Rapid field testing of low-emittance coated glazings for product verification

TitleRapid field testing of low-emittance coated glazings for product verification
Publication TypeConference Paper
Year of Publication1998
AuthorsBrent T Griffith, Christian Kohler, Howdy Goudey, Daniel Turler, Dariush K Arasteh
Conference NameASHRAE/DOE/BTECC Conference, Thermal Performance of the Exterior Envelopes of Buildings VII
Date Published12/1998
Conference LocationClearwater Beach, Florida
Call NumberLBNL-41352

This paper analyzes prospects for developing a test device suitable for field verification of the types of low-emittance (low-e) coatings present on high-performance window products. Test devices are currently available that can simply detect the presence of low-e coatings and that can measure other important characteristics of high-performance windows, such as the thickness of glazing layers or the gap in dual glazings. However, no devices have yet been developed that can measure gas concentrations or distinguish among types of coatings. This paper presents two optical methods for verification of low-e coatings. The first method uses a portable, fiber-optic spectrometer to characterize spectral reflectances from 650 to 1,100 nm for selected surfaces within an insulated glazing unit (IGU). The second method uses an infrared-light-emitting diode and a phototransistor to evaluate the aggregate normal reflectance of an IGU at 940 nm. Both methods measure reflectance in the near (solar) infrared spectrum and are useful for distinguishing between regular and spectrally selective low-e coatings. The infrared-diode/phototransistor method appears promising for use in a low-cost, hand-held field test device.

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