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CS-2009 EAp2:Minimum Energy Performance

U-factor for fenestration in the Proposed Model

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Ron Dean
Sumac Inc.
LEEDuser Basic Member
20 thumbs up

Hello everyone, I'm in the process of filling out the table 1.4 for LEED EAp2 submission, my question is about this ''How were the Proposed case framed assembly fenestration U-factors determined?'' along with the following options: * NFRC testing for site-assembled fenestration * NFRC testing for manufactured fenestration assemblies * Table A8.2 (windows) and Table A8.1 (skylights) * LBNL Window 5 or Window 6 calculations * Energy simulation includes separate frame and glazing Normally the U-value I have for the projects I'm working on doesn't include framing, just the glazing (please confirm if this always happen in the technical sheet of the glazing). Please help me figure out the meaning of the previos options and give me a big picture about how different would be considering the framing in relation to not considering it. Thanks in advance.

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Mon, 07/01/2013 - 13:36

The impact depends on the framing material and construction. You could have a U0.27 for the glazing and a U0.45 for the whole assembly with a metal framed window. Most modeling software allows you to model the framing material separate from the glazing. So you don't need to know the framing U-value as there are choices in the library that should be close to what you are using. Pick the framing material and enter the glazing data. You should also be able to check with the window manufacturer to get assembly U-values which would be a good reality check against your modeling values.
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Ron Dean
Sumac Inc.
LEEDuser Basic Member
20 thumbs up

Thu, 07/04/2013 - 19:43

Thanks for your reply Marcus. I've asked a manufacturer about this issue and told me that they don't provide the properties for the whole assembly (glazing, frames and dividers), just for the glazing. So, I guess the others would tell me the same, therefore I prefer this option: Energy simulation includes separate frame and glazing. However, I still don't understand the difference between these two options: * NFRC testing for site-assembled fenestration * NFRC testing for manufactured fenestration assemblies Please advice. Thanks in advance.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Mon, 07/08/2013 - 13:55

It is very unusual that the window manufacturer would refuse to provide the window performance data. We like to get it to confirm and double check the modeling results we get when modeling the framing and glazing. The NFRC testing is something that the manufacturer obtains by submitting sample windows for testing to a qualified lab. I would guess that the first one is for systems like curtainwall that are assembled on-site and the second one is for windows made in a factory.
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Ron Dean
Sumac Inc.
LEEDuser Basic Member
20 thumbs up

Mon, 07/15/2013 - 21:57

Thanks again Marcus, 1. I've been looking up and found this link http://search.nfrc.org/search/searchDefault.aspx, in which there is a list of glazing manufacturers approved by NFRC. The three manufacturers I usually work with are not on that list; so does anybody know a similar link for the standard EN410 or other similar entity so that I can certify that the manufacturers have their products tested by a third recognized party? 2. I've also seen in the NFRC webpage examples of glazing with a film; it helps reduce the SHGC and VLT factors (not the U-value). This would be a great option to offset the high WWR for many projects I work on. So, is there a way to obtain the SHGC and U-factor by calculations? (I ask this because it's possible that the manufacturers cannot provide these proporties for the assembly) Thanks in advance.
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Tue, 07/16/2013 - 13:34

I am not familiar with the window industry in the EU but one of those three manufacturers should be if they do business there. You can use Window 6 software for the U-value - http://windows.lbl.gov/software/window/6/ You can measure the SHGC/VLT with a meter. VLT - http://edtm.com/index.php/sales-tools-for-window-and-film/visible-light-meters/tint-meter-vlt-with-thermometer-vp1165 SHGC - http://edtm.com/index.php/sales-tools-for-window-and-film/energy-performance-meters/window-energy-profiler-wp4500 If you know the SHGC and VLT of the glazing you can use that in your model. Whole unit values only matter if you are not modeling the frames separately. For a window film you can roughly determine the combined SHGC by knowing the SHGC of the film and the glass it is being applied to. Multiply one times the other and you will have a very rough combined value. I would consult with the window film manufacturer.

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