[BLDG-SIM] App G 2004 question
Brandon Nichols
BrandonN at Hargis.biz
Tue Apr 17 16:44:27 PDT 2007
Thanks Bill & Bing for your replies,
Previously I started this topic going again with a point-by-point
description of some implementation problems caused by the 'orientation
averaging' and 'fenestration leveling' requirements of LEED 2.2 /
90.1-2004 Appendix G; please refer to that post for further details.
Here let me try to be as clear and concise as possible:
* There are, perhaps, only 10% of all buildings that can take advantage
of alternate orientations. Most are site-constrained, or have already
been built.
* There are perhaps a greater fraction than 10% of all buildings that
can take advantage of alternate glass distributions, however glass
distribution is also often constrained by site considerations.
* So to accommodate a minority of cases, LEED 2.2 / 90.1-2004 Appendix G
seems to impose a significant and relatively meaningless calculation
burden on the majority, by requiring the development of a fictitious
baseline that needs to be manually maintained outside of the simulation
software.
* How can we waive these requirements in LEED 2.2 for projects that
cannot realistically benefit from them, and substitute a "code minimum"
baseline oriented identically and glazed similarly to the proposed
building?
On the last point, even if a site-constrained project could
'theoretically' benefit from orientation averaging or fenestration
leveling, in principle I believe LEED teams should have the option to
forgo that marginal benefit the sake of the simplicity, clarity,
accuracy, and meaningfulness of the comparative calculations.
Thanks for your time, and hard work on LEED...
Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS
600 Stewart St
Suite 1000
Seattle, WA 98101
d | 206.436.0400 c | 206.228.8707
o | 206.448.3376 f | 206.448.4450
www.hargis.biz
_____
From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of William
Bahnfleth
Sent: Tuesday, April 17, 2007 2:48 PM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] App G 2004 question
One of the perceived shortcomings of Ch. 11 as a method for computing
energy savings for green building rating purposes was that it did not
provide sufficient opportunity to take credit for energy savings through
envelope design and building orientation on the site. The cited portion
of Ch. 11 (Table 11.3, item 5) requires all envelope components of the
Budget Building to be the same as the Proposed Building, eliminating
that opportunity.
The parallel part of Appendix G relaxes this constraint in a way that
should make it possible for the Proposed Building to show a greater
reduction in energy cost. This is done by removing self-shading,
distributing fenestration uniformly instead of optimally, and by
averaging the effects of orientation. If someone has done a robust test
of orientation averaging vs. best and worst case orientations that shows
negligible scatter around the mean, I am sure the ECB Subcommittee would
be interested to see it.
The distribution of glazing was made uniform mainly because of the
intent to average multiple orientations.
Bill Bahnfleth
At 04:47 PM 4/17/2007, Charles Christenson wrote:
As clarification, LEED v2.2 requires the use of the Performance
Rating Method from Appendix G, not the ECB method (which was used in
previous versions of LEED). In fact, in the Reference Guide section of
LEED v2.2 titled "Common mistakes made using the Performance Rating
Method", the first mistake listed is "The Energy Cost Budget Method
(Section 11) is incorrectly used rather than the Performance Rating
Method (Appendix G) to obtain EA Credit 1 credit".
Brandon - when I first read Appendix G, I was puzzled by their
motivation. Why rotate the building if you are already evenly
distributing glass? I am still not sure what the justification from
ASHRAE is on that one. I have not seen anything from USGBC that gives
any exceptions to the rotating requirement.
Charlie Christenson, LEED AP
Brummitt Energy Associates, Inc.
2171 India Street, Suite B
San Diego, CA 92101
tel: 619-531-1126
fax: 619-531-1101
cchristenson at brummitt.com
www.brummitt.com <http://www.brummitt.com/>
A net-zero carbon company, using www.b-e-f.org/GreenTags
Brummitt Energy Associates, Inc. helps you achieve comfortable,
highly energy efficient, cost-effective projects by integrating the
building design with daylighting, electric lighting, and mechanical
systems. Consulting from early design through construction
documentation, we specialize in energy and daylight modeling, increasing
financial incentives, and documentation for Title 24, LEED(tm) and CHPS.
20 years experience includes thousands of buildings, and more than 35
projects pursuing and achieving LEED(tm) ratings, from Certified to
Platinum.
