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Measurements and Comparisons of Lightshelf Performance in Two Texas Office Buildings
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Natural light (daylighting) in office buildings is often used to supplement or eliminate the artificial lighting otherwise required. When daylight can be effectively admitted and distributed, then energy is conserved, and the dependence on electric lighting is reduced. Traditional means of admitting day light in offices are windows, skylights, atrium, lightcourts, and lightshelves. This study involves two significant Texas office buildings: Lockheed Company's Facilities Systems Division In Austin and Shell Oil Company's Woodcreek Offices near Houston. Both of these Installations have used lightshelves to aid in energy reduction. The Lockheed building was designed with the lightshelf locations determined by the orientation of the various facades and open Light courts. On the other hand, the Shell facility was conceived and built on the concept of lightshelves and uses them on every facade, both on the exterior and interior of the building and around their many covered atriums . This paper compares and contrasts the lightshelves In these two installations based on a number of criteria. Specific considerations at each location include the orientation of the glazed wall with the Lightshelf, the magnitude of the external Illumination at the noon equinox times of measurement, and the effectiveness of each system at daylight distribution at various depths from the glazing. The reduction effect of atrium/light court configurations is also considered. Graphics and empirical data are included which Indicate these factors as well as various brightness ratios and subjective assessments which serve as an indication of lighting quality for each facility. Finally, tentative conclusions are drawn based on the field data which indicate the effectiveness of each lightshelf system and lightshelves in general. Additional suggestions are made regarding alterations to each installation which could make each one more effective at daylight distribution as well as maximizing energy savings.
Molinelli, J. F.; Boyer, L. L. (1987). Measurements and Comparisons of Lightshelf Performance in Two Texas Office Buildings. Energy Systems Laboratory (http://esl.tamu.edu); Texas A&M University (http://www.tamu.edu). Available electronically from