Materials expert: Data is key to circular construction

More buildings are being designed to be disassembled at the end of their useful lives. For this to be possible, we need transparency about the materials used – which is precisely the reason for the development of the material passport, which was launched in January 2023. Read an interview with Martha Lewis, Head of Materials at Henning Larsen.

Few architects in Denmark were present at the birth of one of the leading building certifications. But Martha Lewis, Head of Materials at Henning Larsen, was. She was on board when, in 2008, the firm won the commission to design the German media company Der Spiegel’s new head office in the HafenCity district of Hamburg.

“It was a project with very high ambitions with regard to sustainability, and a new certification system was specifically developed for the HafenCity district. That system was, so to speak, the beta version of DGNB. The experience with certified projects in HafenCity led to adjustments to the system, which then became DGNB in 2010,” she explains. 

The project included evaluation criteria for hypoallergenicity and restrictions on unwanted substances, which at the time was new to Martha Lewis:

“It was extremely interesting. Do you design without ledges and windowsills where dust can gather? Do you choose materials that don’t create dust? For example, we avoided radiators in our designs as we did not want any elements where dust can collect,” she explains.

Another criterion for the HafenCity project was that the materials should be free of so-called halogens (for example chlorine, fluorine, bromine).

“This meant that we had to product-screen the building materials. We looked at the halogen content in, for example, breather membranes, cables, electrical outlets, plastic profiles and fire retardants,” she says, adding that she learned a lot from the German engineers who were well ahead of the game in terms of material screening.

Photo: Martha Lewis, architect and Head of Materials at Henning Larsen Architects

From certifications to quantum leap

Since then, building certifications such as DGNB, LEED, WELL and BREEAM have gone from strength to strength – not least in northern Europe. However, the transformation which is needed in the construction industry will not be achieved on the back of building certifications alone, says Martha Lewis.

“In certified construction, we do everything a little bit better than you would in a traditional construction project. And it adds value. However, we’re not yet taking the quantum leap which is needed in terms of the way we build, the materials we choose, or our approach to design. Much more is needed to address the climate, chemistry and resource crisis which we’re currently facing,” she says.    

Martha Lewis has pinpointed weaknesses in the current certification schemes in terms of material health, and which should be given greater focus.

In a study in the five Nordic countries from 2019, she looked at how the certification schemes screen for problematic substances compared to the hazardous substances that are actually used in the construction industry in the respective countries.     

“The conclusion is that our certification systems often let us down in this area. They do not screen effectively for problematic substances, and fail to stop hazardous substances from getting through the screening process. In fact, auditors looking at the screening are not even asked to screen for the substances that are widely used in the countries in question,” she says.

For example, DGNB does not screen for the carcinogenic substance formaldehyde, even though more than 9,000 tonnes of the substance were used in the Danish construction industry in 2017 alone. Or for a bisphenol-A polymer, of which more than 3,000 tonnes were used in the construction industry. Bisphenol-A is allergenic and toxic to aquatic life with long-lasting effects.

“We must find a way of stopping these substances from being used,” says Martha Lewis, adding that many certification schemes cannot keep up with the research.

Consequently, they will always fall short if they want to put a stop to all harmful substances being used in construction. The exception is the Swedish version of BREEAM:

“The scheme does not seek to list all the substances that are banned. Instead, it screens for the properties of the substances. It looks at the consequential effects we want to avoid. In other words, whether substances are carcinogenic, damage fertility or cause foetal malformations. Building materials containing substances with these effects shouldn’t be used in construction,” she says. The Nordic Swan Ecolabel takes the same approach and has the same requirement.

Buildings designed to be disassembled

Martha Lewis, however, finds that the construction industry is undergoing rapid development at the moment. For example, projects are emerging where buildings are designed to be disassembled and reused after the end of their useful lives. This trend will gain further traction in the coming years, predicts Martha Lewis:

“We’ve been working with ‘Design for Disassembly’ on a couple of projects, and more and more people are definitely taking an interest in it. And with the second part of the EU taxonomy for sustainable activities coming into force in 2023, this will increase momentum even further,” she says.

The taxonomy, which aims to support sustainable investments, introduces reporting and documentation requirements that must be met for investments to be called circular.

But new ways of building are needed for it to be possible for buildings and building materials to be subsequently dismantled. The new methods have the potential to benefit both the users of buildings and the climate:

“Often, it is not the building material itself that is the problem, but the products you use to assemble the materials or in combination with the materials. They can contain problematic substances, and also make it difficult to take everything apart again. By assembling building materials mechanically, we can dispense with the need to use hazardous substances, while also making the materials easier to recycle, so it’s a win-win,” she says.

As things stand at the moment, choosing ‘the right’ building material which benefits the environment, the climate and people is not always straightforward:

“You are soon faced with conflicting considerations. A building material might have a low climate footprint, but on the other hand contain problematic substances. In such cases, you have to weigh up your options,” she says.

Circular construction requires data

On paper, buildings that can be disassembled make it easier for the materials to be reused in other projects. But there are challenges, acknowledges Martha Lewis:

“I think that the logistics and accountability are the main issues. Building materials cannot simply be removed from one building and reused in another. The materials will probably need to be stored somewhere before being used again. And who is responsible for the materials and who owns them during that phase? These are just some of the questions that need to be answered,” says Martha Lewis.

She adds that some companies are already working proactively to address these challenges. For example, by carrying out the necessary environmental screenings of building materials that are being cleaned and prepared for the next construction project. At the same time, there is the question of warranties and how long recycled building materials can be expected to last:

“Here, researchers at DTU are engaged in a promising project aimed at developing ways of conducting so-called non-destructive tests of building materials. Essentially, they are gathering information on the strength of recycled building materials,” says Martha Lewis. And such data will be crucial for the transition to more circular construction:

“This is data that increases the value of building materials in the circular economy. Information about the building materials is entered in material passports, so we know, for example, how many times an acoustic panel has been painted – and with what. The information from the material passports is transferred to a building passport that keeps track of any new materials that come into the building, and what happens to the materials which are already there,” she explains, adding that the material manufacturers have an important role to play in this respect.

“It’s very valuable that a company like Troldtekt has EPDs for most of their products. In fact, it’s crucial, because in the building industry we need to know more about the climate impact from the production of building materials, and the EPDs provide this information,” says Martha Lewis.

Launch of new material passport
On 17 January 2023 at the Circular Build Forum, Martha Lewis and Anna-Mette Monnelly, an architect and Sustainability Director of NREP, presented the Danish construction industry’s new material passport, also known as the Sustainable Build passport.

The companies and trade associations behind the material passport are: the Danish Association of Construction Clients (DACC), Danske Byggecentre (DB), Henning Larsen, Lendager Group, Molio, NCC, NREP, Søren Jensen, Swedish SundaHus and Troldtekt. Grundejernes Investeringsfond, Boligfonden Kuben and Danske Byggecentre have supported the project financially since 2019.

The material passport declares important information about construction products – for example, have chemicals or other ingredients been used in production that may be of relevance when assessing whether a product can form part of a circular economy in new buildings.

Together with a full life-cycle assessment for construction (Building LCA), the material passport is intended to enable the industry to create actual climate accounts for projects. Several material passports in combination can form the cornerstones of a building passport. The purpose of the building passport is to provide information about the building as a whole over time.


Henning Larsen

  • Founded in 1959 by the architect Henning Larsen.
  • Henning Larsen is part of the Ramboll Group.
  • The firm has offices in Denmark, Norway, Germany, the USA and Hong Kong.