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Diffuse Glazing TG Spring 2019

This article discusses updates to diffuse glazing, including a Request for Proposal (RFP), editorial clarifications, and the use of obscure glass in determining U-factors. It also highlights the challenges and cost considerations associated with diffuse glazing research projects.

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Diffuse Glazing TG Spring 2019

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  1. Diffuse Glazing TG Spring 2019 Jacob Jonsson

  2. Agenda • Ballot comments • Split between obscure and diffuse updates • Editorial clarifications to Obscure path • Updates to 600 are done by staff • Diffuse glazing RFP • ILC • Modelling • Software updates • LBNL experience with the UL 270 integrating sphere • Works • Large

  3. Obscure glazing comment NFRC 100 • 1) 4.2.5.H modified language removes fritted or wired but leaves including obscure glass . It appears redundant to have the language read:  For the purpose of determining U-factors, only glazing tint and/or obscurity (including obscure glass) shall be permitted to be assumed to have the same U-factor • Recommend language modification (that does not change the intent):  For the purpose of determining U-factors, only glazing tint and/or obscure glass shall be permitted to be assumed to have the same U-factor • More concise, not obvious that it changes the meaning • The new definition in this ballot covers all intent of what obscurity  can include in the document or for the purpose of assuming clear glass. And the recommended language is written similarly to the balloted language in NFRC 200, section 4.5.G:  Ratings for products with obscure glass shall be deemed to be equivalent to the ratings for clear glass   • 2) All new or revised definitions need to be provided in the NFRC 600 document. • 600 document maintained by staff, no member vote required

  4. Obscure glazing comment NFRC 200 • 1) Editorial: 4.5.G: Remove the word  “and”  at the end of the balloted sentence (language shown is as balloted):  Ratings for products with obscure glass shall be deemed to be equivalent to the ratings for clear glass; and   • The ballot is not changing the use of the word “and” it is just how the list is organized. Definitely hard to see that this is substantive

  5. Diffuse Glazing RFP • Research project to capture and formalize the TGs work as well as extend in areas where the TG had limited resources • ILC with more than 1 product • Validate IR work done by Viracon for rough surfaces • Set up raytracing models of ILC products

  6. Diffuse Glazing RFP • > I do have one question, however. The estimated cost of $120k strikes me as rather high. I concede that I’m not overly familiar with all the details of such a project. However, if manufacturers will be providing the test samples (at no charge), and ILC participants will be conducting the measurements (at no charge), what else is there that will cost $120k?     There are three things that make this a larger project larger than a regular ILC (the last one was $50k). 1.    Part of the proposal is for  FTIR integrating sphere measurements. Part of this will include sending     samples for characterization at NIST which will not be free of charge. These FTIR integrating spheres are less standardized than the instruments used in our regular ILC so understanding/explaining why results differ is harder. 2.    The ray-tracing and modeling part is involves substantive work. Research it will include goniophotometer measurements of all the samples which is additional work vs regular ILC.     3.    There is an objective to develop a new data format and update WINDOW to parse the new format which requires programmer time.

  7. RFP ILC comment from LBNL • Comparing the diffuse ILC with the specular, there are also three points that make it more challenging: a.    Measuring the diffuse component will add a new metric     where we are not familiar with spectral shape of the result.     Without the knowledge of how the material behaves we expect     it to be much harder to reconcile any differences we see. b.    New data format adds confusion to the submitters (instruments     measure total and diffuse, but we ask for diffuse and specular     to be reported for international harmonization). c.    The number of samples selected (will be done by committee)     will be larger than for the regular ILC. As this is the first     time we verify these instruments, we will want to make sure we     exercise all the new rules to show that it is valid for the most prevalent product on the market, but also any edge  cases. This increases analysis time.

  8. UL 270 integrating sphere

  9. First impressions • Not switchable by one person (for most persons) • Large sample compartment • No calibrated diffuse reference included • Software control of Reflectance and Transmittance not intuitive, but consistent and repeatable • Good results for R and T of specular samples • Agreement with others on the special TG sample

  10. Baselines

  11. Specular sample compared to l950

  12. Diffuse TG laminate sample

  13. Diffuse TG sample

  14. Diffuse TG compare

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