Shape optimization of chilled concrete ceilings – Reduced embodied carbon and enhanced operational performance

Abstract

The design of lightweight, thermally activated concrete floor systems offers the opportunity to simultaneously tackle two of the most urgent challenges currently faced by the built environment: reducing the use of concrete, responsible for 5–8% of global carbon emissions, and implementing energy-efficient cooling strategies to mitigate the consequences of extreme heat events. This paper introduces a novel chilled concrete ceiling technology integrated into the structural floor slab. This system reduces embodied carbon and enhances operational performance through rigorous structural-thermal shape optimization. As a radiant ceiling with embedded water pipes, the system's cooling capacity improves due to the extended exposed surface provided by the shaping. Additionally, condensation risk decreases as thermal comfort is reached through warmer surface temperatures.Two cooling-dominated climates and five slab geometries are analyzed using a multi-objective optimization approach, achieving Pareto optimal designs that reduce their embodied carbon by up to 52.5% while achieving 12–14% operational savings relative to conventional prismatic floors. The latter can be reduced by as much as 22–32% at the expense of lowering the embodied savings to 30%. Further, this work introduces a novel method for simulating shaped thermally activated surfaces in Building Energy Modeling (BEM) platforms. An equivalent flat slab model is proposed to transfer the complex 3-D heat transfer processes captured by numerical Conjugate Heat Transfer (CHT) methods into annual, climate-specific simulations. This solution offers a flexible and modular framework that allows architects and engineers to replicate the structural-thermal analysis conducted in this work for other locations and geometries of interest.