Measurement of Directional Optical Properties of Coated Glazing Products for Building and Automotive Applications

Mr. Peter A. van Nijnatten

The optical properties for most marketed
glazing products are, according to the present
standards, quoted only for a zero angle of
incidence. This raises a problem since in reality
daylight and solar radiation enter a window under
all angles and modern building simulation tools
rely on the availability of data on directional optical
properties of glazing. This paper discusses the
practical problems involved with measurement of
optical properties of glazing at oblique incidence
and gives recommendations for measurement
procedures. The recommended procedures are
intended to be suitable for use by the buildings
and automotive industries to enable more
comprehensive product performance specification
and allow independent and industrial research
laboratories to perform accurate directional
measurements in an unambiguous way.

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