MASS BALANCE: Design strategies for lightweight, thermally massive construction systems

Abstract

The design of lightweight, thermally massive construction systems offers the opportunity to tackle two of the main challenges currently facing the built environment: the need to reduce the use of concrete, responsible for 5-8% of global carbon emissions, and the mitigation of the impacts of extreme heat events, which are becoming increasingly recurrent worldwide. This work presents new strategies to design and evaluate integrated construction elements that simultaneously consider their structural and thermal performance. Specifically, focusing on concrete floor systems becomes critical from both perspectives given their outsized contribution to structural mass and impact on thermal comfort.

Methodologically, this thesis proposes the application of computational fluid dynamics (CFD) to study the dynamic thermal behavior of structurally optimized slabs. By simulating the ability of the thermal mass and ceiling’s geometric shape to flatten daily temperature fluctuations, the impact on occupants’ thermal comfort is evaluated. At the same time, the activation of these floor systems by, for example, embedding water pipes is analyzed as an additional opportunity of integrating functions and further improving the performance of these systems. The results obtained demonstrate the possibility of designing shaped slabs that, in addition to a 55% embodied energy reduction relative to conventional prismatic solutions, can still increase their passive thermal mass performance by 6.5% and their active cooling capacity by 14.5%. Moreover, the implementation of multi-optimization techniques allows for the exploration of Pareto-optimal designs that, at the expense of lowering the material savings achievements to 38%, can further improve their thermal behavior up to 9.5% (passive) and 28% (active).