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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 91
Edited by: B.H.V. Topping, L.F. Costa Neves and R.C. Barros
Paper 107

Thermal Improvement of Lightweight Façades containing Slotted Steel Girders

J. Varadi and E. Toth

Department of Building Constructions, Budapest University of Technology and Economics, Hungary

Full Bibliographic Reference for this paper
J. Varadi, E. Toth, "Thermal Improvement of Lightweight Façades containing Slotted Steel Girders", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 107, 2009. doi:10.4203/ccp.91.107
Keywords: lightweight, façade, building physics, thermovision, numerical simulation, thermal properties.

The subject of this paper is to adapt a lightweight façade system containing slotted steel girders from a building physics point of view (e.g. thermal properties) to the Hungarian standards and requirements. The most important advantage of the system, in terms of its thermal behaviour, comes from the load bearing element of the façade system. The web of the steel girders are slotted, which provides an advantageous heat conductivity behaviour, since the heat has to go around the slots, so the heat needs more time to go through the façade.

The façades with different claddings can be applied in two different ways: as a new additional floor for existing buildings, as infills or as a curtain wall for reconstruction or newly built reinforced concrete skeleton buildings.

Different levels of the façade are simulated. The questions are: what is the effect of the slots in the web at different web depth and wall thicknesses, of the wall thicknesses at the basic layers, and of the number of girders in one wall section. The other simulations show the effect of the additional claddings and the validation of simulations with the help of thermovision images of a structure previously constructed.

The heat flow will decrease because of the slots. The improvement was 70% on average for girders with 150 mm web depths and at wall thickness of 1 mm.

The Hungarian regulations prescribe that the required value U should be 0.45 W/m2K for façades. The heat transmittance for a façade containing only the basic layers (gypsum boards, girders and infill insulation) will be below this value for girders with 150 mm web depth and 1-1.2 mm wall thickness, and for all girders with 200 mm web depth, if a façade with one girder is calculated. If there is additional cladding on the façade, these values will decrease more.

As the number of girders increase in the façade, exterior additional insulation is needed to achieve the required value. For instance the presence of the second girder gives an additional 50% increase in heat flow. The additional layers cause a positive change in the heat flow. Compared to the required value, these results are 50% better.

At the validation of the simulations with thermovision photos the same results, Ti,min= 21.8 K occurred for both the computer simulation and the thermovision images for the interior side of a façade. So it can be said that the validation of the simulations are correct. As a conclusion it can be said that this lightweight façade system fits the Hungarian regulations and requirements.

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