Required Indoor Environmental Quality Guidelines
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I.9 Daylight
Intent
Provide daylight for ambient illumination at levels and conditions known to produce physiological and psychological benefits. Daylight contributes to a perception of a 'bright and cheery' workplace through provision of volumetric brightness (also called "room-surface brightness".) The important qualities of daylight are its inherent variation, power spectrum (color), and the predominantly horizontal component of its illumination vector (direction of illumination.) Some studies have also shown a correlation between daylighting and improved productivity and test scores.
Required Performance Criteria
A. At least 75% of the floor area of continuously occupied spaces in the building shall have a minimum daylight factor of 1% when measured without furniture and at 2'6" above the floor. This may be demonstrated using the Daylight Factor Calculator provided in the guidelines, through daylight simulation, or physical daylight modeling.
B. In every continuously occupied space with daylight, not more than 15% of the floor area shall exceed a uniformity ratio of 10:1 when measured without furniture and at 2'6" above the floor.
C. To be considered a good daylighting design, direct solar penetration must be controlled with fixed or operable shading devices and kept from falling on the work plane beyond 4 ft from the exterior walls during most operating hours.
D. Automatic controls should be employed to turn off or dim the electric lights when daylighting is available.
Note: For spaces with daylight the Window to Floor Area Ratio (WFAR) should not need to exceed 25% in order to meet daylighting criteria listed here. Note that exceeding this WFAR may introduce excess energy use and possibly glare.
Compliance Tools and Resources
- Daylighting Factor Calculator See Appendix I-3.
- For more advanced and refined analysis, using physical models is one very effective way to analyze daylighting performance of a building. Even the simplest foam core models will inform the design team about how the behavior of daylight changes as building parameters are varied. Daylight apertures and reflectance values of material surfaces must be accurately modeled for valid results. Such daylighting models can then be tested on site or under artificial sky conditions in a daylighting laboratory to determine daylight factors. Sundials attached to the model base allow such models to be tested so as to simulate annual variation of direct sunlight.
- In addition, also for more advanced and refined analysis, computer analysis and simulation may be used to generate a daylighting solution. Some widely available programs are noted below. Usually, three-dimensional digital models are constructed using (CAD) computer-aided design software that is then imported into the lighting software. Such programs usually require the user to define location, sky conditions, and date and time and interior surface characteristics. Some programs produce lifelike renderings of the design but do not provide accurate quantitative results.
Related MSBG Documents
- Form P-5 Indoor Environmental Quality Documentation
- Appendix I-1 Suggested Implementation for all Indoor Environmental Quality Guidelines
- Appendix I-3 Daylighting Factor Calculator
Supplemental Resources
The US Department of Energy and its associated national laboratories and their outreach programs are rich sources of information and simulation and analysis programs for daylighting. Among these are
- ADELINE (Advanced Daylighting and Electric Lighting Integrated New Environment) at www.ibp.fhg.de/wt/adeline/, which "provides architects and engineers with accurate information about the behavior and the performance of indoor lighting systems. Both natural and electrical lighting problems can be solved, in simple rooms or the most complex spaces."
- Radiance. radsite.lbl.gov/radiance/, The primary advantage of Radiance over simpler lighting calculation and rendering tools is that there are no limitations on the geometry or the materials that may be simulated. Radiance is used by architects and engineers to predict illumination, visual quality and appearance of innovative design spaces, and by researchers to evaluate new lighting and daylighting technologies..
- EREC Reference Brief "Daylighting for Commercial, Institutional an d Industrial Buildings" www.eere.energy.gov/consumerinfo/factsheets/cb4.html an excellent introduction to daylighting fundamentals.
- DOE Buildings Program: Daylighting www.eere.energy.gov/buildings/info/design/integratedbuilding/passivedaylighting.html for everything you ever wanted to know about daylighting, and more.
- Efficient Windows Collaborative www.efficientwindows.org contains references, resources and simulation tools for window design and selection for daylighting.
- An entire course in daylighting is provided by the online available Vital Signs Curriculum Materials Project by Marc Schiller and Schweta A. Japee (both at the University of Southern California School of Architecture): "Interior Illuminance, Daylight Controls, and Occupant Response." It is "a complete range of exercises covering everything from an understanding of how your eye works to how to do image processing on a digitized video scan."
Other Supplemental Resources:
- Baker, Nick, & Steemers, Koen (2002) Daylight Design of Buildings: A Handbook for Architects and Engineers. James & James, Publishers.
- Bechtel, Robert B. & Churchman, Azra, (Eds.) (2002) Handbook of Environmental Psychology. John Wiley & Sons, NY.
- Boff, K. & Lincoln, J. (Eds.) (1988) Engineering Data Compendium: Human Perception and Performance. Harry G. Armstrong Aerospace Medical Research Laboratory, Wright Patterson AFB, Ohio.
- NASA (1995) Man-System Integration Standards. Johnson Space Center, Houston, TX. msis.jsc.nasa.gov
- Rea, Mark S. (Ed.) (1999) The IESNA Lighting Handbook: Reference & Application. Illuminating Engineering Society of North America, NY.
- Watson, Donald. Crosbie, Michael. Crosbie, Michael J. & Callender, Michael H. (1997.) Time-Saver Standards for Architectural Design Data. McGraw-Hill, NY.