From: BLDG-SIM at gard.com [ mailto:BLDG-SIM at gard.com
<mailto:BLDG-SIM at gard.com> ] On Behalf Of Leader, Philip
Sent: Tuesday, April 17, 2007 1:02 PM
To: BLDG-SIM at gard.com
Cc: Shawn Gavras
Subject: [BLDG-SIM] App G 2004 question
The Appendix G is an informative appendix and is not part of
Standard 90.1. It is merely informative and does not contain
requirements necessary for conformance to the Standard.
In the Energy Cost Budget Method section in Table 11.3 under
Section 5 Building Envelope, it describes the requirements for the
Proposed Building design and the Budget Building design. The first
paragraph under the Budget Building design states.... The budget
building shall have identical conditioned floor area and identical
exterior dimensions and orientations as the proposed design, except as
noted in (a), (b), and (c) in this clause.
There's nothing in the Standard stating you must rotate the
building in 90 degree increments and average the results. We've never
been asked to do it to my knowledge by the USGBC during a LEED review of
our projects.
Philip S. Leader, PE
Director of Mechanical Engineering
Albert Kahn Associates, Inc.
7430 Second Ave.
Detroit, Michigan 48202-2798
Phone: 313-202-7834
FAX: 3130202-7334
Email: philip.leader at akahn.com
Website: www.albertkahn.com <http://www.albertkahn.com/>
_____
From: BLDG-SIM at gard.com [ mailto:BLDG-SIM at gard.com
<mailto:BLDG-SIM at gard.com> ] On Behalf Of Brandon Nichols
Sent: Tuesday, April 17, 2007 3:12 PM
To: BLDG-SIM at gard.com
Cc: Shawn Gavras
Subject: [BLDG-SIM] App G 2004 question
All,
This is an old thread, but one I thought worth revisiting to see
if there have been any developments. Specifically we are preparing a
LEED Silver project for submittal, and while we understand he intent of
the Appendix G 'multiple-orientation' and 'fenestration-leveling'
requirements, our evaluation is that they impose extensive calculation
requirements for arguably marginal returns on accuracy.
In the case of our specific building (as I would suspect the
case of 90%+ of all buildings) there's simply no latitude to change the
orientation. Similarly with glass distribution, the lobby and entryway
have the flexibility to be on one side and one side only of the
building, and thus distributing the glass equally amongst all facets for
the baseline model seems to add an unnecessary level of abstraction to
the comparative analyses.
Does imposing the requirement for analysts to spend considerable
effort developing fictitious baselines based on building orientations
and glass distributions that have 0% chance of construction seem to be a
reasonable requisite for LEED project certifications? What I mean by
'considerable effort' is:
* That the all baseline numbers for each of the four
orientations would need to be extracted from the analysis software,
averaged on a spreadsheet, and a similar extraction done for all
subsequent energy efficiency measure (EEM) comparisons. Posting these
numbers from analysis software to spreadsheets would be both
time-consuming and introduce another level of potential error, and thus
require additional error-checking.
* That a new building would need to be developed, with glass
redistributed equally amongst all facets, for the four-point orientation
exercise described above. Again, while this may sound reasonable from a
theoretical standpoint, practically speaking this requirement serves to
decouple the baseline from glazing-dependent energy efficiency measures.
How meaningful is changing the U-value or shading coefficient of the
glass in an EEM in comparison to a fictitious baseline, when the glass
distribution is crucial to determining whether or not the measure is
cost-effective? As with building orientations, posting these numbers
from analysis software to spreadsheets would be both time-consuming and
additionally error-prone.
All to fulfill the requirement of deriving a fictitious baseline
for use in the comparative analyses -- no doubt these requirements were
incorporated with good intention, but practical implementation
considerations seem to have not been considered carefully enough.
Further, we find the concept of comparing proposed energy
efficiency measures to a "code minimum" baseline building, oriented
identically and glazed similarly to each of the EEMs, to be intuitively
more meaningful to both the owner and project team (and thus presumably
to the LEED reviewer) than comparison to a fictitious baseline. This
approach allows the baseline to reside in the analysis software, and EEM
comparisons accomplished using the built-in 'parametric run' features of
the analysis software (eQuest and others) to reduce the time-consuming
error-prone tediousness of extracting and posting numbers to a
spreadsheet for comparative evaluation.
Has anyone had success in obtaining LEED project approval when
excepting these 'building orientation averaging' and 'glazing-area
leveling' requirements? What is required in terms of the LEED
application to waive these requirements?
Also, does anyone know if these requirements have been
identified for relaxation or revision in the next LEED update?
