise

The construction sector is one of the most polluting industries on the planet thanks to its use of carbon-intensive cement and concrete. To replace these materials, plant-based substitutes will be key. 

Today, the strength of plant-based construction materials is no longer in doubt. For proof, look to Urban Woods Delft – a building project using wood to build low-carbon high rises in the Dutch city. 

When finished, Urban Woods Delft will become the tallest residential building in the country that does not have a concrete core. The tower block will reach ten stories when finished, although the method can allow buildings of up to fifteen storeys, according to the architectural firm behind the project, Arcadis. 

Instead, its load-bearing structure is made of cross-laminated timber. The material is made from recycled materials like pallets and reclaimed demolition wood, making it not just biobased but circular too. 

Timber is not the only biobased element at play. The block’s interior walls are made from flax and wood fibre. In fact, most elements in the building design have at least some biobased content, right down to the facades, which feature a biobased fire resistant composite known as Duplicor. 

The project is a major test case for the commercial viability of biobased construction. The buildings will eventually contain 102 mid-range rental apartments for the private market.

Urban Woods Delt is a radical move away from the mined materials that have defined urban environments for at least a century, offering a real-world blueprint for sustainable housing construction elsewhere.

A first for French hempcrete 

In 2021, France unveiled its first public building made of hempcrete: the Pierre Chevet sports hall. 

The building is located in the small town of Croissy-Beaubourg near Paris – an unassuming spot for the future of construction to be taking shape. The building itself looks modest too. There are no hints in its sleek, minimalist facade that any biobased elements have been used at all. 

For the most part, the biobased elements remain hidden inside. Within the walls are interlocking hempcrete blocks, assembled just like ordinary concrete blocks would be, into solid internal walls.

The hempcrete used in the sports centre was made by cement manufacturer Vicat, a French company founded in 1817. The hemp blocks were actually made from the hurd, or fibrous core, of the hemp plant – a part that is usually discarded, since there is low market demand for it. 

Using hempcrete can drastically lower the embodied carbon of the building. Embodied carbon is the most important concept in sustainable construction. It means all the carbon emissions needed to extract, process, manufacture, assemble, and maintain the actual materials that make it up. It is where most

Hemp plants are incredibly efficient at absorbing carbon dioxide from the atmosphere and locking it up in its cells, making it far less carbon-intensive than concrete.  

Over half of the global construction industry’s carbon emissions stems from cement, bricks, and metals – the material used in the buildings themselves rather than the energy needed to power them. 

 However, a small portion also comes from the fuel used to transport resources to the site. The hempcrete makes savings here too, thanks to a very short supply chain: the plants used in the blocks were all grown and processed within 300 miles of the site. 

A wood, straw, and seaweed school

A biobased school extension in Denmark offers a masterclass in sustainable construction, exploiting diverse biomaterials to achieve a durable yet sustainable structure. 

The rural school extension is a 250 square metre structure made of eelgrass, timber, and straw instead of concrete, brick, and steel. 

The roof of the extension is made entirely of timber, while the panel system is made of compressed straw. The ventilation system is made of eelgrass – a common seaweed. 

Henning Larsen Architects designed the structure and estimated the building will last 50 years. According to them, the biomaterials used to make the building reduced its carbon footprint to a 6 kilos of carbon per square metre per year across its life span. 

Biobased buildings like these are set to become more common in the country thanks to Denmark’s stringent new carbon laws. 

Denmark became the first country in the world in 2023 to place mandatory limits on carbon emissions for certain new buildings – limits that are about to get a lot tighter.

Between 2025 and 2029, Denmark is set to phase in gradually stricter embodied carbon limits. By 2029, emissions from all buildings over 150 metres squared  will be capped at an average of 7.5 kilos per square metre per year, with the exact figure dependent on building type.

These Danish embodied carbon laws are among the most advanced in the world. It will be incredibly hard to keep within such mandatory carbon limits without drawing on biobased or circular materials. 

Hemp in French heritage 

Buildings are Europe’s biggest single energy consumer, as well as emitter, of carbon dioxide. 

Most of this is embodied carbon – the steel, cement, and concrete used in actually building the sites. But some of it comes from operational carbon – emissions from heating or cooling buildings. 

Luckily, operational carbon has a relatively easy solution: insulation upgrades. With the right insulation, buildings can cut their energy requirements drastically. 

When it comes to heritage buildings, however, conservation priorities can clash with energy efficiency. In France, social housing provider Maisons et Cités are using hemp blocks to square the circle. 

Maisons et Cités manages 64, 000 homes in Haus-de-France, northern France. Many are quaint former miners’ houses. As relics of old industrial Europe, most have been listed as UNESCO World Heritage sites.

For over a decade, the housing provider has  searched for a way to insulate these historic buildings. Doing so would protect them from damaging damp and heat fluctuations. 

However, insulation upgrades can be disruptive. Maison et  Cités  knew it wanted materials and methods that provided energy efficiency without destroying the red-brick charm of its housing stock. 

After a long process of trial and error, Maisons et Cités decided hemp offered the best solution. This natural insulation offered high performance with minimal effects on the aesthetics or structural integrity of the houses. 

The hemp insulation blocks were recently installed into 50 former miners’ houses for real-world testing. The next step will be to create a local hemp sector, something that will involve training contractors on how to work with the material on-site.  The successes of the initiative could pave the way for more biomaterials demand from the heritage sector. 

Supply chain gaps hamper biobased mainstreaming

One of the biggest barriers to mainstreaming biobased construction are gaps in the biomaterials supply chain. Unreliable feedstock availability and limited processing capacity is  limiting the number of buildings that can go biobased. 

The Netherlands has been actively trying to solve the supply problem. There, the Frisian Hemp Fibre Deal is trying to bring together private and public sectors to create an entire regional supply chain for hemp building materials, from feedstock to building blocks.

Supply chain building is not just a technical and economic task – it will also be a test of institutional and political capabilities. Building a value chain large and sophisticated enough to support a scaled industry will demand close collaboration between farmers, builders, housing providers, and public authorities. 

If it does manage to unite and coordinate players across the construction supply chain, the Frisian Hemp Fibre Deal will offer a template for how state and private players can work together to achieve complex decarbonisation projects. 

Building biobased knowledge

Across Europe, the first wave of modern biobased building is underway. These pioneering projects are proving that renewable materials can stand up to the competitive demands of commercial construction, where value, strength, and durability are key benchmarks. 

However, shifting towards biobased at scale in construction will demand a steep learning curve. These early biobased sites will generate invaluable know-how, teaching architects and construction firms on how to work with new materials under time and budgetary pressure.

The biobased experience being gathered by European building companies today will equip them to meet an incoming surge of demand for sustainable building materials. 

Stringent new building laws are coming into force across the region to reduce the climate impact of our buildings. These laws could be the push needed to take biobased building materials from design concept to mainstream. 

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