Comparative life cycle and energy performance analysis of a circular office building in a temperate climate

Abstract

This study evaluates the whole-life environmental and energy performance of cross-laminated timber (CLT) versus reinforced concrete in office buildings, using 't Centrum (Westerlo, Belgium), Belgium’s first certified circular CLT office building, as a real-world case study. Life cycle assessment (LCA) was conducted following ISO 14040/44 and EN 15978 (stages A1–A5, B4, B6, C3–C4; 50-year horizon), combined with dynamic energy simulation in DesignBuilder. Four construction material scenarios and four heating, ventilation, and air conditioning (HVAC) configurations were assessed. Net life cycle global warming potential (GWP) for the CLT reference scenario is 9.97 kg CO₂e/(m²·year), representing a 30% reduction compared to the best-performing concrete alternative (14.34 kg CO₂e/(m²·year)), reported using the EN 15804 + A2 − 1/ + 1 biogenic carbon convention with fossil and biogenic flows disaggregated separately. Although CLT’s lower thermal mass increased overheating risk, adding bio-based thermal inertia materials reduced thermal discomfort hours by up to 25% per EN 16798–1 adaptive comfort criteria, with negligible carbon impact (< 1%). Operational energy consumption was comparable across structural systems. HVAC equipment accounts for 68% of material-related emissions in CLT buildings due to repeated replacement cycles over the building lifespan. Sensitivity analysis (Morris method) identified the electricity mix and HVAC system type as dominant uncertainty sources. In high-performance Belgian buildings, embodied carbon, not operational energy, is the decisive lifecycle factor, and CLT combined with bioclimatic design and low-carbon HVAC systems represents a credible circular pathway toward carbon–neutral construction in temperate climates.

Keywords

Life cycle assessment / Embodied carbon / Cross-laminated timber / Circular building / Energy optimization / HVAC system / Thermal comfort

References

[1] United Nations Environment Programme. (2023). Building Materials and the Climate: Constructing a New Future. United Nations Environment Programme. Nairobi. Retrieved October 25, 2025, from https://wedocs.unep.org/20.500.11822/43293

[2] United Nations Environment Programme. (2025). Global Status Report for Buildings and Construction 2024/2025: Not just another brick in the wall - The solutions exist. Scaling them will build on progress and cut emissions fast. United Nations Environment Programme. Paris. https://doi.org/10.59117/20.500.11822/47214

[3] Commission européenne. (s.d.). Le pacte vert pour l’Europe. Retrieved October 15, 2025, from https://commission.europa.eu/strategy-and-policy/priorities-2019-2024/european-green-deal_fr

[4] SPW Énergie & Bâtiment Durable. (s.d.). Obligations – Performance énergétique des bâtiments (nouvelle construction). Energie. Wallonie. be. Retrieved November 25, 2025, from https://energie.wallonie.be/home/performance-energetuique-des-batiments/batiments-residentiels/nouvelle-construction/obligations.html

[5] Nordic Sustainable Construction. (2024). Danish political agreement tightens the limit values for new buildings and extends the impact. Retrieved April 22, 2025, from https://www.nordicsustainableconstruction.com/news/2024/june/tillaegsaftale-paa-engelsk

[6] Germanwatch, NewClimate Institute & Climate Action Network. (2025). Belgique – Climate Performance Ranking 2025. Climate Change Performance Index. https://ccpi.org/country/bel/

[7] Andersen JH, Rasmussen NL, Ryberg MW. Comparative life cycle assessment of cross laminated timber building and concrete building with special focus on biogenic carbon. Energy and Buildings, 2022, 254. ArticleID: 111604

[8] Dupas, N., & Hudert, M. M. (2024). Enabling the circular use of Cross-Laminated Timber by upcycling production waste. Research Portal Eindhoven University of Technology. https://research.tue.nl/en/publications/enabling-the-circular-use-of-cross-laminated-timber-by-upcycling-/

[9] Sun, Q., Huang, Q., Duan, Z., & Zhang, A. (2022). Recycling Potential Comparison of Mass Timber Constructions and Concrete Buildings : A Case Study in China. Sustainability, 14(10), Article 10. https://doi.org/10.3390/su14106174

