Light steel framing is extensively used due to its good thermal and structural behaviour. Heat loss reduction and thermal comfort have been the main driving forces defining the design of these frames. With this form of construction it is important that some insulation is placed inside or outside the steel frame to provide a thermal break and avoid condensation.
There are two major construction types:
1. Warm frame construction where all the insulation is outside the steel frame. One disadvantage of this technique is the loss of any possible insulation benefit by not utilising the space between the steel frame studs.
2. Hybrid construction, where insulation is included both inside or outside the steel structure and in between the steel components.
A vapour control layer should be installed on the warm side of the internal insulation layer.
The internal lining usually consists of two layers of plasterboard to provide 1 hour fire resistance to the loadbearing steel frame.
Insulation used on the cold side of the steel frame should be non-combustible, or have a class1 surface spread of flame where it faces a cavity
External loadbearing steel framed walls typically comprise:
• Internal lining of 12.5 mm thick, Type 5 fire resistant plasterboard clad with 12.5 mm thick Type 1 vapour check plasterboard
• Wall panels formed from channels (top and bottom) and C-section studs with diagonal cross bracing and lintels as required by the design
• Mineral wool friction fitted between the studs
• Insulation on the outside of the frame to prevent thermal bridging through the steel framework
• An external cladding – this can be anything from a rainscreen cladding system to a traditional brick outer skin
Knauf Insulation products designed for use between studs in light steel frame applications are dimensioned to suit standard steel studs at 600mm centres.