CLTC worked with Capital Engineering Consultants, Inc. to evaluate the glare potential at the Sacramento CalPERS building. CLTC measured luminance (aka absolute brightness,) and compared the values to the Illuminating Engineering Society’s (IES) recommendations.

Measurements were taken in south-east and north-west facing interior spaces of the building, both with the existing shades up and down. CLTC used digital images and specialized software to determine the glare potential. The results for both spaces showed glare indices values and luminance ratios that were much higher than IES recommended practice.

CLTC recommended using a technique that allows quick and easy determination of when the sun is striking individual windows during different times of the year. This technique is based on superimposing a fish-eye image of the sky with stereographic sun paths over a photograph of the space, shown in the image on the left, below. This information can be used to more accurately set the shading timing in the Building Management and Control System (BMCS).

Superimposed sun paths on southern window photograph, focused on sky zenith		Luminance map of south-east office space

Suggested alternatives required additional work that was beyond the scope of the initial phase of the project, which was not extended.

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