# [Bldg-sim] Calculating the exterior lighting power allowance for LEED 2009

Nicholas Caton ncaton at catonenergy.com
Fri Mar 20 15:12:53 PDT 2015

```Happy Friday!

You count surfaces which are illuminated by fixtures on-site.  If a walkway
or potion thereof is *not* illuminated, you don’t count it for allowable
watts.

If more than one surface type is illuminated by a single fixture, I count
both towards the allowable total.  For both of the examples you provided, I
would count the length of linear walkway you (or more specifically the
guy/gal responsible for the lighting design, if it isn’t you) can back-up
as being “sufficiently illuminated.”

If it makes you feel better on the algebra side, I suppose you could
appropriate input wattage for a single fixture type between the
2+illuminated surfaces based on the relative area, but you aren’t getting a
different result that way.

I do not doubt there is an AHJ somewhere who feels differently on the
matter for compliance matters, but so far in my career I haven’t
encountered one.  Never had an issue on this point with LEED either –
that’s anecdotal and not a GBCI position statement… just my experience ;).

~Nick

*NICK CATON, P.E.*
*Owner*

*Caton Energy Consulting*
1150 N. 192nd St., #4-202

Shoreline, WA 98133
office:  785.410.3317

www.catonenergy.com

*From:* Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf
Of *Jones, Christopher
*Sent:* Friday, March 20, 2015 1:30 PM
*To:* bldg-sim at lists.onebuilding.org
*Subject:* [Bldg-sim] Calculating the exterior lighting power allowance for
LEED 2009

This is more of a LEED question but the task has fallen onto the shoulders
of the simulator.

I am trying to determine what areas should be included in the exterior
lighting power allowance calculation.

For example, the project site plan clearly shows walkways and parking
areas.  There are no specific exterior lights for the walkways, the parking
area light poles also light the walkways.  My assumption is that the
walkways should not be included in the calculation of the exterior lighting
power allowance.  Is this assumption correct?

Another example.  A light over an exit door, with no canopy, also lights
the walkway outside the door.  I assume that the this walkway should not be
included in the calculation?  It seems to me that also including the
walkway and setting the proposed lighting power to 0 Watts would be ‘double
counting’ against the baseline exterior lighting power allowance?

*Christopher Jones**,* P.Eng.
Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527

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