Regards
Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS
600 Stewart St
Suite 1000
Seattle, WA 98101
d | 206.436.0400 c | 206.228.8707
o | 206.448.3376 f | 206.448.4450
www.hargis.biz
_________________________________________________
At 08:41 AM 1/24/2006, Bill Bahnfleth wrote:
Modeling the building in the specified orientations and
averaging gives an orientation-neutral baseline.
Appendix G has been developed with substantial input from
experts at PNNL and after discussions with USGBC. Glad to hear that
modelers are ignoring whatever they don't understand or find
inconvenient.
Bill Bahnfleth
Member, ECB Subcommittee
At 09:42 PM 1/23/2006, Peter Alspach wrote:
A bit of a throw-back to the old 1989 version
then?
-----Original
Message-----
From: Kevin Warren
[
mailto:kevin at warren-energy.com
<mailto:kevin at warren-energy.com> ]
Sent: Monday, January 23, 2006 5:46
PM
To: peter.alspach at arup.com;
bldg-sim at gard.com
Subject: RE: [bldg-sim] App G 2004
question
Peter,
I believe the intent is to give you a way to get some
savings
from
orienting your building with an eye toward savings. If
you pay
attention
to the sun in your design (passive solar and/or
daylighting),
you should
get some savings relative to the average of the rotated
orientations.
Similarly, you could get a penalty if you have too much
west-facing
glass.
I'm not sure how strictly this provision is being
enforced. Most
of the
modelers I have spoken to ignore it, but that is a very
unscientific
sample.
These modelers may not be submitting to
USGBC.
For a utility incentive program, it often does not make
sense to
do this
rotation. Those incentive programs typically care about
the
savings from
incremental changes to the design, particularly those
changes
that carry
an incremental cost. I'm not sure how one would
determine an
incremental
cost for your building's orientation, so it is not a
factor that
would
typically be
eligible.
Kevin Warren, P.E., CEM, LEED
AP
Warren Energy Engineering,
LLC
(610) 255-3798
ph
(610) 255-3406
f
-----Original
Message-----
From: bldg-sim at gard.com
[mailto:bldg-sim at gard.com]On
<mailto:bldg-sim at gard.com%5DOn>
Behalf Of Peter
Alspach
Sent: Monday, January 23, 2006 8:04
PM
To:
bldg-sim at gard.com
Subject: [bldg-sim] App G 2004
question
Anyone out there know the source of why one would be
required
to
simulate a building in an orientation that it is not in?
This
doesn't
really make any sense to me - am I missing
something?
Peter
-----Original
Message-----
From: bldg-sim at gard.com
[mailto:bldg-sim at gard.com] On
Behalf Of Rohini
Brahme
Sent: Monday, January 23, 2006 1:13
PM
To:
bldg-sim at gard.com
Subject: [bldg-sim] App G 2004
question
I have a question about the Appendix G in 90.1,
2004.
In Table G3.1 the baseline building is to be simulated
as
follows:
" Orientation. The baseline building performance shall
be
generated by
simulating the building with its actual orientation and
again
after
rotating the entire building 90, 180, 270 degrees, then
averaging the
results. The building shall be modeled so that it does
not
shade
itself."
What does --- the building shall be modeled so that it
does not
shade
itself ----
mean?
Does it mean that if there is, for example, an L shaped
building
(which
self shades), it has to be modeled as square?
rectangle?
Any thoughts on this
appreciated.
Thanks
- Rohini
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_________________________________________________
William P. Bahnfleth, PhD, PE, Fellow ASHRAE
Professor of Architectural Engineering
Director, Indoor Environment Center
The Pennsylvania State University
104 Engineering Unit A
University Park, PA 16802 USA
voice: 814.863.2076 / fax: 814.863.4789
e-mail: wbahnfleth at psu.edu
www.arche.psu.edu/faculty/WBahnfleth/
http://www.engr.psu.edu/ae/iec/
_________________________________________________
Brandon Nichols, PE
Mechanical
HARGIS ENGINEERS
600 Stewart Street
Suite 1000
Seattle, WA 98101
www.hargis.biz <http://www.hargis.biz/>
d | 206.436.0400 c | 206.228.8707
o | 206.448.3376 f | 206.448.4450
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_________________________________________________
William P. Bahnfleth, PhD, PE, FASHRAE
Professor of Architectural Engineering
Director, Indoor Environment Center
The Pennsylvania State University
104 Engineering Unit A
University Park, PA 16802 USA
voice: 814.863.2076 / fax: 814.863.4789
e-mail: wbahnfleth at psu.edu
www.arche.psu.edu/faculty/WBahnfleth/
http://www.engr.psu.edu/ae/iec/
_________________________________________________
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