Visual Comfort Analysis of Innovative Interior and Exterior Shading Systems for Commercial Buildings using High Resolution Luminance Images Page: 3 of 26
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Visual Comfort Analysis of Innovative Interior and Exterior
Shading Systems for Commercial Buildings using High
Resolution Luminance Images
K.Konis, E.S.Lee, R.D.Clenr, Ph.D
BuildIng Technoloeies Program, Environynenetl Energy rechnalogies Diisiont, utv'Lawce Berkeley
Naioned LaborarorY, Maiistop 90-3 , 1 Cyclorron Road. Berkeley, CA 94720, USA
The objective of this study was to explore how calibrated high dynamic range (HDR) images (luminance
maps) acquired in real world daylit environments can be used to characterize, evaluate, and compare visual
comfort conditions of innovative facade shading and light-redirecting systems. Detailed (1536 x 1536
pixel) luminance maps were time-lapse acquired from two view positions in an unoccupied full scale
testbed facility. These maps were analyzed using existing visual comfort metrics to quantify how
innovative interior and exterior shading systems compare to conventional systems under real sun and sky
conditions over a solstice-tc-soIstice test interval. The results provide a case study in the challenges and
potential ofrmethods of visualizing, evaluating and summarizing daily and seasonal variation ofvisual
comfort conditions computed from large sets of image data.
Keywords: daylighting, high dynamic range imaging, discomfort glare.
In recent years, mainstream acceptance of the "green building movement" has led to the construction of a
significant n um ber of build ings with highly glazed facades, designed with the dual goals of 1) comp lying
with green building certification programs (e.g., LEED daylight and vicw credits) and 2) the reduction of
electrical lighting energy consumption via daylighting. Casual inspection of these buildings in operation
often reveals that shading systems are routinely deployed by occupants to maintain comfortab le visual
conditions, reducing the potential for lighting energy reduction as well as visual connection to the exterior.
This study focuses on evaluating the visual comfort conditions produced from a number ofinnovative interior
and exterior facade shading and light-tedirect ing systems that have the potential to more effectively balance
the goals of visual comfort with daylight transmission in comparison to conventional shading sysrns (e.g.
manually operated Venetian blinds or roller shades) used in typical sidelit perimeter zones. In this study, the
term "innovative" refers to systems that ernploy one or more of the Following arsegies; sub-division of the
window wall into an upper daylighting zone and a lower "view" zoneoptical liglit redirection, translucent
materials, and automation of slat angle and/or height adjustment.
Prior to the availability ofluminance maps to assess lighting conditions in real spaces, the limitations of
available photometric nionitoringequipnent (e.g., shielded illuminance sensors, spot luminance meters)
resulted in simplified methods of glare assessment in daylit spaces. Average luminances of large window
areas using shielded sensors have commonly been used 10 compute the daylight glare index (DGI) [lEA SHC
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Konis, Kyle; Lee, Eleanor & Clear, Robert. Visual Comfort Analysis of Innovative Interior and Exterior Shading Systems for Commercial Buildings using High Resolution Luminance Images, article, January 11, 2011; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc833640/m1/3/: accessed May 27, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.