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DAYLIGHTING METRICS

PROJECT OBJECTIVE

The objectives of this project were to develop a set of daylight performance metrics and criteria, in cooperation with national and international leaders in the field, which would be used in programs, codes and standards to promote successfully daylit buildings, and thus support greater energy savings and demand reduction. This project will address both energy performance and illumination standards for daylit buildings.

The Daylight Metrics project is a necessary step toward achieving widespread promotion and use of daylighting in buildings. The energy savings and demand reduction potential of daylighting are enormous, but since acceptable performance is poorly defined, current programs, codes and standards are hesitant to require daylighting.

Once daylight metrics and criteria have been developed and recognized by national stakeholder groups, they will be available to product developers, researchers, designers, program managers, building owners, etc., to evaluate performance and promote the adoption of better daylighting strategies. Without improved metrics, the market will remain confused and advancement of this field will be delayed.

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PROJECT APPROACH

A range of daylit spaces were identified for study. Each study space was then evaluated for the “goodness” of its daylighting conditions by both experts and occupants.

Three dimensional computer models were created in order to run annual simulations of the daylight illumination and resulting building energy use impacts for each space. The occupant qualitative assessments was compared to output from the simulations in order to develop quantitative metrics that capture the most useful descriptors of annual daylight performance in the spaces.

Ultimately, these newly defined simulation outputs provide more useful insight into the annual quantity and quality of daylight in spaces than the current common practice of calculating a static daylight factor or daylight illuminance levels for only a few selected sky conditions.

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PROJECT TEAM

This work was done in concert with the work of the Daylighting Metrics Committee of the Illuminating Engineering Society of North America (IES), and with input from many stakeholders to ensure that the analysis methods and output are widely applicable.  

This project is funded by the California Energy Commission PIER Program, the Northwest Energy Efficiency Alliance (NEEA). It is being run in parallel with a similar project funded by the New York Energy Efficiency Authority (NYSERDA).

Principal Investigator for both projects is Lisa Heschong, of the Heschong Mahone Group: Mudit Saxena is Project Manager. PIER team members include Professor Joel Loveland and members of the Integrated Design Lab at the University of Washington in Seattle, Washington State; Christoph Reinhart, PhD, of National Research Council of Canada, in Ottawa Canada (and starting a new teaching appointment at Harvard University); Professor Marilyne Andersen of Massachusetts Institute of Technology Department of Architecture; and George Loisos, of Loisos/Ubbelohde  Design. The NYSERDA Project team includes Energy Resources Group of New York City, in addition to Christoph Reinhart and Marilyne Andersen.

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Copyright: Heschong Mahone Group, Inc. 2007