Research Project Information

Research Project Summary Information

Hybrid Skylighting System:Hybrid Skylighting Systems(ST5059-1)

Rensselaer Polytechnic Institute-LRC


There are examples of cost savings and quality lighting in spaces lit by skylights integrated with artificial lighting systems, but information on the costs and performance of hybrid skylighting systems is limited, and the general public is reluctant to install skylights due to the poor performance of early models. To increase use of daylighting as a light source, the Lighting Research Center (LRC) proposed to develop a hybrid skylight design that would be responsive to commercial and industrial customers' needs and to make the design publicly available.

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Project Description

The project (1) conducted market research of customers' satisfaction with existing skylighting systems, (2) developed and tested four prototype hybrid systems, (3) developed a performance specification for hybrid skylighting systems, (4) built and tested a full-scale prototype, and (5) wrote an installation guide for hybrid skylighting systems. The prototype systems were installed and field tested in the Lightolier Distribution Center in Norwich, Connecticut.


Use of the hybrid skylight reduced energy consumption by 40% compared to the previous metal halide lighting. Savings are related both to dimming controls and the use of more efficient lamps. Controls provided energy savings of 28%. Energy savings, associated with eight months’ use of three hybrid skylights, resulted in environmental savings of 11.7 lbs. of SO2, 3.6 lbs of NOx, and 2,802 lbs. of CO2.

Project Results

The hybrid skylight was easy to commission and when sufficient daylight was present, the hybrid skylight turned off the electric lighting rather than maintaining a minimum dim level. Some design improvements to the prototype designs are necessary prior to commercialization. The joints and seals of the sunlight diffuser box need to allow for thermal expansion and contraction while retaining the seal; if continuous dimming is used, a "knife-edge" socket may be more reliable to prevent premature lamp failure and end-darkening; tandem wiring should be avoided when using dimming ballasts to avoid premature lamp failure. Surveys showed that employees preferred the hybrid skylighting system to the metal halide luminaries they replaced, and two-thirds of the employees said they would like to see the hybrid skylight installation extended to the rest of the facility. The results of the field test were published in a Field Test DELTA Publication (under NYSERDA agreement 7035) and made available in hard copy format to interested parties and in electronic format over the LRC Web site. The LRC is actively seeking manufacturers to commercialize the hybrid skylight designs.


Rensselaer Polytechnic Institute-LRC
21 Union St
Troy, NY 12180

Principle Investigator

Russell Leslie

Universities Involved

Rensselaer Polytechnic Institute


Project Type:

Product Development

Technologies Types:

Building Systems

NYSERDA Contact Information

Marsha Walton


R&D - Buildings Research

Contract Details

Start Date: 1/11/2010
Project Status: Active
Contract Number: ST5059-1

Last Updated: 3/5/2012 1