[BLDG-SIM] App G 2004 question
Bill Talbert
btalbert at aeieng.com
Wed Apr 18 08:53:33 PDT 2007
My experience has been that there are a reasonable number of buildings
that could benefit from optimizing orientation/geometry/fenestration
area, and ASHRAE/LEED's efforts to credit projects for doing this when
possible seems fair. I do agree however, that the rotation effort
doesn't always make sense as some projects can't realistically do
anything about orientation.
I haven't seen a need to complete additional calculations on the
baseline outside the software as the orientation/fenestration changes
can be done within the software most of the time. Simply rotating the
building isn't the best comparison as it does affect system sizes and
zone loads, but since App. G/LEED doesn't require reporting unmet load
hours for the incremental rotations, it doesn't appear that the intent
was to require detailed system and zone level adjustments for these
runs.
The question is whether creating an 'optional' path makes it easier for
projects to ignore orientation and not be penalized for an orientation
that results in higher energy consumption/costs. I would vote for
keeping it in and requiring the project team to document why orientation
is not a valid ECM for a specific project. This would require more
'interpretation' by the LEED reviewers, but makes the process more
flexible.
Bill Talbert, PE, LEED® AP
Mechanical Systems
Phone: (608) 441-6677
E-mail: btalbert at aeieng.com
Affiliated Engineers Inc.
5802 Research Park Blvd.
Madison, WI. 53719
Tel. (608) 238-2616
Fax. (608) 238-2614
>>> "Brandon Nichols" <BrandonN at Hargis.biz> 4/17/2007 6:44 PM >>>
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 ( http://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™ and CHPS. 20 years
experience includes thousands of buildings, and more than 35 projects
pursuing and achieving LEED™ 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 ( http://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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