Energy modelling of ETFE membranes in building applications

ETFE (ethylene tetrafluoroethylene) is a lightweight material increasingly used in building applications. It has gained popularity mainly due to its daylight transmittance and the potential for energy savings. When used as cladding ETFE sheets are usually assembled into cushions, which are inflated for structural reasons. ETFE cushions can provide thermal insulation with reduced initial costs and less structural supports as compared with a conventional glazed roof. Limited research regarding the modelling of ETFE in building applications and limited availability of information on material properties led to the present study. Designers are currently facing difficulties when carrying out energy optimisation studies as part of the design process. For example, since ETFE is not entirely opaque to longwave radiation, merely treating the material as a standard glass layer can lead to errors when evaluating its thermal performance. In order to enable building designers to assess the performance of these systems, maximising performance and managing risk, it is essential to gain knowledge and develop methods to model this novel material. This study takes into account the longwave transmission properties of the ETFE material and discusses the need for a methodology for estimating surface temperatures, heat losses, and solar gains. Guidelines for integration are needed to define its properties and to evaluate performance during the building design process.