Quantification and prediction of the thermal performance of cold-formed steel wall assemblies

Steel elements installed at or in the building envelope are susceptible to forming thermal bridges, where heat and energy are transferred from the building interior to the exterior. Thermal bridges have a negative impact on overall embodied energy in the structure, which can be compounded over the service life of a building. Furthermore, poor thermal performance also results in condensation and occupant discomfort. This work specifically examines the thermal behavior of cold-formed steel wall assemblies. These assemblies are typically comprised of studs and tracks, sheathed in gypsum and weather-proofing sheathing. Walls are repetitively framed. While the performance and efficacy of insulating materials and potential mitigation strategies is known, prior works have not examined the impact of specific detailing inherent to these wall systems. To determine the influence of these engineering decisions, a large parametric study of wall assemblies was conducted via three-dimensional steady-state thermal analysis. The parametric study included steel thickness, stud depth, stud spacing, and was conducted across ASHRAE 90.1 climate zones. The contribution of isolated details and the sensitivity of overall thermal performance to these details is presented herein. Comparisons to relevant design codes are presented and predictive methods for determining thermal performance of assemblies are proposed.

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