1. Fritted Glass TG – Spring 2016 Jacob C. Jonsson Windows and Envelope Materials Group Building Technology and Urban Systems Division

2. SCOPE and Members  Find a way to obtain spectral data for fritted glass in a manner that would allow WINDOW calculations of IGUs.  Determine best practice how to obtain data and verify the accuracy of these practices.  TG: Jason Theios, Dan Wacek, Jacob Jonsson, Helen Rose Wilson, Mike Buchanan, Ben West, Michael Hawkings, David Cooper, Joe Richard, Mike Thoman, Paul Bush, Jen Padgett 2

3. Get scattering samples with a trusted result  Started with fritted glass, but sample inhomogeneity made it hard to get repeatable measurement results  Viracon fabricated three laminates with a diffuse interlayer each at 11.75" x 7.75" with tin surfaces to be exposed.  12 mm OptiWhite (low iron)+0.030“ Saflex Arctic Snow (transluscent white)PVB+3 mm Optiwhite float glass  High transmittance, VT~0.65, R & A ~ 0.17 3

4. Instrument parameters  Guardian 270 mm integrating sphere, special designed attachment for Perkin-Elmer 1050 spectrophotometer  100 mm aperture  Beam size ~ 10 mm by 20 mm  Can measure oblique angles of incidence as well as at near normal 4

5. Transmittance at 8 degrees angle of incidence  Both R and T were measured at 8 degrees angle of incidence to get accurate absorption calculations  10mm expected to be lower, longer travel more light loss 5

6. Reflectance at 8 degrees angle of incidence  I would have expected 10mm to be lower here but it is higher for all samples  Longer distance would increase glass absorption and larger light loss  L2 higher for both R and T 6

7. Absorption (+ light loss) based on orientation - vis  Absorption 3 mm was based on T measurement orientation, i.e. A3mm = 1-T3mm-R10mm  Since R3mm A3mm 7

8. Absorption (+ light loss) based on orientation - NIR  Difference decreases with longer wavelengths  Would be consistent with reduction in scattering and less light loss and less glass absorption 8

9. Next Step  Jason Theios (Guardian) to send samples to labs.  LBNL and Fraunhofer ISE to measure L1 and L3 using goniophotometers  Compare goniophotometer data with spectrophotometer data  Optimistic goal to have something in 2 months 9