Performance of Anidolic Daylighting Systems in tropical climates – Parametric studies for identification of main influencing factors Friedrich Linhart a, * ,1 , Stephen K. Wittkopf b , Jean-Louis Scartezzini a,1 a Solar Energy and Building Physics Laboratory (LESO-PB), Swiss Federal Institute of Technology in Lausanne (EPFL), 1015 Lausanne, Switzerland b School of Design and Environment, Department of Architecture, National University of Singapore, 4 Architecture Drive, Singapore 117566, Singapore Received 29 July 2008; received in revised form 20 August 2009; accepted 14 January 2010 Available online 27 April 2010 Communicated by: Associate Editor Harvey Bryan Abstract Making daylight more available in buildings is highly desirable, not only for reasons of energy-efficiency, but also for improvement of occupants’ health and well-being. Core-daylighting, that is daylight provision in areas situated at considerable distances from fac ßades and windows, is currently one of the main challenges in sustainable building design. Anidolic Daylighting Systems (ADSs) are one very promising technology in the field of core-daylighting, but commercial solutions that are not only well-performing but also financially competitive are not yet widely available. This article presents results of parametric studies on Anidolic Integrated Ceilings (AICs), a spe- cial type of ADS, for identification of main influencing factors. The article describes a reliable method for simulating ADS and AIC performance under given sky conditions. Various simulation results for the example location Singapore are discussed in detail, it is con- cluded that the main influencing factors are coating material, system dimensions and external obstruction, and those influencing factors’ potential impacts are quantified. It is shown that AIC overall efficiencies can reach up to almost 50% in Singapore. The essentially new results presented in this article can be of great help to architects, engineers and scientists in the future, when it comes to precisely dimen- sioning ADS for various buildings and daylight conditions. Ó 2010 Elsevier Ltd. All rights reserved. Keywords: Daylight; Anidolic; Office lighting 1. Introduction Reducing the artificial lighting load is one important step towards sustainable and energy-efficient buildings. It can be supposed to have a major impact on the CO 2 -foot- print of buildings because the demand for artificial lighting usually peaks at times of high electricity demand (i.e. dur- ing peak load) when fossil fuel consuming power genera- tors are used to meet our societies’ electricity needs (Aries and Newsham, 2008). Artificial lighting load reduction is particularly important in office buildings, where up to 40% of the overall electricity consumption can be caused by electric lighting (Jenkins and Newborough, 2007; Li et al., 2006; Wah Tong To et al., 2002). Outdoor illumi- nances often exceed the required workplane illuminances inside office buildings by several orders of magnitude. If sufficient daylight flux can be made available in office spaces without disturbing the occupants (e.g. through dis- comfort glare), the artificial lighting load can be drastically reduced and large amounts of electricity can be saved (Li et al., 2006; Wah Tong To et al., 2002). Ideally, artificial lighting might be less needed, depending on the glazing’s optical properties, window orientation and time of day (Linhart and Scartezzini, 2007, 2009). Making daylight more available in buildings is not only highly desirable for reasons of energy efficiency, but also for improvement of occupants’ health and well-being (Veitch, 2006). Core-daylighting, that is daylight provision in areas sit- uated at considerable distances from fac ßades and windows, 0038-092X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.solener.2010.01.014 * Corresponding author. Tel.: +41 21 6934540; fax: +41 21 6932722. E-mail address: friedrich.linhart@epfl.ch (F. Linhart). 1 ISES member. www.elsevier.com/locate/solener Available online at www.sciencedirect.com Solar Energy 84 (2010) 1085–1094