Useful daylight illuminances: A replacement for daylight factors

The UDI paradigm is designed to aid the interpretation of climate-based analyses of daylight illuminance levels that are founded on hourly meteorological data for a period of a full year, and is well-suited for teaching purposes.

Abstract

The Useful Daylight Illuminances (UDI) paper proved to be a significant factor in the decision of the CIBSE to support the formulation of climate-based measures of daylight to replace the 50 year old overcast sky paradigm (ie daylight factors). The CIBSE have offered a substantive direct contribution towards an EPSRC research proposal that will formulate the new guidelines for daylighting of non-domestic buildings. That proposal is currently under review (Mardaljevic is the PI). 
\nThe UDI paper also led to an invitation for Mardaljevic to join the British Standards Institute (BSI Panel for the revision of BS 8206-2 Lighting for Buildings - Code of Practice for Daylighting). The revision of BS 8206-2 will contain a Technical Annex on "Climate-Based Daylight Modelling" (authored by Mardaljevic) which was derived from the UDI paper. The BSI are also supporting the aforementioned EPSRC proposal.
\nAdditionally, the UDI scheme has been the focus of debates in the US (eg in "Emerging Daylight Metrics" at Lightair International 2007) where the daylight factor basis of LEED is recognised as a major shortcoming. 
\nThe UDI scheme has been included in the DAYSIM software produced by the National Research Council of Canada. 
\nThe UDI paper was written by Mardaljevic based on work by Nabil, an RA in the IESD, line-managed by Mardaljevic and previously, as a PhD student, under his supervision.