A CONSCIOUS TOMORROW: Biobased materials are gaining ground

There is a clear and growing integration of biobased materials in the Belgian construction practice. This is evident from a recent survey conducted by Ghent University as part of the Interreg project CASCO Carbon Sink Construction. The aim of this project is to develop an ecosystem for scaling up the use of local and natural building materials in the border region between Flanders and the Netherlands.

The aim of the survey was to give researchers an initial insight into the use of biobased insulation and building materials in the Belgian and Dutch construction practice. Interestingly, the survey, which took place between December 2024 and January 2025, referred back to a survey conducted in 2020. The latter took place as part of the TETRA project ‘To bio or not to bio’, a collaboration between Odisee University College, Ghent University and Buildwise, the Belgian innovation centre for the construction sector. Five years later, a similar group of respondents was asked whether and to what extent practices had changed over the past five years.

Wood fibre, wood wool, cellulose, lime hemp and straw

“By far the largest share of respondents were architects, followed by contractors and manufacturers/distributors”, explains Ruben Van den Bossche, author of the study and Assistant PhD researcher at the Building Physics Research Group (Department of Architecture and Urban Planning, Faculty of Engineering and Architecture, Ghent University, Belgium). “At the same time, there was a balanced distribution in terms of the country where the respondents are mainly based. 48% of respondents work in Belgium and 44% in the Netherlands.”

First and foremost, the survey shows how a number of biobased materials stand out from the crowd. It became very clear that materials such as wood fibre, wood wool, cellulose, lime hemp and straw have become common choices for insulation, with wood fibre leading the way. Looking to the future, there appeared to be a particular demand for pressure-resistant biobased materials such as glass foam granulate, shells and cork. Great importance is also attached to the technical product properties and environmental impact when freely choosing insulation materials.

“Focussing on which materials are used ‘often’, one notices a number of clear shifts”, we hear. "Where mineral wool, PUR/PIR and EPS were still the top three in 2020, their place is taken by wood fibre, wood wool and cellulose in 2025. What's more, wood fibre and wood wool are overtaking cellulose, the pioneering biobased material. The top five biobased materials are rounded off by lime hemp and straw, with straw in particular making strong gains (from 8% to 20%). Wood fibre and wood wool are frequently used by more than 50% and 40% of respondents respectively, which is also an increase compared to the results in 2020. This trend is generally noticeable: almost all biobased materials will be used more frequently by a larger proportion of respondents in 2025.

“Looking at the responses from architects and contractors, we see similar overall trends. Wood fibre and wood wool are the most widely used, with more than 95% and 85% of respondents applying them. Here too, we see that cellulose is used relatively less, by 85% of architects and 56% of contractors.”

Shift in construction methods

Another conclusion of the study is that biobased structural and finishing materials are widely established. This refers to wood-based panels, traditional timber frames and gypsum fibre boards. Biobased materials are most commonly used in traditional timber frame walls, as internal insulation or in pitched roofs. In addition, 89% of the construction professionals surveyed indicated that vapour-permeable construction was already being used, which is a significant shift in construction methods.

"53% of respondents indicate they often build completely vapour-permeable, 36% do so sometimes. I was somewhat surprised that only 11% indicate they never do this or are unfamiliar with the concept. In practice, there are also misconceptions about the concept of vapour-permeable construction. The use of timber frame construction without a vapour barrier but with OSB is by definition not vapour-permeable, but vapour-resistant."

“I also find it interesting that the survey shows that wood-based panel materials in particular are well established. Timber frame construction with solid beams remains the leader in terms of structure, followed by engineered wood (LVL, glulam, I-joists, etc.) and CLT. Gypsum fibre boards are the most frequently used finishing materials, followed by clay and lime.”

Challenges for biobased construction

On the other side of the spectrum, one conclusion is that biobased materials still face a number of challenges.

“Somewhat unsurprisingly, the price and the wait-and-see attitude of customers are the main stumbling blocks, because unfamiliarity often breeds caution”, concludes Ruben Van den Bossche. “It is therefore positive that construction professionals are also actively providing information about the possibilities of biobased materials, even if the customer does not explicitly ask for it. Other recurring concerns are the technical product properties and behaviour in contact with moisture. One conclusion is certainly that the availability and quality of documentation is crucial for the confidence of both the customer and the construction professional when it comes to unknown biobased materials.”

"There may still be a number of challenges, but it is important to remember that more than 90% of respondents indicate they are noticing an increasing use of biobased materials. There is also a clear demand for information and documentation on these materials for further implementation in practice. This is also being investigated in the CASCO project, with the aim of expanding and strengthening the chains of biobased materials in the broader construction sector."

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