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Energy and Buildings 38 (2006) 824–835

Findings from a survey on the current use of daylight simulations in building design
Christoph Reinhart *, Annegret Fitz
Institute for Research in Construction, National Research Council Canada, Ottawa, Canada K1A 0R6

Abstract This paper presents findings from a web-based survey on the current use of daylight simulations in building design. The survey was administered from December 2nd 2003 to January 19th 2004. One hundred and eighty five individuals from 27 countries completed the survey. The majority of respondents worked in Canada (20%), the United States (20%), and Germany (12%). Most participants were recruited through building simulation mailing lists. Their self-reported professions ranged from energy consultants and engineers (38%) to architects and lighting designers (31%) as well as researchers (23%). They worked predominantly on large and small offices and schools. Ninety one percent of respondents included daylighting aspects in their building design. Those who did not consider daylighting blamed lack of information and unwillingness of clients to pay for this extra service. Among those participants who were considering daylighting 79% used computer simulations. This strong sample bias towards computer simulations reflects that many participants had been recruited through building simulation mailing lists. Participants named tools’ complexity and insufficient program documentation as weaknesses of existing programs. Selftraining was the most common training method for daylight simulation tools. Tool usage was significantly higher during design development than during schematic design. Most survey participants used daylighting software for parameter studies and presented the results to their clients as a basis for design decisions. While daylight factor and interior illuminances were the most commonly calculated simulation outputs, shading type and control were the most common design aspects influenced by a daylighting analysis. The use of scale model measurements had rapidly fallen compared to a 1994 survey, whereas, trust in the reliability of daylighting tools has risen. While participants named a total of 42 different daylight simulation programs that they routinely used, over 50% of program selections were for tools that use the RADIANCE simulation engine, revealing the program’s predominance within the daylight simulation community. Crown Copyright # 2006 Published by Elsevier B.V. All rights reserved.
Keywords: Daylight simulations; RADIANCE; Online survey

1. Introduction In a rapidly changing world, design professionals rely more than ever on solid performance measures to support their design decisions. The role of computerized building design tools is to provide such information efficiently. Given the breadth of choices and concerns that a design team is confronted with, various design aspects constantly compete for the team’s attention. To remain competitive, design professionals must weigh the value of information gained through any one simulation tool against the invested time and financial resources, as well as against the value of comparable information that might be gained through the use of other or no tools. Because daylighting is a declared design feature of
* Corresponding author. Tel.: +1 613 993 9703. E-mail address: (C. Reinhart).

virtually all ‘‘sustainable/green’’ buildings, and because it is difficult to evaluate its quality and quantity in a space through simple rules of thumb, daylighting software should have a high rate of acceptance and adoption within the market. This is the underlying notion for the development of daylight simulation tools. The research described in this paper was motivated by the authors’ observation that despite the availability of simplified and detailed daylight simulation methods, none of these tools has yet penetrated the building design market to any