[Bldg-sim] Window performance with frames

Sheila sheila at energyopportunities.com
Fri Jul 16 06:37:42 PDT 2010


Good morning Everyone,

 

I agree with both Andy and Alex that the installed assembly is what must be modeled because the assembly values can differ significantly from the center of glass values.  However, more often than not, the fenestration is designed using glazing from one manufacturer which is set in frames by a different manufacturer.  This creates difficulties in determining the assembly value, and modelers have a very hard time accessing testing data for a particular combination of glazing and frame.  Windows5 is often the only tool a modeler has to approximate the assembly values needed for the models.

 

When using Windows5, we never use the default frame values.  We go to the frame manufacturer to get the frame parameters including the U-value and create a custom frame for that project in Windows5.  The same goes for the glazing assembly when the data is not already in the Windows5 database.  By using the actual manufacturers' frame and glazing data, Windows5 can get close to the installed values.

 

Keep in mind that energy models can never exactly match reality.  And, there comes a point in energy modeling when we have to say "close enough".  In any model, that point is reached when the amount of time needed to get a fractional improvement in accuracy becomes burdensome with very little gained in accuracy.  Using Windows5 as outlined above can help to minimize the margin of error with a reasonable amount of effort.  

 

For EAc1 submissions, you can submit the glazing data sheet which shows the center of glass values, the data sheet (or other form of response) from the frame manufacturer, and a copy of the Windows5 report (or a snapshot of the inputs/outputs screen) showing the entire assembly calculated values.  The reviewer will accept this approach.

 

I hope this clarifies things from the energy modeling and LEED perspectives.  Have a nice day.

 

Sheila Sagerer

Energy Engineer, EIT, LEED AP

Energy Opportunities, Inc, a 7group company

Phone: 717-880-9069

www.sevengroup.com

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Andy Hoover
Sent: Friday, July 16, 2010 9:01 AM
To: 'Alex Krickx'; 'Otto Schwieterman'; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames

 

Hey all:

 

We do not know Alex at all but completely support his position that it is the entire assembly/full frame in use that counts.   We are a building envelope consultancy and deal principally in the built market and see this issue all of the time where the performance of window, storefront and curtain wall units is dramatically different than that 'calculated' or provided.   As a matter of fact, it is the unfortunate norm.  At the end of the day it is about actual in use performance and that performance versus what was calculated.  I will stay away from installation difference in this one J.

 

Anyway, we do agree with and have seen the truth to his assessment of frame differences.  It is only the performance of the entire assembly, at every level of a structure as a whole, that counts in the real world.  

 

Thanks and take care,

 

Andy 

 

Andy Hoover

Principal

The BEST Consultant, Inc.

Cell: 678-793-1159

Office: 678-200-7648

Fax: 678-827-0574

Email: andyhoover at thebestconsultant.com

Web: www.thebestconsultant.com

 

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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Alex Krickx
Sent: Wednesday, July 14, 2010 4:57 PM
To: Otto Schwieterman; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Window performance with frames

 

Hi Otto,

 

Serious Materials provides full frame performance data here: http://index.seriouswindows.com/document-library/Datasheets/. I have also have some of our commercial packages modeled in curtainwall and storefront framing systems that I can provide upon request.

 

Firstly let me say that Window5 is a great tool - I use it often and love it. The only thing I would advise is that there can be a wide distribution in frame U-factors. The default U-factor for a thermally broken aluminum (TBA) frame in Window 5 is U-1.0. Using THERM and Window5 I've seen TBA frame U-factors vary from as low as 0.8 to as high as 1.5. The resultant full-frame U-factor using these 2 differing TBA frames (and the same glass package) is: 0.29 (R-3.4) for the poorer performing frame, and 0.22 (R-4.5) for the better frame.

 

I would say that putting either of those full frame u-factors in your energy model will yield pretty different results. 

 

I think it's really important that we, as simulators and modelers, look at full-frame performance because this is the system that will be installed in the building. Center-of-Glass data can be useful comparing two different glass packages, but at the end of the day, it's a framed system that will be installed and a framed system that should be analyzed. My 2¢.

 

Regards,

Alex Krickx

 

 

Alex Krickx

Building Energy Specialist

 

1250 Elko Dr, Sunnyvale, CA 94089

(t) 408.541.8124

 

Warning: The information contained in this e-mail may be privileged attorney-client communications or attorney work product and/or proprietary and confidential.  If the reader of this message is not the intended recipient then you have received it in error and any review, distribution or copying of this message is prohibited and you are to notify us immediately by reply e-mail and delete the original message immediately.

 

 

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Otto Schwieterman
Sent: Wednesday, July 14, 2010 1:10 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Window performance with frames

 

Does anyone know of a window manufacturer web site that has literature on its windows including the frame? I am using Trace 700 for EA Credit 1 and the reviewer asked for manufacturer data sheets for window performance values (U-value, VLT and SHGC) including the frame. 

 

Your help is appreciated,

 

Otto

 

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