[BLDG-SIM] glass u-vals

Leonard Sciarra leonard_sciarra at gensler.com
Wed Apr 18 07:07:23 PDT 2007


also see the envelope section of the 90.1 users manual, there they talk
about the difference between center of glass and frame, etc...
 

Leonard Sciarra, AIA, LEED ap

312.577.6580 (Dir)

G E N S L E R | Architecture & Design Worldwide

30 West Monroe Street

Chicago IL, 60603

312.456.0123

leonard_sciarra at gensler.com 

 

________________________________

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Annalisa
Simonella
Sent: Wednesday, April 18, 2007 3:37 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] glass u-vals



Hi Aaron,

The overall U-value is usually significantly higher than the centre-pane
U-value. In order to estimate the overall U-value of curtain walls or
windows you need to include the frames U-values and the edge effects and
the additional effect of point thermal bridges if present (structural
connections through the facade or window).

 

You may find some guidance in the NFRC standards
http://www.nfrc.org/technicaldocs.aspx  and you may use the software
THERM (downloadable from the LBNL website
http://windows.lbl.gov/software/ ) to calculate the U-value + edge
effects of frames. 

You may also find some guidance in the EN ISO 10077-1 and EN ISO 10077-2
which define a different method from the NFRC one, also the first one
gives simplified method and includes a table with pre-calculated linear
thermal transmittances (edge effect).

 

I hope it helps.

Best regards,

Annalisa.

 

Annalisa Simonella 

ArupFacadeEngineering 
13 Fitzroy Street 
London W1T 4BQ 

T +44 (0)207 75 54593 
F +44 (0)207 75 53626 
M +44 (0)77 1781 4793 

mailto:annalisa.simonella at arup.com 
http://www.arup.com/facadeengineering/ 

________________________________

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of
Dahlstrom, Aaron
Sent: 18 April 2007 04:24
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] glass u-vals

 

ASHRAE 90.1 window U-vals are for the "assembly."

Manufacturer's data for my project is for "center of glass."

 

Is anyone familiar with a way to get from one to the other?

 

I have a frame type and u-value; however, Fund. Chap 31 seems to caution
against doing hand calcs due to edge-of-glass effects.

 

Thanks,

 

Aaron Dahlstrom

AKF Engineers, LLP
1500 Walnut Street, Suite 1400
Philadelphia, PA 19102 
Phone:   (215) 282-2169
Fax:        (215) 735-6706
www.akf-engineers.com <http://www.akf-engineers.com/> 

 

 
 
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