Contents lists available at ScienceDirect Journal of Building Engineering journal homepage: www.elsevier.com/locate/jobe Optimisation of daylight admission based on modifications of light shelf design parameters Rizki A. Mangkuto a, ⁎ , Fathurrahman Feradi b , Rialdi Eka Putra b , R. Triyogo Atmodipoero a , Federico Favero c a Laboratory of Building Physics and Acoustics, Engineering Physics Research Group, Faculty of Industrial Technology, Institut Teknologi Bandung, Jl. Ganesha 10, Labtek VI, Bandung 40132, Indonesia b Engineering Physics Program, Faculty of Industrial Technology, Institut Teknologi Bandung, Jl. Ganesha 10, Labtek VI, Bandung 40132, Indonesia c Lighting Laboratory, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Osquars Backe 5, 100 44 Stockholm, Sweden ARTICLE INFO Keywords: Daylight Light shelf Spatial daylight autonomy Annual sunlight exposure Optimisation Genetic algorithm ABSTRACT This study was conducted to optimise daylight admission as ambient lighting in an open-plan examination room of a dental hospital in Bandung, Indonesia. Parametric design was conducted for new light shelves, to be placed on the east and west façades of the building. Optimisation was performed using genetic algorithm, taking into account the external and internal widths, external tilt angles, and specularity of the light shelves, for two sce- narios: keeping and removing the existing overhangs on both façades. The optimisation objectives were to maximise the spatial daylight autonomy at the perimeter area (sDA 300/50%(p) ) and minimise the annual sunlight exposure (ASE 1000,250 ) on the occupied floor area of the examination room. Different optimised values were obtained for the east and west façades. In the first scenario, the resulting objective function yields an increase of 4.9% compared to existing condition, whereas the increase is 16.7% in the second scenario. Both metrics in the second scenario have satisfied the criterion. Uncertainty in the first scenario is found smaller than that in the second scenario, due to the removal of overhangs that bring more daylight in the latter. 1. Introduction In the context of building design, daylighting is an important component that needs to be considered seriously in the approach to achieve energy efficiency and sustainability (e.g. [1–3]). Particularly in healthcare facilities, admission of daylight in spaces where patients are present is expected to create a positive healing environment, by en- hancing health condition of the patients and reducing the recovery time (e.g. [4–6]). In workplaces, it has been long known that access to daylight and view are beneficial in creating healthy, comfort, and productive working environment. It has been shown that human gen- erally perceive daylight and view as highly valuable features in build- ings (e.g. [7,8]). However, there are many situations in which daylight cannot pe- netrate effectively in buildings, particularly in the deepest part [9,10]. In an open-plan building site, for instance, the central space normally has got the least amount of daylight, while increasing the window area would not be possible due the risk of increasing the heating/cooling load. In such situations, daylight transporting system is a plausible and promising solution. Various types of daylighting systems exist, but many are mostly applicable for relatively large spaces in which there is sufficient space for placing the system. One of the systems that require only relatively small space is light shelf, which is a device specifically designed to direct daylight to the deeper part of the room, while also functioning as a shading device in blocking (direct) sunlight. A light shelf generally comes in the shape of a horizontal or inclined baffle, typically lies below a clerestory window, and above the ‘normal’ or view window [11]. Light shelves design and performance assessments have been re- ported and discussed by many researchers (e.g. [12–18]). One of the most important parts in designing light shelves is determining the op- timum parameter, to ensure a maximum performance. Nonetheless, most of the previous studies evaluated the relevant values using fac- torial design or one at a time, in optimising the parameter. Alter- natively, the use of reference curve has been promoted by Kurtay and Esen [19], for various locations based on selected latitudes, hence also with some degrees of uncertainty. Meanwhile, the use of parametric modelling and optimisation through evolutionary computing has https://doi.org/10.1016/j.jobe.2018.03.007 Received 27 November 2017; Received in revised form 13 March 2018; Accepted 17 March 2018 ⁎ Corresponding author. E-mail address: armanto@tf.itb.ac.id (R.A. Mangkuto). Journal of Building Engineering 18 (2018) 195–209 Available online 24 March 2018 2352-7102/ © 2018 Elsevier Ltd. All rights reserved. T