Fire resistance of cavity insulated light gauge steel framed walls

Light-gauge steel framed (LSF) wall systems are made of cold-formed steel studs and tracks and lined with gypsum plasterboards. They are mostly cavity insulated to provide acoustic and thermal performance. Cavity insulation delays the temperature rise across the wall as it restrains the heat transfer. This delays the ambient plasterboard surface temperature rise and thus improves the insulation failure time of LSF walls. However, LSF walls are also used as load bearing walls. Having cavity insulation causes the fire side temperatures to increase rapidly, resulting in a higher temperature gradient across the stud depth. This leads to higher thermal bowing deflection and crack openings on the fire side plasterboard and exposing studs to higher temperatures. These effects reduce the fire performance of load bearing walls. However, most designers consider that cavity insulation is beneficial for all LSF wall configurations. Thus experimental and numerical studies were conducted to investigate the effect of cavity insulation in both load bearing and non-load bearing walls. Experimental study was conducted on four full-scale wall panels with and without cavity insulation. Fire test results showed that cavity insulation delays heat transfer and is beneficial for non-load bearing walls. However, cavity insulation significantly reduced the fire resistance of load bearing walls. Numerical study was then conducted to obtain the structural adequacy failure times for varying levels of applied loads. This paper presents the results of these studies including the stud failure times and temperatures. The results showed that the use of cavity insulation significantly reduced the fire resistance levels of load bearing walls.