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Daylighting Resources - Toplighting Strategies

How Much Energy do Different Toplighting Strategies Save? PDF - (2005): Final report on the study of skylight strategies and glazing types on the total yearly energy loads.

Integrated Skylight Luminaires (2003) installed in a warehouse prove to save energy and improve occupant satisfaction using self-commissioning technology that automatically dims or switches the lamps in response to daylight.


Title: Innovative daylighting: Review of systems and evaluation methods
Author(s): Littlefair, PJ
Reference: Littlefair, P.J. (1990). Innovative daylighting: review of systems and evaluation methods. Lighting Research and Technology 22(1), 1-17.
Abstract: A survey of advanced daylighting technologies, including sun-gathering heliostat-lightpipe systems, light shelves, prismatic and holographic glazing. This report finds that heliostat systems are ineffective for general illumination; a 2m (6’) diameter mirror would produce only as much useful light as seven 1.5m (5’) fluorescent tubes, and would only work when the sun shines. Light shelves are found to be effective at increasing the light level at the back of a room, but only when the sun shines; otherwise they reduce the total amount of daylight in the room. Blinds are still required in addition to light shelves, to block low-angle winter sun. In general, light-gathering and redirecting systems are found to reduce the total amount of daylight entering a space, although they subdue glare from direct sunlight, and redirect diffuse light onto surfaces around the window to reduce window glare.

Title: Advanced optical daylighting systems: Light shelves and light pipes
Author(s): Beltran, LO, Lee, ES, Selkowitz, SE
Reference: Beltran, L.O., Lee, E.S. and Selkowitz, S.E. (1997). Advanced optical daylighting systems : light shelves and light pipes. Journal of the Illuminating Engineering Society of North America, 26(2), 91-106
Abstract: This study gives numerical values for light levels and potential lighting energy savings for several daylight redirection systems. These included single and multi-level light shelves with both matt and specular top surfaces, and sealed specular ‘light pipes’ hidden within the ceiling void. All systems were intended to reduce light levels near the window and redirect light to the back of the space. Calculations under one year of ‘average’ skies, i.e., a statistically typical combination of sunny and overcast conditions, showed that standard clear glass windows gave the highest light levels and highest potential lighting energy savings. Prismatic light pipes gave the second highest energy savings, and light shelves the lowest. Of the light shelf designs tested, the ‘base case’ design gave highest potential lighting electricity saving. Under sunny skies, all the specular light shelves and light pipes were effective at increasing light levels at the back of the space, compared to standard clear glass windows. The light pipes used in the study take up a significant proportion of the ceiling void and would necessitate unorthodox HVAC ducting.

Title: Skylighting Guidelines (Chapter 8)
Publication Organization: Heschong Mahone Group, for the Northwest Energy Efficiency Alliance
Publication URL:
Abstract: This report gives practical design guidance on the use of skylights. It gives numerical information on illumination patterns and likely energy savings by region, glazing type, building type and control type, all presented in graphical form. This report is targeted towards designers and building owners in four Pacific-Northwest states: Oregon, Washington, Idaho and Montana. It reviews the climate of the region, differing energy-code requirements in the separate states, and common building practices that affect the specification of skylights for commercial buildings.

Title: Retail skylighting knowhow
Publication Organization: Design Lights Consortium
Publication URL: http://www.designlights.org/downloads/skylighting_Retail.pdf
Abstract: This guide shows how to use skylights in retail environments to enhance a store''s appearance, attract and retain shoppers, and produce savings on lighting energy costs. The guide is illustrated with sample retail layouts, and describes how skylights can be integrated with electric lighting and lighting controls to maximize energy savings. Estimated energy savings are given for each skylighting option. Systems optimized for the northeastern United States are described in detail, and the guide cites research that finds evidence of increased retail sales in stores with skylights.

Title: Classroom lighting knowhow
Publication Organization: Design Lights Consortium
Publication URL: http://www.designlights.org/downloads/classroom_guide.pdf
Abstract: This guide provides some advice on how to use photocell dimming in schools to save lighting energy without creating distraction to students. It also provides guidance on what types of luminaries to use, and how best to orient and group them in order to maximize energy savings. Estimated energy savings are given for a variety of luminaire and control options. The guide intends to “promote high-quality learning among children … via the utilization of energy-efficient applications such as daylighting and lighting controls.” (Ref: http://www.designlights.org/downloads/classroom_guide.pdf). To this end it cites research which claims that students in well daylit schools score better in exams than those in poorly daylit schools.

Title: Warehouse skylighting knowhow
Publication Organization: Design Lights Consortium
Publication URL: http://www.designlights.org/downloads/skylighting_Warehouse.pdf
Abstract: This guide shows in detail how to design skylights and daylight—linked controls in warehouses to increase energy cost savings, productivity, and worker safety while reducing maintenance costs. The guide shows how to analyze skylight designs using software such as “SkyCalc” and it gives estimated energy savings for a variety of design options. It compares the performance of metal halide and fluorescent lamps, provides illustrated equipment layouts, and addresses construction concerns.

Title: Field Test Delta: Integrated Skylight Luminaire
Publication Organization: Lighting Research Center
Publication URL: www.lrc.rpi.edu/programs/delta/pdf/fieldtestdelta.pdf
Abstract: High-bay warehouses, light industrial facilities, and big box retail stores offer the opportunity to save energy and improve occupant satisfaction by admitting daylight through their roofs. Prototypes of an Integrated Skylight Luminaire (ISL) were installed in a working warehouse and analyzed for energy savings and lighting quality. Each ISL includes a skylight, fluorescent luminaires, and a self-commissioning control system that automatically dims or switches the lamps in response to daylight. The ISL’s design and field performance are documented. Use of the ISL was shown to reduce energy consumption by up to 40%.

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California Energy Commission
Connecticut Light & Power
Efficiency Vermont
Lighting Research Center
North Carolina Daylighting Consortium
Northwest Energy Efficiency Alliance
US Department of Energy