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Retrofitting office buildings: Enhancing daylighting performance with switchable ETFE double-skin façades

Flor, J.; Sun, Y.; Beccarelli, P.; Wu, Y.; Chilton, J.


J. Flor

Professor of Building Physics

J. Chilton


This paper addresses the natural daylighting qualities of spaces enclosed by ETFE
multi-layer foil constructions with switchable features. The study focuses on the effects the
adaptive shading mechanism has on the internal space in terms of useful daylight illuminance and natural lighting qualities. The overall aim of the study was to gain more knowledge of the daylighting effects of ETFE cushions in façade systems. Moreover, to understand the daylighting benefits switchable ETFE cushions could generate when employed in a double-skin façade as part of energy retrofitting measures to reduce the energy consumption of buildings. For this purpose, a virtual office space enclosed with an ETFE double-skin façade was evaluated using dynamic daylighting metrics. The simulation study was based on ray-tracing methods, using Radiance software for calculating illuminance levels across a test grid within the office space. To account for the light scattering and angle-dependent optical behaviour of double-curved ETFE cushions, bidirectional-scattering-distribution-function (BSDF) was employed based on experimental measurements of spectral transmittance. The simulation scenarios included different window-to-wall ratios, ranging from a small window size of 30% to an almost fully glazed façade of 90%. The simulation was based on annual weather data with hourly values to produce a comprehensive picture of the daily and seasonal daylighting performance in different climates. Results of the simulations were expressed with dynamic daylight metrics in terms of useful daylight illuminance (UDI). Compared to a standard glazed façade, the results showed that a double-skin façade with switchable ETFE cushions could significantly improve daylighting conditions for office work tasks. The annual percentage of hours UDI was achieved expanded significantly in most of the analysed scenarios when a switchable ETFE double-skin façade was applied. Generally, it was observed that the light was more evenly distributed throughout the room. Using BSDF data for weather-based daylighting simulations might suggest new ways of analysing the daylighting performance of adaptive ETFE façades more comprehensively.


Flor, J., Sun, Y., Beccarelli, P., Wu, Y., & Chilton, J. (2021). Retrofitting office buildings: Enhancing daylighting performance with switchable ETFE double-skin façades. .

Conference Name 10th edition of the conference on Textile Composites and Inflatable Structures (Structural Membranes 2021)
Conference Location Online
Start Date Sep 13, 2021
End Date Sep 15, 2021
Acceptance Date May 31, 2021
Online Publication Date Nov 19, 2021
Publication Date Sep 14, 2021
Deposit Date Jan 21, 2022
Publicly Available Date Jan 21, 2022
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