[PhD Defense] 🎓Dr. Guirec Ruellan at ULiège

On March 31, 2026, Guirec Ruellan successfully defended his PhD at ULiège: “Energy Renovation of the Walloon Residential Building Stock: Determinants and Integrated Approaches” 👉 https://hdl.handle.net/2268/337211

This work addresses a question that remains central to the energy transition: Why is large-scale residential renovation still not happening fast enough?

Guirec’s contribution is both methodologically rigorous and practically grounded. Rather than focusing only on buildings, the thesis integrates: • technical characteristics of the building stock • socio-economic profiles of occupants • behavioral and decision-making factors. This combination reveals something essential:

👉 Renovation is not only a technical challenge. 👉 It is a systemic and social process.

📊 Key insights from the research

• More than 17% of the housing stock combines low energy performance with low-income households • Around 11% shows low performance despite high-income occupants • Socio-economic conditions often outweigh purely technical factors in renovation decisions • Tools like infrared thermography are useful, but information alone does not trigger action

👉 The implication is clear: Effective renovation policies must be targeted, differentiated, and context-aware

🔬 The thesis combines: • large-scale statistical analysis • clustering of building–occupant archetypes • thermographic surveys • participatory fieldwork in real neighborhoods. This creates a rare bridge between data, field observation, and policy relevance.

🌍 Why this matters

Europe’s climate goals depend heavily on accelerating the renovation of existing buildings. But without understanding who renovates, why, and under which constraints, progress will remain slow. This work provides a framework to move from: 👉 generic policies → targeted interventions 👉 technical potential → real implementation

👏 Congratulations to Dr. Guirec Ruellan

It was a privilege to supervise this work and to see it develop into a coherent and impactful contribution to building science and policy.

🙏 Thanks as well to the jury and collaborators for their engagement and critical discussions. Griet Verbeeck, Sofie Pelsmakers, Stephane Monfils, Sigrid Reiter, Mario Cools and Shady Attia 阿提亚 沙帝.

💬 For researchers and policymakers: How do we better integrate technical, social, and economic dimensions in renovation strategies?

📚 Learn more about Dr. Ruellan's publications: https://orbi.uliege.be/ph-search?uid=u219698

Ruellan, G. (2026). Energy Renovation of the Walloon Residential Building Stock: Determinants and Integrated Approaches [Doctoral thesis, ULiège - Université de Liège]. ORBi-University of Liège. https://orbi.uliege.be/handle/2268/337211

Ruellan, G., Lalé, V., & Attia, S. (2026). Linking Building Conditions and Household Realities for Neighborhood-Scale Residential Energy Renovation. Sustainability, 18 (3), 1370. doi:10.3390/su18031370

Ruellan, G., Attia, S., & Haesbroeck, G. (15 May 2025). Clustering of archetypal building-inhabitant pairs to improve energy efficiency: The case of the Walloon region in Belgium. Energy and Buildings, 335, 115549. doi:10.1016/j.enbuild.2025.115549

Ruellan, G., Cools, M., & Attia, S. (19 February 2021). Analysis of the Determining Factors for the Renovation of the Walloon Residential Building Stock. Sustainability, 13 (4), 2221. doi:10.3390/su13042221

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