[BLDG-SIM] ASHRAE 90.1 - window SHGC

[Leonard Sciarra]

Charlie,
 
(this maybe off topic) 
 
Good point, however, you must remember, that the development of the
prescriptive tables in 90.1 is based on a generic office building with
an floor plan aspect ratio of 1:1.  it is an internally load dominated
building, so even up to climate zone 7 (maybe not 8) in calculating
ANNUAL energy consumption, reducing solar heat gain (while allowing some
light in for assumed daylighting) was the key factor in the glazing
selection that comes out of the model.  Again, it was annual energy
consumption.  
 
Prescriptive codes are blunt instruments of change.   I think we all
agree that if you change the building aspect ratio, choose good
glass/shading and install a daylight harvesting/dimming system, design
the interior to take advantage of all of this, you are 70% of the way to
a kick ass energy efficient design.
 
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

 

________________________________

From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of D.
Charlie Curcija
Sent: Monday, April 09, 2007 8:50 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] ASHRAE 90.1 - window SHGC


International Glazing Database (IGDB), which is part of WINDOW 5.2
program (windows.lbl.gov) contains several hundred individual glass
layers whose solar transmittance is at or below 0.3, which, as a part of
glazing system and whole fenestration product, would produce SHGC of
0.25 or lower, which meets ASHRAE 90.1 for all climate zones.  The best
choice for low SHGC windows is so called spectrally selective low-e, and
there are at least 100 glass products with this type of low-e coating.
The cost of these products is only marginally higher than the cost of
clear glass.
 
I think that you are definitely overlooking something.
 
Having said that, I do want to state that the use of low SHGC products
in heating dominated climates (anything at or above climate zone 5) is
wrong and is the major flaw of both ASHRAE 90.1 and IECC 2006,
particularly for orientations with potentially high solar gain in the
winter, such as South orientation.
 
D. Charlie Curcija
Carli, Inc.
18 Tanglewood Rd.
Amherst, MA 01002
 
Tel: (413) 256-4647
Fax: (413) 256-4823
cell: (413) 575-3487
email: curcija at fenestration.com
<blocked::mailto:curcija at fenestration.com> 
web: http://www.fenestration.com <http://www.fenestration.com/> 
 
Support open document format as the best way to assure full
compatibility and interoperability! 
 


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