Assessing the Environmental Performance of Hybrid Timber-Concrete Systems in High-Rise Building

The construction industry has traditionally relied on reinforced concrete as the primary structural material in high-rise buildings, valued for its strength, durability, and fire resistance. However, its high environmental impact—mainly due to cement production, which contributes approximately 8% of global CO₂ emissions—has raised concerns about its sustainability. As global efforts to reduce carbon emissions intensify, alternative construction approaches are gaining traction. Among them, hybrid timber–concrete systems offer a promising solution by combining the carbon-storing benefits of timber with the structural advantages of concrete. This study evaluates the environmental performance of hybrid timber–concrete systems in a 40- storey, 120-meter high-rise tower by comparing five structural typologies that vary in the number of Cross- Laminated Timber (CLT) floor slabs. The reference typology consists of a fully concrete frame with a cast-in-place concrete core, BubbleDeck slabs, and brick walls. The four alternative designs retain the concrete core while progressively replacing concrete slabs with CLT and using CLT for the walls. Structural modelling is conducted using Karamba 3D, while embodied greenhouse gas emissions (EGHGE) are quantified based on Global Warming Potential (GWP) indicators from the ÖKOBAUDAT database and EN 15804+A2 standards. Acoustic and fire performance are also evaluated, ensuring compliance with Belgian fire regulations and NBN EN ISO 16283 standards. The results show that total emissions decrease from 11.3 million to 7.45 million kgCO₂e as CLT use increases—a reduction of over 34%. The study confirms the potential of hybrid systems to reduce embodied carbon while maintaining performance and regulatory compliance.