Slotted lightweight steel sections for thermal improvement of building envelopes

Thin‐walled steel sections are used as substructures in multi‐shell constructions of metal facades to create space for thermal insulation. They transfer parallel and vertical loads acting on the outer cladding into the load‐bearing system. Thus, they penetrate the layer of thermal insulation and form a thermal bridge. The resulting thermal losses can be e.g. compensated by higher insulation thicknesses or the change of material selection, but both options usually come along with an increased demand of material and additional costs. By inserting slots in the webs of the steel sections the thermal bridge effect can be reduced. The use of one‐piece substructures enables a faster and thus more cost‐effective installation compared to classic two‐part substructures consisting of a bracket and mounting rail system. Although linear components initially exhibit a greater thermal bridge effect, due to the prolongation of the heat flow through slotted webs these can be thermally improved. However, the insertion of slots weakens the section, which requires the consideration of its load‐bearing behaviour. The improvement of thermal behaviour and the reduction of the load‐bearing capacity is investigated in ongoing research. First results show that both thermal and structural requirements of building practice can be achieved by the investigated slotted steel sections.