Analysis & Comparison of the Carbon Footprint of CLT Floor Systems

Details

Supervisors

Latteur, Pierre

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil des constructions, à finalité spécialisée

Abstract

The construction sector remains one of the largest contributors to global greenhouse gas emissions, and as operational energy demand declines, embodied carbon has become a decisive lever in early-stage structural design. Floor systems represent a substantial share of the material quantities and embodied carbon of multi-storey buildings, which explains the growing interest in Cross-Laminated Timber (CLT) as a low-carbon alternative to reinforced concrete. This environmental advantage cannot be assumed by default, however, as it depends strongly on span, loading, panel configuration and serviceability requirements. A comparative parametric methodology is developed to evaluate both systems under equivalent design conditions, covering a wide range of spans, load levels, panel thicknesses, material classes and structural configurations. For each solution, structural feasibility is assessed through ultimate and serviceability limit state verifications — bending, shear, deflection and vibration — complemented by fire and acoustic considerations. Embodied carbon is evaluated for the A1–A3 life-cycle stages and combined with material cost through a multi-criteria compromise score, allowing configurations to be ranked according to their balance between carbon footprint and cost. The results show that the structural feasibility of CLT floors is governed mainly by serviceability criteria — long-term deflection and, for longer spans, vibration — while strength and fire resistance rarely control the design. CLT offers a clear advantage in terms of fossil embodied carbon but is considerably more expensive in material cost; for the office cases studied, reinforced concrete therefore obtains the better balanced score when carbon and cost are weighted equally. Reinforced concrete also remains preferable where longer spans, higher stiffness or acoustic robustness govern the design. Overall, neither CLT nor reinforced concrete is universally superior. The most suitable floor system depends on the design context and on the relative priority given to structural performance, carbon footprint and cost.