[Bldg-sim] Low Ambient Strategy questioned in LEED Review
Bishop, Bill
wbishop at pathfinder-ea.com
Thu Nov 17 10:16:46 PST 2011
I'll play devil's advocate here.
If the reviewer's interpretation of the baseline model is correct, the
maximum LPD values have been entered for the baseline per Table 9.6.1
(or maybe Table 9.5.1). Additionally, 4.02 kW of lighting has been added
to both the baseline and proposed models to represent task lighting via
plug-in desk lamps. I agree with the reviewer that plug-in desk lamps
are not process loads as they don't meet any of the 9.2.2.3 exceptions.
Presumably, installed lighting fixtures provide 20 fc in the studio
spaces and students will turn on desk lamps to increase the light level
to something in the range of 50 fc +/-. Therefore, the proposed model
would be claiming savings unfairly if the desk lamp power is added to
the baseline in addition to the Table 9.6.1 values. I'm not aware of a
LEED or ASHRAE 90.1 requirement that a proposed design must have a
lighting design that "satisfies" IESNA lighting guidelines. My guess is
that the reviewer is mentioning IESNA levels to support the position
that the desk lamp power needs to be removed from the baseline model. I
assume the reference to 9.6.3(b) is a typo and should be 9.6.2(b).
My approach would be to do the following:
1.) Pester the lighting designer for their estimate of desk/task
lighting power sufficient to meet desired lighting levels.
2.) Use that value in the proposed model in place of the 4.02 kW of
process lighting.
3.) Create and apply a unique desk/task lighting schedule.
4.) Remove the 4.02 kW load from the baseline.
5.) Allot a portion of the baseline lighting allowance to desk/task
lighting (equal to the power calculated/assumed for the proposed design)
and assign it to the desk/task lighting schedule.
Alternatively, you could argue that your 4.02 kW value is reasonable and
leave it in the proposed model, but remove it from the baseline. The
worst alternative would be to follow the guidance in Appendix G Table
G3.1(6b) and "assume identical lighting power for the proposed and
baseline designs", since the architecture studios could be interpreted
to meet the exception of "other spaces in which lighting systems are
connected via receptacles and are not shown or provided for on building
plans".
It is also possible that I don't understand task-ambient lighting and
could use some education. ;)
Regards,
Bill
<mailto:wbishop at pathfinder-ea.com>
________________________________
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen
Walkerman
Sent: Thursday, November 17, 2011 12:38 PM
To: Carol Gardner
Cc: bldg-sim at lists.onebuilding.org; Tom Butler
Subject: Re: [Bldg-sim] Low Ambient Strategy questioned in LEED Review
Nick,
I mostly agree with your approach, however I disagree on one point -
even though desk lamps may be plugged-in and not permanently installed,
if they are part of the overall lighting plan, then I think that they
should be included in the proposed model and not in the baseline. If
you have low footcandles in a space, but for whatever reason, task
lighting is not required (this architectural studio uses giant
multi-touch computers for drawing), then task lights should be modeled
equally in both models.
--
Karen
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James
Hansen
Sent: Thursday, November 17, 2011 11:47 AM
To: Nick Caton; Carol Gardner; Tom Butler
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Low Ambient Strategy questioned in LEED Review
I suggest you contact GBCI thru:
http://www.gbci.org/contactcertification.aspx
I had an issue a few months ago where I believed the reviewer was
incorrect in their comment, and Gail Hampshire (Technical Director of
the HVAC/Energy team) was very helpful in resolving the issue and making
other reviewers aware of it. She said the above contact method is best
to make sure your question gets properly addressed for your project now,
and for future projects.
I agree with Nick - this review comment is at least partially incorrect,
in that you can't negate an ECM that the design engineer has implemented
just because the result may not comply with an IESNA "guideline". That
would be like saying that an improved exterior lighting design is not
allowed because the resulting footcandle levels don't comply with a
random GSA requirement, or something to that affect.
GHT Limited
James Hansen, P.E., LEED AP
Senior Associate
1010 N. Glebe Road, Suite 200
Arlington, VA 22201-4749
703-243-1200 (office)
703-338-5754 (cell)
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 Nick Caton
Sent: Thursday, November 17, 2011 11:40 AM
To: Carol Gardner; Tom Butler
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Low Ambient Strategy questioned in LEED Review
Tom et al:
To your reviewer's first paragraph... this is something of a tangent for
your quandary, but it sometimes infuriates me how many in our industry
try to apply/enforce/design around the recommended illuminance level
tables without reading the (short!) chapter discussing what they mean
and how they're intended to be used and not used. They are emphatically
NOT "minimums." I have been cornered on this a few times by select
individuals outside of a LEED review - suffice to say reviewers who
don't learn what they're enforcing run the risk of demonstrating their
incompetence.