[10] Duan Z, Huang Q, Sun Q, Zhang Q. Comparative life cycle assessment of a reinforced concrete residential building with equivalent cross laminated timber alternatives in China. Journal of Building Engineering, 2022, 62. ArticleID: 105357

[11] Himes, A., & Busby, G. (2020). Wood buildings as a climate solution. Developments in the Built Environment, 4, Article 100030. https://doi.org/10.1016/j.dibe.2020.100030

[12] Hoxha E, Passer A, Saade MRM, Trigaux D, Shuttleworth A, Pittau F, Allacker K, Habert G. Biogenic carbon in buildings: A critical overview of LCA methods. Buildings and Cities, 2020, 1(1): 504-524.

[13] Attia S, Gobin C. Climate Change Effects on Belgian Households : A Case Study of a Nearly Zero Energy Building. Energies, 2020, 13(20): 5357.

[14] Khavari AM, Pei S, Tabares-Velasco PC. Energy Consumption Analysis of Multistory Cross-Laminated Timber Residential Buildings : A Comparative Study. Journal of Architectural Engineering, 2016, 22(2): 04016002.

[15] Aquawal. (s.d.). Impacts actuels et attendus sur le cycle de l'eau en Belgique. Retrieved May 31, 2025, from https://www.aquawal.be/fr/le-changement-climatique-impacts-actuels-et-attendus-sur-le-cycle-de-l-eau-en-belgique.html?IDC=604

[16] Paul, J. (2014). Étude thermique dynamique d’une construction à ossature bois à inertie renforcée. [Mémoire de master, Université de Liège].

[17] Allan, K., & Phillips, A. R. (2021). Comparative Cradle-to-Grave Life Cycle Assessment of Low and Mid-Rise Mass Timber Buildings with Equivalent Structural Steel Alternatives. Sustainability, 13(6), Article 6. https://doi.org/10.3390/su13063401

[18] Artun, H., & Alemdağ, E.L. (2023). The Effect of Cross-Laminated Timber (CLT) Material on Building Heating-Cooling Loads in a Temperate Humid Climate Zone. Gazi University Journal of Science Part B: Art Humanities Design and Planning, 11(1), 47–60. https://www.academia.edu/111017774/The_Effect_of_Cross_Laminated_Timber_CLT_Material_on_Building_Heating_Cooling_Loads_in_a_Temperate_Humid_Climate_Zone

[19] de Paula Filho, J. H. M., D’Antimo, M., Charlier, M., & Vassart, O. (2024). Life-Cycle Assessment of an Office Building : Influence of the Structural Design on the Embodied Carbon Emissions. Modelling, 5(1), Article 1. https://doi.org/10.3390/modelling5010004

[20] Iuorio, O., Gigante, A., & De Masi, R. F. (2023). Life Cycle Analysis of Innovative Technologies : Cold Formed Steel System and Cross Laminated Timber. Energies, 16(2). https://doi.org/10.3390/en16020586

[21] Al-Obaidy, M., Courard, L., & Attia, S. (2022). A Parametric Approach to Optimizing Building Construction Systems and Carbon Footprint : A Case Study Inspired by Circularity Principles. Sustainability, 14(6), Article 6. https://doi.org/10.3390/su14063370

[22] Röck, M., Saade, M. R. M., Balouktsi, M., Rasmussen, F. N., Birgisdottir, H., Frischknecht, R., Habert, G., Lützkendorf, T., & Passer, A. (2019). Embodied GHG emissions of buildings – The hidden challenge for effective climate change mitigation. Applied Energy, 258, Article 114107. https://doi.org/10.1016/j.apenergy.2019.114107

[23] Bertini, A., Al-Obaidy, M., Dasse, M., Amaripadath, D., Gobbo, E., & Attia, S. (2025). Parametrization of variables affecting the whole life carbon performance of nearly zero energy residential building renovation. Building and Environment, 113013. https://doi.org/10.1016/j.buildenv.2025.113013

[24] Royal Institution of Chartered Surveyors. (2024). Whole life carbon assessment (WLCA) for the built environment (2ᵉ éd.). RICS. https://www.rics.org/profession-standards/rics-standards-and-guidance/sector-standards/construction-standards/whole-life-carbon-assessment

