[Bldg-sim] Glass center-of-glass to assembly U-Value?

Michael Tillou michael.tillou at gmail.com
Thu Sep 25 07:00:33 PDT 2008


Josh,
 
I have had some luck using the pre-defined values in the tables people
mention.  The problem is that the ratio of frame area to total window area
is so variable that I don't think there is a good rule of thumb to use. 
 
Here is some data based on some recent modeling projects.
 
large curtain wall and store front systems have between 5-25% frame area
punch-out windows have between 18-40% frame area (lower percentage for
fixed, higher for operable)
 
You can see that there is a wide range which could significantly impact the
accuracy of an energy model.  In my opinion, not accounting for window frame
area properly can lead to dubious energy modeling results, especially if
you're doing comparisons between different glazing choices.
 
Mike
 
Michael Tillou, PE, LEED
Tillou Engineering, LLC
Williamstown, MA 01267
P: 413-458-9870 C: 413-652-1087
 

  _____  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Josh Greenfield
Sent: Monday, September 22, 2008 3:23 PM
To: Zeng, Ming; bldg-sim at lists.onebuilding.org;
equest-users at lists.onebuilding.org
Subject: Re: [Bldg-sim] Glass center-of-glass to assembly U-Value?



ASHRAE 90.1-2004 Section 5.8.2.5 exception (b) allows the SHGC/SC
center-of-glass to be an acceptable alternative for determining compliance
with the SHGC/SC requirements for the overall fenestration area.

 

 

 

Josh Greenfield, PE, LEED AP
Senior Associate
Primera Engineers, Ltd.
100 S. Wacker Drive, Suite 700
Chicago, IL 60606
312.606.0910 Main
312.242.6392 Direct
312.606.0415 Fax
 <blocked::mailto:jgreenfield at primerachicago.com>
jgreenfield at primerachicago.com
 <http://www.primerachicago.com> http://www.primerachicago.com

Be Green...please consider the environment before printing this email.

From: Zeng, Ming [mailto:mzeng at leoadaly.com] 
Sent: Monday, September 22, 2008 1:09 PM
To: Andrew Craig; Josh Greenfield; bldg-sim at lists.onebuilding.org;
equest-users at lists.onebuilding.org
Subject: RE: [Bldg-sim] Glass center-of-glass to assembly U-Value?

 

Can we use glass center of glass shading coefficient for the assembly ? If
not, is there any similar table for assembly shading coefficient
calculation? 

Thanks. 

 

Ming Zeng, PE, LEEDR Accredited Professional
Mechanical Engineer

Image removed by sender. LEO A DALY
730 Second Avenue South, Suite 1100, Minneapolis, MN 55402-2455
T 612.338.8741    F 612.338.4840    D 612.341.9539    
 <http://www.leoadaly.com> www.leoadaly.com     <mailto:MZeng at leoadaly.com>
MZeng at leoadaly.com


Image removed by sender. http://mail.leoadaly.com/greentree.gifPlease
consider the environment before printing.

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Andrew Craig
Sent: Monday, September 22, 2008 11:41 AM
To: Josh Greenfield; bldg-sim at lists.onebuilding.org;
equest-users at lists.onebuilding.org
Subject: Re: [Bldg-sim] Glass center-of-glass to assembly U-Value?

 

Attached is a handy spreadsheet from the Oregon Energy Code User's Manual.
Hopefully this is what you are looking for.

 

Regards,

 

Please note my new e-mail address: andrewc at interfaceeng.com

Andrew Craig, EIT,LEED AP/ Mechanical Designer/ Energy Analyst
INTERFACE ENGINEERING 
direct 503.382.2696 

  _____  

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Josh Greenfield
Sent: Monday, September 22, 2008 9:07 AM
To: bldg-sim at lists.onebuilding.org; equest-users at lists.onebuilding.org
Subject: [Bldg-sim] Glass center-of-glass to assembly U-Value?

 

Does anyone have any rules of thumb on a quick/easy approximation for taking
a Center-of-Glass U-value and converting it to an Assembly U-value based on
industry standard assembly constructions?  I know this depends on a lot of
variables, like frame material and conductance, and the size of the overall
glass assembly, etc., but I'm just looking for a quick estimate on
performance reduction for comparisons to other window types for a particular
building.

 

Also, is there an ASHRAE 90.1-2004 Baseline glass Visible Light
Transmittance (VLT)?

 

Josh Greenfield, PE, LEED AP
Senior Associate
Primera Engineers, Ltd.
100 S. Wacker Drive, Suite 700
Chicago, IL 60606
312.606.0910 Main
312.242.6392 Direct
312.606.0415 Fax
 <blocked::mailto:jgreenfield at primerachicago.com>
jgreenfield at primerachicago.com
 <http://www.primerachicago.com> http://www.primerachicago.com

Be Green...please consider the environment before printing this email.

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