The Importance of Stud Flanges Size and Shape on the Thermal Performance of Lightweight Steel Framed Walls

Abstract

Energy production still relies considerably on fossil fuels, and the building sector is a major player in the energy consumption market, mainly for space heating and cooling. Thermal bridges (TBs) in buildings are very relevant for the energy efficiency of buildings and may have an impact on heating energy needs of up to 30%. Given the high thermal conductivity of steel, the relevance of TBs in lightweight steel framed (LSF) components could be even greater. No research was found in the literature for evaluating how important the size and shape of steel studs are on the thermal performance of LSF building elements, which is the main objective of this work. This assessment is performed for the internal partitions and exterior façade of load-bearing LSF walls. The accuracy of the numerical model used in the simulations was verified and validated by comparison experimental measurements. Three reference steel studs were considered, six stud flange lengths and four steel thicknesses were evaluated, and five flange indentation sizes and four indent filling materials were assessed, corresponding to a total of 246 modelled LSF walls. It was concluded that the -value decreases when the flange length and the steel studs’ thickness increases, being that these variations are more significant for bigger flange sizes and for thicker steel studs. Additionally, it was found that a small indentation size (2.5 or 5 mm) is enough to provide a significant -value increase and that it is preferable not to use any flange indentation filling material rather than using a poor performance one (recycled rubber).

Thermal Performance of Double-Pane Lightweight Steel Framed Walls with and without a Reflective Foil

“…Since it is a bi-dimensional FEM numerical simulation due to the existence of only vertical steel studs (Figure 3a), only a 2D representative part of the double-pane LSF wall cross-section (400 mm width) was modelled, as previously illustrated in Figure 1. Nevertheless, in a previous research work [19] a similar 2D THERM model were compared with a 3D ANSYS model and, as expected, the thermal resistance difference between both models was very small, i.e., only 0.002 m 2 K/W. Therefore, in this work it was decided not to present a similar redundant comparison.…”

“…Notice that aluminium reflective foil thickness is very reduced (around 0.1 mm) and, therefore, its thermal conductive resistance was neglected. The emissivity of this aluminium reflective foil is 0.05 [23], the cold-formed galvanized steel is 0.23 [19], while for the remaining materials it is 0.90 [21].…”

“…Currently, there are several strategies to mitigate thermal bridges in LSF buildings' components, such as thermal break strips [12][13][14], slotted steel studs [12,15,16] and continuous external thermal insulation composite system (ETICS) [17,18]. Notice that even slight modifications in the steel frame, such as in the stud flanges size and shape, may have a significative influence on LSF elements [19].…”

A Critical Review on Optimization of Cold-Formed Steel Members for Better Structural and Thermal Performances

“…The thermal bridges formed by the accelerated use of steel have motivated many researchers to put efforts into researching in this field, analyzing thermal performance [150,162], and its improvement [163][164][165] or mitigating thermal bridges [48,166], the importance of flanking thermal losses [17], the importance of the size and shape of steel studs on the thermal performance [1], numerical simulations of CFS framed walls [146] and CFS buildings [153], development of analytical methods [156,158] and in situ measurement methods [161,167] to estimate thermal transmittance, comparisons between different methods [156,166], thermal insulation [18,157,168,169], the interaction of thermal and sound insulation [19], and thermal performance and energy efficiency [170][171][172]. Table 2 summarizes the important research works performed over the last two decades on the thermal performance of CFS structures.…”

“…Climate change is one of the most critical challenges that the world is facing today. The building sector plays an important role in the energy consumption and emissions released from the buildings [1,2]. Normally, a building uses energy throughout its life cycle, including direct energy used for construction, operation, rehabilitation, and demolition and indirect energy consumed to produce material used in its construction and installations [3].…”