[Bldg-sim] Low Ambient Strategy questioned in LEED Review

[Tom Butler]

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> 

Web: www.southface.org <http://www.southface.org/> 

241 Pine Street NE, Atlanta, GA 30308

 

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