It appears: (1) your reviewer does not understand task-ambient lighting
and could use some education in that dept and (2) you have not
communicated exactly what that 20fc figure means. Your reviewer has the
impression task surfaces will only have 20fc after all sources (which
would be bad lighting for an architecture studio). Correct that
impression, and further explain how the targeted illuminance values are
going to be achieved.
"Installed interior lighting power" is a 90.1 glossary term. For
90.1-2004/2007, it only includes "permanently installed" fixtures*.
Reviewer is having a quibble over vocabulary... If I'm not mistaken,
desk lamps are plug loads, and plug loads are process loads. Simple.
Perhaps different terminology is part of any revisions you may need to
make. I think the term "process lighting" is something your reviewer
may be making up, but he/she is referring to lighting integral to
refrigerator casework and such in that long list of exceptions... you
should not need to "exempt" desk lamps because they're not permanently
installed and so inherently are not part of "installed interior lighting
power" to begin with.
9.6.3(b) is for VDT's (computer screens) - sorta confusing reference...
Does anyone know if there is precedent for this? The function of this
passage as I understand it is to permit additional lighting beyond the
interior lighting power allowance under the space-by-space method... not
to limit task lighting within the allowance. Again, I think the term
"task-ambient" is throwing your reviewer off.
I have not attempted documenting this myself, but am not aware of
anything in 90.1 or the IESNA Handbook that disallows the use of
non-permanently installed lighting (however variable it may be in a
college setting) to achieve the targeted illuminance values. This may
warrant some investigation however to be sure.
~Nick
* I haven't reviewed 90.1-2010 thoroughly, but it appears revised in
this regard.
NICK CATON, P.E.
SENIOR ENGINEER
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com
From: bldg-sim-bounces at lists.onebuilding.org [
mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Carol
Gardner
Sent: Thursday, November 17, 2011 3:37 AM
To: Tom Butler
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Low Ambient Strategy questioned in LEED Review
tb,
After, you have read through this couple of times, or looked at it in
an Excel table, you will figure out the changes you have to make and
make them. Always remember, do the proposed case first and then back out
the baseline, which must meet the applicable code.
I think in a case like this building you would have had a different
result if you had attached, or put into the form, what you were trying
to do and how you did it. Your explanation is quite good and it gives
the reviewers something to look at besides numbers. Then you get to
exercise both sides of your brain.
Cheers,
Carol
On 11/16/2011 10:26 PM, Tom Butler wrote:
Sorry for the long attachment here, but this LEED v2.2 EAc1 comment has
me really confused so I want to post it in its entirety.
1. The EAc1 Narrative describes the interior lighting design target
for all studio spaces is 20 fc and that task lights have been modeled
identically in the Baseline and Proposed case. However, according to the
IESNA Lighting Handbook, ninth edition, the minimum horizontal design
illuminance for art studios is 50 fc and for reading areas with
handwritten tasks is 30 fc. The ASHRAE allowances represent the power
allowance required to meet the minimum IESNA illuminance requirements
for various space types. It is inappropriate to claim savings for
designs that do not meet the minimum lighting level requirements and
model the additional lighting power in the Baseline for lighting in the
Proposed that is required to perform the anticipated tasks.
Also, Table 1.4 reports that 4.02 kW of process lighting has been
modeled in both cases, and it is assumed that this represents the task
lighting. Process lighting is limited to the exempt interior lighting
applications described in Section 9.2.2.3. Task lighting is regulated
and thus not considered a process load. Section 9.6.3(b) does provide an
additional allowance for task lighting when the Space by Space Method is
used, but this may not be used for lighting required to raise the
ambient lighting to meet the required lighting levels. If this
additional allowance is used in the Proposed design, the Baseline must
be modeled with the same power as the Proposed up to the 0.35 W/square
foot allowance. Please remove all task lighting power from the Baseline
model that is required to meet the IESNA recommended illuminance levels.
If any of the additional allowance from Section 9.2.2.3 is applied to
the Baseline case, provide calculations verifying that this additional
lighting is not required in the Proposed case to meet the required
illuminance levels and confirming that this only represents the portion
of the additional allowance that is used in the Proposed case.
My first question; isn't low ambient-task specific a commonly accepted
energy use reduction strategy? Why would I model a lighting design in
the proposed solution which isn't installed and how would one determine,
without an extensive lighting design effort, the appropriate lighting
power to achieve 50fc, or 30fc? (not quite sure which one they want)
Second, the spaces in question are architecture college studios. If the
task lighting is a plug in desk lamp, provided by the student, then am I
correct in assuming it's not regulated by 9.2.2.3? I've assumed 60W per
lamp as plug load, but there no way that the lamp type or light
distribution can be controlled as defined in 9.6.3.b, nor is it a given
that a lamp will be used.
I'm at a loss as to how to respond to this.
Thanks for any input.
tb
Tom Butler
Residential Green Building Services Project Manager
Tel: 404-604-3635
Fax: 404-872-5009
Email: tbutler at southface.org <mailto:amcfarland at southface.org>
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