[Bldg-sim] Appendix G - Base Case Orientations and Glazing

Fred Porter FPorter at archenergy.com
Mon Dec 1 13:36:24 PST 2008


Aha. Yes, there it is in the NC 2.2 revised EAc1 section, not under the
envelope heading of course. But if using the PRM from the 2007 App G, I
would reference the 2007 Users' Manual for further explanation and find
on G-16:
 
SHGC
"... The prescriptive standards give SHGC criteria
for all orientations and provide an
exception for north facing fenestration.
The exception is not used for the baseline
building; the criteria for all orientations are
used for all orientations. The maximum
SHGC is a function of the glazing
percentage, which is taken from the
proposed design or 40% of the gross
above-grade exterior wall, which ever is
less."
 
Which happens to be exactly the same text as in the 2004 UM. Of course,
if using 2007 App G, baseline models are supposed to reflect the more
stringent window parameters in Chapter 5.
 
Fred
 
 

>>> "James Hansen" <JHANSEN at ghtltd.com> 12/1/2008 8:10 AM >>>
Sorry, I should have read further before posting.  In the LEED-NC
reference guide, it states:

 
“The four Baseline Design energy models are identical to each other,
except that the building orientation for each model is modified as
described in ASHRAE Std 90.1 Table G3.5.1a, and the window SHGCs are
revised to reflect the minimum ASHRAE Building Envelope Requirements for
the revised building orientation.”
 
In other words, the USGBC, whether on purpose or not, has provided its
own exception to 90.1 that allows you to use the SHGC(north) in the
baseline models.  And yes, after rotating, you have to reassign the
proper SHGCs to the new “north”.
 

GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)

www.ghtltd.com ( http://www.ghtltd.com/ )
 

From:bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James
Hansen
Sent: Monday, December 01, 2008 10:01 AM
To: bldg-sim at lists.onebuilding.org 
Subject: Re: [Bldg-sim] Appendix G - Base Case Orientations and
Glazing

 
This is an interesting discussion (one that may have already occurred
previously).  According to the 90.1 User Manual:
 
“SHGC – The budget building design’s fenestration solar heat gain
coefficient is set to the maximum required for the climate.  The
prescriptive standards give SHGC criteria for all orientations and
provide an exception for north facing fenestration.  The exception is
not used for the baseline building; the criteria for all orientations
are used for all orientations…”
 
However, even the LEED-NC EAc1 template differentiates between the
North SHGC and the rest of the fenestration….if the exception is not to
be used, why would the USGBC have a place to enter the SHGC(north) for
the baseline building??  And why would they accept two different SHGCs
for the baseline building on the template?
 
I can’t seem to find any NC or CS CIRs that address this.
 
GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA  22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com ( http://www.ghtltd.com/ )
 
From:bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Ulrik
Welle-Strand Horn
Sent: Monday, December 01, 2008 9:42 AM
To: Paul Riemer
Cc: bldg-sim at lists.onebuilding.org 
Subject: Re: [Bldg-sim] Appendix G - Base Case Orientations and
Glazing

 
Paul, 

That's a VERY valid point. Thanks for pointing it out.


Ulrik Welle-Strand Horn 
Sustainability Engineer


Silpa Inc.
si m p l e  .  s c i e n t i f i c  .  s u s t a i n a b l e

AMERICAS | MIDDLE EAST | ASIA
www.silpainc.com ( http://www.silpainc.com/ )


India: +91.90080.96083

On Mon, Dec 1, 2008 at 7:51 PM, Paul Riemer <Paul.Riemer at dunhameng.com>
wrote:

I read Table G3.1 section 5 sub item (c) under the baseline building
performance column to require use of the "SHGC_all" for all vertical
glazing.  Have others read that and reached a different conclusion?  Did
I miss an addenda? or a CIR?
 

From:bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James V.
Dirkes II P.E.
Sent: Monday, December 01, 2008 8:09 AM
To: 'Ulrik Welle-Strand Horn'; bldg-sim at lists.onebuilding.org 
Subject: Re: [Bldg-sim] Appendix G - Base Case Orientations and
Glazing

 
Dear Ulrik,
 
Since the intent of the Standard is to assign the better glazing
performance to non-North walls, I always rotate the glazing
characteristics with the building. (e.g., I assign the "North" glazing
characteristics to the elevation that, after rotating, faces North)

 

The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
 

 

 

From:bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Ulrik
Welle-Strand Horn
Sent: Monday, December 01, 2008 7:30 AM
To: bldg-sim at lists.onebuilding.org 
Subject: [Bldg-sim] Appendix G - Base Case Orientations and Glazing
Dear all,

When you are rotating the building through 4 different orientations, do
you change the glazing so that the glazing with the highest SHGC is
always faces north, or do you put the glazing with high SHGC on the
original north facade, and then rotate the building so that the high
SHGC glazing faces the east, south and west orientations in subsequent
simulations?

Yours faithfully,


Ulrik Welle-Strand Horn 
Sustainability Engineer


Silpa Inc.
si m p l e  .  s c i e n t i f i c  .  s u s t a i n a b l e

AMERICAS | MIDDLE EAST | ASIA
www.silpainc.com (
http://console.mxlogic.com/redir/?1psKUPuX9JdZZWXPPxI05ihWSOxrBYdTdTdA3Q29uABiV2Hsbvg57OFeDlxV1KhW4E4u00CTHFK6QkQTAmbI3APrypI5-Aq83iScDE4iZ9aCBQQg22OTMgA7Cy096y0Kq81Dquq81bquq80N6nMDIVlxgQgr10Qg18_hik29KvxYY1NJ4SyrjvvuKYYYrV6r6
)


India: +91.90080.96083

 

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