Impact of gravity detailing on the thermal performance of cold-formed steel wall assemblies
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Date
2020-10-20
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Abstract
Considering building thermal performance in addition to structural performance is paramount to sustainable design. Structural systems bleed heat from interior to exterior through thermal bridges, structural elements that either span the building envelope or dramatically reduce the efficiency of insulating components. Materials that have high thermal conductivities are particularly susceptible to forming thermal bridges; steel has a relatively high thermal conductivity compared to other building materials and demands attention. In cold-formed steel buildings, repetitively framed studs act as thermal bridges. As typical interior insulation is placed in the wall cavity, between wall studs, the studs impact the effectiveness of the insulation layer. This work aims to characterize and quantify the impact of design choices on the thermal performance of exterior structural cold-formed steel walls. This is accomplished via three-dimensional finite element modeling. First the models are validated against existing experimental and computational efforts, then expanded to capture a suite of common detailing. Stud thickness, web depth, and spacing are the focus of this paper. A range of climate zones (corresponding to continuous insulation thickness and cavity insulation R-value) are also explored. The results suggest that web depth does not impact thermal performance while stud thickness and spacing do contribute to the total energy lost through the structural system. This paper formulates recommendations to designers regarding cross-section selection and exterior wall detailing.