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Measurements and Comparisons of Lightshelf Performance in Two Texas Office Buildings
Abstract
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.
Citation
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 https : / /hdl .handle .net /1969 .1 /6470.