[Bldg-sim] Low Ambient Strategy questioned in LEED Review
Christopher Schaffner
chris at greenengineer.com
Thu Nov 17 12:06:51 PST 2011
Here's the logic in 90.1 Appendix G:
1. In 90.1 Appendix G, all lighting, including "task and furniture mounted
fixtures" must be included in the proposed case. (Table G3.1.6.d).
2. Table G3.1.6.b says that lighting power shall be determined in accordance
with Sections 9.1.3 and 9.1.4.
3. Section 9.1.3 says that all lighting power must be included "except as
specifically exempted in 9.2.2.3."
3. In 90.1 there is no such thing as "process lighting". If the lighting
doesn't meet one of the exceptions in 9.2.2.3 it must be included in the
model.
4. Note that 9.2.2.3.p applies, so furniture mounted task lighting with
automatic shutoff complying with 9.4.1.4(d) does NOT need to be included in
the model, provide it can be shown that it is "in addition to the general
lighting"
I think the reviewer basically pointing out your circular logic. You've
argued that 20fc is adequate, but then argued that additional lighting
shouldn't be counted against you, because you need more light.
--
Chris Schaffner, PE
LEED Fellow
Founder and Principal
The Green Engineer, LLP
Sustainable Design Consulting
50 Beharrell Street
Concord, MA 01742
T: 978.369.8978
M:978.844.1464
chris at greenengineer.com
www.greenengineer.com
The Green Engineer, LLP is a Certified B Corporation
From: "Bishop, Bill" <wbishop at pathfinder-ea.com>
Date: Thu, 17 Nov 2011 13:16:46 -0500
To: James Hansen <JHANSEN at ghtltd.com>, Nick Caton
<ncaton at smithboucher.com>, Carol Gardner <gems at spiritone.com>, Tom Butler
<tbutler at southface.org>
Cc: <bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] Low Ambient Strategy questioned in LEED Review
I¹ll play devil¹s advocate here.
If the reviewer¹s 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 don¹t 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. I¹m not aware of a LEED or ASHRAE 90.1 requirement that
a proposed design must have a lighting design that ³satisfies² 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
³assume identical lighting power for the proposed and baseline designs²,
since the architecture studios could be interpreted to meet the exception of
³other spaces in which lighting systems are connected via receptacles and
are not shown or provided for on building plans².
It is also possible that I don¹t 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 reviewer¹s first paragraphŠ 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 they¹re
intended to be used and not used. They are emphatically NOT ³minimums.² I
have been cornered on this a few times by select individuals outside of a
LEED review suffice to say reviewers who don¹t learn what they¹re
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.
³Installed interior lighting power² is a 90.1 glossary term. For
90.1-2004/2007, it only includes ³permanently installed² fixtures*.
Reviewer is having a quibble over vocabulary... If I¹m 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 ³process lighting² 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 exceptionsŠ you should not need to ³exempt²
desk lamps because they¹re not permanently installed and so inherently are
not part of ³installed interior lighting power² to begin with.
9.6.3(b) is for VDT¹s (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 methodŠ not to limit task
lighting within the allowance. Again, I think the term ³task-ambient² 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 haven¹t 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 <http://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; isn¹t low ambient-task specific a commonly accepted
energy use reduction strategy? Why would I model a lighting design in the
proposed solution which isn¹t 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 it¹s not regulated by 9.2.2.3? I¹ve 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.
I¹m 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>
Web: www.southface.org <http://www.southface.org/>
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