[bldg-sim] High Performance Glazing

[Mitchell Dec]

When using a "high performance glazing" you need to be careful.  Every
building has a different signature (i.e. different shape, size, occupancy,
climate, etc.)  Therefore, one should be careful to say a "high performance"
glazing is better than a lesser performance glazing.  It is best to model a
wide range of u-values such that you can see which glazing is optimal for
the specific building.  Often, one will see that a manufacturer says it is
"high performance" which it is on its own.  But, couple that with your wall
insulation and the "high performance" wall configuration requires a
different u-value.
 
You will see a point of diminishing return and in many cases a point at
which the lower window u-value coupled with your wall insulation will in
fact cause one load to go up and the other to go down or vice versa,
depending on your climate.  This is also similar in determining when you
have too much or too little insulation.  What "high performance" glazings do
is allow an opportunity to determine what the most cost effective path is,
decreased window u-value or increased wall insulation.  Therefore, one is
able to have several optimization paths.
 
I find it convenient to produce a graphical representation (excel is pretty
easy for this) to graph the variable versus the desired output (energy used
or dollars saved, if a LEED project).
 
I hope this helps.
 
-Mitch
 

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Mitchell J. Dec
Energy Analyst 
503.345.6283 | mdec at glumac.com <mailto:mdec at glumac.com>  

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

  _____  

320 SW Washington, Suite 200
Portland, OR 97204-2640
T.  503.227.5280  F. 503.274.7674

Thinking. Inside the building.
http://www.glumac.com/ <http://www.glumac.com/>  

-----Original Message-----
From: Zoeteman, Mark R. [mailto:mrzoeteman at FTCH.com]
Sent: Thursday, December 15, 2005 12:53 PM
To: bldg-sim at gard.com
Subject: [bldg-sim] High Performance Glazing



I am modeling high performance glazing with U=0.14, SC=0.35 and comparing to
typical 1" thick insulating low-e glass with U=0.33, SC=0.76.  Climate is
midwest US and 86% of the glass is facing north. The north wall is basically
all glass and spandrel. Heating is suppied from district steam supply.

Results show increased steam energy consumption from February through
September with high performance glazing and less for remaining winter
months. HVAC system is VAV with hot water reheat coils.

Overall annual steam energy consumption reduction is very small. I expected
to see significant heating energy savings due to increased perimeter
R-value. Has anyone modeled high performance glazing and seen similar
results? 


Mark Zoeteman 
FTC&H, Inc. 
(616) 464-3739 
mrzoeteman at ftch.com 




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