[COST Action HELEN] Holistic design of taller timber buildings

The Future of Timber Buildings Will Not Be Decided by Timber

Most discussions about timber buildings focus on one question.

Can we build taller?

After four years in COST Action HELEN (CA20139), I believe we have been asking the wrong question. The real challenge is not height. The real challenge is transition. The transition from linear construction to circular construction. The transition from designing buildings for demolition to designing them for adaptation, repair, disassembly, and multiple lifecycles. The transition from optimizing individual disciplines to embracing truly holistic design. This is exactly what COST Action HELEN set out to achieve.

Over four years, more than 400 researchers from over 40 countries worked together across structural engineering, architecture, fire safety, durability, life cycle assessment, circular economy, digitalization, and sustainability to rethink how taller timber buildings should be designed. The result is one of the most comprehensive references published on the subject:

📖 Holistic Design of Taller Timber Buildings. I am lucky that our research team contributed three chapters addressing some of the most critical challenges facing the future of mass timber construction.

♻️ Disassembly and Reuse in Tall Timber Buildings: We demonstrate how Design for Disassembly, reversible structural connections, modular systems, and digital technologies can transform buildings into material banks rather than future demolition waste. Circularity begins at the design stage, not at the demolition site.

Cabrero, J. M., Ottenhaus, L.-M., Palma, P., & Attia, S. (2025). Disassembly and Reuse in Tall Timber Buildings: Advancing Circular Construction Practices. In <em>Springer Tracts in Civil Engineering</em> (pp. 341-349). Springer Nature Switzerland. doi:10.1007/978-3-032-02098-7_27 https://orbi.uliege.be/handle/2268/336287

🌲 How Long Can Timber Buildings Last? Current life cycle assessments often assume a service life of around 50 years. Our international survey of more than 120 experts suggests a very different future. Well-designed and properly maintained tall timber buildings can realistically exceed 150 years, fundamentally changing how we should evaluate sustainability and embodied carbon.

Attia, S., Verdier, T., & Van Acker, J. (2025). How Long Can Timber Buildings Last? Strategies for Service Life and Sustainability. In Springer Tracts in Civil Engineering (pp. 205). Springer Nature Switzerland. doi:10.1007/978-3-032-02098-7_16 https://orbi.uliege.be/handle/2268/336288

🌍 Lifecycle Impact Assessment: Learning from HAUT: Using the award-winning HAUT building in Amsterdam as a benchmark, we explore how embodied carbon, biogenic carbon storage, service life, hybrid structural systems, and end-of-life scenarios interact across the building lifecycle. Sustainable design requires optimizing the whole system rather than focusing on a single material.

Attia, S. (2025). Lifecycle Impact Assessment for Tall Timber Building: Learning from HAUT. In Springer Tracts in Civil Engineering</em> (pp. 177-185). Springer Nature Switzerland. doi:10.1007/978-3-032-02098-7_14 https://orbi.uliege.be/handle/2268/336290

Together, these chapters share one common message. The future of timber construction is not about replacing concrete with wood. It is about rethinking how we design buildings throughout their entire lifecycle. Designing for longevity. Designing for adaptability. Designing for circularity. Designing for the low-carbon transition.

This interdisciplinary perspective is the lasting contribution of COST Action HELEN and demonstrates why international research networks remain essential for accelerating innovation in the built environment.

My sincere congratulations to Gerhard Fink, Robert Jockwer, José Manuel Cabrero, all Working Group leaders, the Management Committee, Core Group, and the hundreds of researchers whose expertise made this remarkable scientific achievement possible. It was a privilege to contribute to this collaborative effort.

This publication reflects the collective effort of an exceptional international community. My sincere thanks to the editors Gerhard Fink, Robert Jockwer, and José Manuel Cabrero; the Working Group leaders Mislav Stepinac (WG1), František Wald (WG2), Francesca Fragiacomo (WG3), and Thomas Tannert (WG4); my chapter coauthors José Manuel Cabrero, Lisa-Mareike Ottenhaus, Pedro Palma, Tomasso Verdier, and Joris Van Acker; the Management Committee, Core Group, Grant Holder InnoRenew CoE, and the more than 400 researchers from over 40 countries whose collaborations, Short-Term Scientific Missions, Training Schools, workshops, and scientific exchanges made COST Action HELEN such a remarkable success. It has been a privilege to contribute to this interdisciplinary network advancing the transition toward safer, more sustainable, and more circular timber buildings.

📚 Open Access Book: https://lnkd.in/ehVHk5a5

📚 Learn more about the COST Action HELEN (CA20139) https://www.cost.eu/actions/CA20139/

📚 Learn more about our research https://www.sbd.uliege.be/

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