Dynamic Daylight Performance Metrics for Sustainable Building Design

Abstract

The objective of this document is to promote the use of dynamic daylight performance measures for sustainable building design. The paper initially explores the shortcomings of conventional, static daylight performance metrics which concentrate on individual sky conditions, such as the common daylight factor. It then provides a review of previously suggested dynamic daylight performance metrics, discussing the capability of these metrics to lead to superior daylighting designs and their accessibility to nonsimulation experts. Several example offices are examined to demonstrate the benefit of basing design decisions on dynamic performance metrics as opposed to the daylight factor.

Annual Evaluation of Daylight Discomfort Glare: State of the Art and Description of a New Simplified Approach

“…Besides, the evaluation of daylighting in buildings has moved towards the so-called climate based daylighting modelling (CBDM) (Reinhart, Mardaljevic and Rogers, 2006;Mardaljevic, 2008), which is aimed at providing results representative of a long-term analysis (generally one year). An annual DGP analysis is far time consuming, as it requires an high dynamic range (HDR) image to be generated for each time-step (typically an hour) considered during the course of a year.…”

“…They are based on the annual workplane illuminance, which gives several advantages in terms of computation time. Two metrics estimate the percentage of occupied time for which a potential glare condition, corresponding to global illuminance over a threshold value, occurs in a point (DAmax (Reinhart, Mardaljevic and Rogers, 2006) and UDIexceeded (Nabil and Mardaljevic, 2005)), while a third metric (Annual Sunlight Exposure -ASE) considers the percentage of space with a direct illuminance from the sun over a threshold value (1000 lux) for more than a certain amount of time (250 hours) over the year (IES Daylight Metrics Committee, 2012).…”

Daylight Performance of a Translucent Textile Membrane Roof with Thermal Insulation

“…In 1989, the Daylight Autonomy (DA) parameter was proposed by the "Association Suisse des Electriciens" and further developed by Reinhart from 2001 to 2004 [34]. It was the first dynamic approach for daylighting indoor evaluation.…”

“…The Useful Daylight Illuminances (UDI), proposed by Mardaljevic and Nabil in 2005, is also a dynamic daylight performance measure that is based on work plane illuminances [34]. It also represents the percentage of hours during a period when the natural indoor illuminance values lie in certain borders.…”

“…Namely below 100 lx, between 100-2000 and above 2000 lx (UDI<100, UDI100-2000 and UDI>2000). As its name suggests, it aims to determine when daylight levels are 'useful' for the occupant, that is, neither too dark (<100 lx) nor too bright (>2000 lx) [34]. The upper threshold is meant to detect times when an oversupply of daylight might lead to visual and/or thermal discomfort [34].…”