[Equest-users] LEED Fenestration Modeling Question

[James Hess]

FYI, another practical way to account for the effects of the framing is to use the charts provided by the curtain wall framing manufacturers.

For example, here is the detailed catalog for the Kawneer system 1600 type 1:

http://www.kawneer.com/kawneer/north_america/catalog/pdf/1600_Wall_Sys1__E--A.pdf

The charts and data (from pages 32) on allow us to estimate overall u-value and SHGC based on center of glass values and the ratio of Vision Area to Total Area (%).

It’s fairly straightforward to document the Vision Area, but a very good rule of thumb is 90%.

For example, if we had glass with a COG U-value of 0.28 and 90% Vision Area (i.e. 10% framing), the overall/System/Assembly U-value would be ~ 0.44

My experience is that this is completely acceptable for LEED/GBCI.  These charts were created by application engineers working for the framing companies, which I’m assuming they know this stuff way better than I do.   If you look at page 35, it says the U-factors, SHGC, and VT values are determined in accordance with NFRC 100 and 200.

Other framing vendors, like EFCO, have similar charts that we can use.

In my view, this is good enough to document assembly performance.  I would use the charts and move on.  If the new Table 1.4 includes space for a comment, I would reference the charts, and submit the charts if asked.

There really is no other way to do this except try to calculate ourselves, which why bother when we have these charts.  If we ask the architects, often times, they will not understand what we are asking for.  They will probably only be familiar with the glass properties, not the combination of glass + framing.  The glass vendor will only give you performance data for the glass, not the combination of glass and framing.  I’m not sure why section 5.8.8.2 exists, except for packaged windows.  I haven’t found anybody that will give you a permanently installed nameplate or official certification for the entire fenestration system, at least for custom systems often encountered in commercial construction (i.e. curtain wall versus packaged windows).  Maybe the 5.8.8.2 requirement are met in other parts of country by somebody, but for now, I’ve found these charts from the curtain wall vendors to be very effective from a cost and time standpoint.

I would welcome any additional feedback on this.

Hope this is helpful.

Thanks!  ☺

Regards,

JAH

James A. Hess, PE, CEM, BEMP
Energy Engineer
TME, Inc.
Little Rock, AR
Mobile: (501) 351-4667

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
Sent: Monday, April 15, 2013 2:34 PM
To: Bishop, Bill; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] LEED Fenestration Modeling Question

Thanks Bill, the comment you received is encouraging.

Paul Diglio, CEM, CBCP
87 Fairmont Avenue
New Haven, CT 06513
203-415-0082

www.pdigliollc.com<http://www.pdigliollc.com>


________________________________
From: "Bishop, Bill" <bbishop at pathfinder-ea.com<mailto:bbishop at pathfinder-ea.com>>
To: Paul Diglio <paul.diglio at sbcglobal.net<mailto:paul.diglio at sbcglobal.net>>; "equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>" <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Sent: Mon, April 15, 2013 2:45:18 PM
Subject: RE: [Equest-users] LEED Fenestration Modeling Question
Paul,

I recently received the following comment in a LEED review for a LEED-NC v2009 project:
[cid:image001.png at 01CE3A8A.7FFABE00]
This implies that Window v6.3 calculations are acceptable in lieu of NFRC ratings. The comment does not exclude the modeler from performing the calculation.
Of course, I have no idea if this is boilerplate language or if LEED reviewers have discretion here. It is also possible that requirements will become stricter for newer projects.

Regards,
Bill

William Bishop, PE, BEMP, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

134 South Fitzhugh Street                 Rochester, NY 14608
T: (585) 325-6004 Ext. 114            F: (585) 325-6005
bbishop at pathfinder-ea.com<mailto:wbishop at pathfinder-ea.com>           www.pathfinder-ea.com<http://www.pathfinder-ea.com/>
P   Sustainability – the forest AND the trees. P

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul Diglio
Sent: Monday, April 15, 2013 2:34 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] LEED Fenestration Modeling Question

Folks:

I am a bit confused when modeling unrated vertical fenestration for the proposed model.  90.1 states that we need to use the values determined in accordance with NFRC 100 or we can use the data in Table A8.2 for vertical fenestration per Exception b, Section 5.8.2.4.

If so, the values in Table A8.2 exceed the maximum allowed fenestration u-values listed in Table 5.5-5 (my zone), so will this not disqualify the proposed building model?

I have often found it impossible to get the architect to supply the NFRC assembly ratings of the glazing and field erected curtain-wall systems.

I have used the LBNL Window 6.3 program to calculate the vertical fenestration ratings, but 90.1 Section 5.8.8.2 states that the fenestration product shall have a permanently installed nameplate or the manufacturer shall provide a signed and dated certification for the installed fenestration.

I don't see any wiggle-room where 90.1 allows the modeler to calculate the NFRC rating of vertical fenestration.

Saying that, I have submitted projects where I calculated the fenestration assembly u-values without any kick-back from the GBCI.

I am concerned that the reviewers will push this issue since it is now clearly defined on the new Section 1.4 Table and if I submit my own ratings I will end up remodeling the project and/or the proposed building envelope will be rejected since it doesn't meet the mandatory requirements of Section 5.4.

Any thoughts?

Thank you,

Paul Diglio, CEM, CBCP
87 Fairmont Avenue
New Haven, CT 06513
203-415-0082

www.pdigliollc.com<http://www.pdigliollc.com>

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