Experimental study on the thermal performance of ethylene-tetrafluoroethylene (ETFE) foil cushions

ETFE pneumatic foil constructions are used increasingly by designers and builders as an alternative to glass in state of the art building envelopes. Low weight, high transparency, mechanical resistance and self-cleaning properties of ETFE may contribute to the overall performance. However, reliable information on the thermal performance of ETFE cushions in building envelopes is scarce, limiting the performance prediction in energy simulations. The present study aims to investigate the thermal performance of air-inflated ETFE foil cushions and evaluates parameters of material properties and design which might affect the thermal transmittance. The paper reports on the experiments conducted to quantify the thermal performance using a climate chamber and full-size mock-ups. Based on available standards, tests were designed to compare the thermal performance of three different ETFE cushion designs, under changing climate conditions. The design variations, including frit prints and switchable shading mechanisms, were tested and compared at hot, temperate and cold weather scenarios. The test series provided detailed results on the thermal performance of ETFE cushions which may be of use for the comparison with the performance of other building components and materials, serve as input for energy simulations and provide a theoretical basis for future developments of novel building envelopes.