[25] Nakano, K., Karube, M., & Hattori, N. (2020). Environmental Impacts of Building Construction Using Cross-laminated Timber Panel Construction Method : A Case of the Research Building in Kyushu, Japan. Sustainability, 12(6), Article 6. https://doi.org/10.3390/su12062220

[26] Younis A, Dodoo A. Cross-laminated timber for building construction : A life-cycle-assessment overview. Journal of Building Engineering, 2022, 52. ArticleID: 104482

[27] Andersen, C. M. E., Rasmussen, F. N., Habert, G., & Birgisdóttir, H. (2021). Embodied GHG emissions of wooden buildings: challenges of biogenic carbon accounting in current LCA methods. Frontiers in Built Environment, 7, Article 729096. https://doi.org/10.3389/fbuil.2021.729096

[28] Pittau, F., Dotelli, G., Arrigoni, A., Habert, G., & Iannaccone, G. (2019). Massive timber building vs. Conventional masonry building. A comparative life cycle assessment of an Italian case study. IOP Conference Series: Earth and Environmental Science, 323(1), 012016. https://doi.org/10.1088/1755-1315/323/1/012016

[29] Pierobon, F., Huang, M., Simonen, K., & Ganguly, I. (2019). Environmental benefits of using hybrid CLT structure in midrise non-residential construction: an LCA based comparative case study in the U.S. Pacific Northwest. Journal of Building Engineering, 26, Article 100893. https://doi.org/10.1016/j.jobe.2019.100893

[30] Amaripadath D, Santamouris M, Attia S. Climate change induced heat stress impact on workplace productivity in a net zero-carbon timber building towards the end of the century. Building Simulation, 2024, 17(6): 893-906.

[31] Kang Y, Jo HH, Kim S. Enhancing indoor comfort and building energy efficiency with cross-laminated timber (CLT) in hygrothermal environments. Journal of Building Engineering, 2024, 84. ArticleID: 108582

[32] Shin B, Chang SJ, Wi S, Kim S. Estimation of energy demand and greenhouse gas emission reduction effect of cross-laminated timber (CLT) hybrid wall using life cycle assessment for urban residential planning. Renewable and Sustainable Energy Reviews, 2023, 185. ArticleID: 113604

[33] Dong, Y., Cui, X., Yin, X., Chen, Y., & Guo, H. (2019). Assessment of Energy Saving Potential by Replacing Conventional Materials by Cross Laminated Timber (CLT)- A Case Study of Office Buildings in China. Applied Sciences, 9(5), Article 5. https://doi.org/10.3390/app9050858

[34] Li, J., Andersen, L. V., & Hudert, M. M. (2023). The Potential Contribution of Modular Volumetric Timber Buildings to Circular Construction : A State-of-the-Art Review Based on Literature and 60 Case Studies. Sustainability, 15(23), Article 23. https://doi.org/10.3390/su152316203

[35] Pomponi F, Moncaster A. Circular economy for the built environment: A research framework. Journal of Cleaner Production, 2017, 143: 710-718.

[36] European Committee for Standardization (CEN). (2006a). Environmental management - Life cycle assessment - Principles and framework. (ISO 14040:2006). CEN, Brussels, Belgium. https://edu.nbn.be/data/r/platform/eduportal/detail?p40_id=193649&p40_language_code=en&p40_detail_id=35765&session=11442232200785

[37] INIES. (s.d.). Données environnementales et sanitaires des produits et équipements de la construction [Base de données]. https://www.base-inies.fr

[38] OneClick LCA Ltd. (2021). Embodied Carbon Benchmarks for European Buildings. Retrieved February 22, 2025, from https://143253260.fs1.hubspotusercontent-eu1.net/hubfs/143253260/Ebooks/Embodied-Carbon-Benchmarks-for-European-Buildings-10-June-2021-FINAL.pdf

[39] European Committee for Standardization (CEN). (2012). Sustainability of construction works - Assessment of environmental performance of buildings - Calculation method. (EN 15978:2012). CEN, Brussels, Belgium. https://edu.nbn.be/data/r/platform/eduportal/detail?p40_id=242541&p40_language_code=en&p40_detail_id=64768&session=130601289022

[40] European Committee for Standardization (CEN). (2019a). Sustainability of construction works - Environmental product declarations - Core rules for the product category of construction products. (EN 15804: 2012+A2: 2019). CEN, Brussels, Belgium.https://edu.nbn.be/data/r/platform/eduportal/detail?p40_id=221296&p40_language_code=en&p40_detail_id=91296&session=130601289022

[41] Service public de Wallonie. (s.d.b). Q-ZEN – Quasi Zéro Énergie. Retrieved March 27, 2025, from https://energie.wallonie.be/fr/q-zen.html?IDC=9842

[42] Kamp, C. (2020). Kamp C wint Europese Procura+ Award. Retrieved May 26, 2025, from https://www.kampc.be/nieuws/kamp-c-wint-europese-procura-award

[43] Kamp, C. (2018). Circulair bouwen: “Materialenpaspoort maakt hergebruik van materialen makkelijker”. Retrieved April 1, 2025, from https://rb.gy/5aiqey

[44] Al-Obaidy, M., Carens, H., Campain, C., Giannasi, E., Mori, M., van Vliet, M., & Attia, S. (2025). Expert system for building disassembly potential evaluation and inspection. Journal of Building Engineering, 103, Article 112148. https://doi.org/10.1016/j.jobe.2025.112148

[45] Kamp, C. (2022b). Calculus bouwt innovatief beheerplatform voor ’t Centrum. Retrieved April 23, 2025, from https://www.kampc.be/nieuws/calculus-bouwt-innovatief-beheerplatform-voor-t-centrum

[46] Claeys, L. (2022). Evaluation of energy performance and carbon emission of vacuum insulated glazing versus triple glazing in an office building in Belgium. [Mémoire de master, Université de Liège]. https://matheo.uliege.be/handle/2268.2/14600

[47] American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). (2002). Measurement of Energy, Demand, and Water Savings (Guideline 14–2002). ASHRAE, Atlanta, GA, USA. https://www.eeperformance.org/uploads/8/6/5/0/8650231/ashrae_guideline_14-2002_measurement_of_energy_and_demand_saving.pdf

[48] AIB. (2025, 30 mai). European residual mix 2024. Retrieved October 7, 2025, from https://www.aib-net.org/facts/european-residual-mix/2024

[49] ScienceDirect Topics. (s.d.). Morris Method – an overview. Retrieved May 19, 2025, from https://www.sciencedirect.com/topics/engineering/morris-method

[50] Brandner R, Flatscher G, Ringhofer A, Schickhofer G, Thiel A. Cross laminated timber (CLT): Overview and development. European Journal of Wood and Wood Products, 2016, 74(3): 331-351.

[51] Vandervaeren, C., Galle, W., Stephan, A., & De Temmerman, N. (2022). More than the sum of its parts: considering interdependencies in the life cycle material flow and environmental assessment of demountable buildings. Resources, Conservation and Recycling, 177, Article 106001. https://doi.org/10.1016/j.resconrec.2021.106001

[52] Attia, S. (2026). Database of demountable structural connections for circular building construction: Experimental dataset and design parameters (Version 2). Sustainable Building Design Lab, University of Liège. https://hdl.handle.net/2268/342758

[53] Pylsy P, Lylykangas K, Kurnitski J. Buildings’ energy efficiency measures effect on CO2 emissions in combined heating, cooling and electricity production. Renewable And Sustainable Energy Reviews, 2020, 134. ArticleID: 110299

[54] ’t Centrum. (s.d.). Kamp C. Retrieved February 18, 2025, from https://www.kampc.be/projecten/t-centrum

[55] Madaster. (s.d.). Update on EU taxonomy’s circular economy requirements. Retrieved April 2, 2026, from https://madaster.com/inspiration/update-on-eu-taxonomys-circular-economy-requirements/

[56] Dodd, N., Cordella, M., Traverso, M., & Donatello, S. (2017). Level(s) – A common EU framework of core sustainability indicators for office and residential buildings : Parts 1 and 2 : Introduction to Level(s) and how it works (Beta v1.0). JRC Publications Repository. https://doi.org/10.2760/827838

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