All,
I've come across an interesting problem on a project. I'm modeling a building using App. G for LEED V3 submission (ASHRAE 90.1-2007 baseline). The building was actually designed to comply with most provisions of 90.1-2013 however. Most of our spaces employ "vacancy" sensors (automatic off after 30 min, manual on control) rather that occupancy sensors (automatic off after 30 min, automatic on control) for lighting control. As many of you are probably aware, 90.1-2007 App. G allows us to take a 10% savings (Table G3.2) on the LPD (it's well over 5,000 ft2). 90.1-2010 App. G allows the same reductions in lighting power but 2013 leaves it out since it's now required by the standard in most instances.
My understanding from SSPC 90.1 proceedings is that the committee determined that vacancy sensors save more energy than occupancy sensors (as they reduce false ons from transient movement). I'm not sure how these savings are being estimated because predicting occupancy patterns is always fraught with assumptions. Anyway, does anyone know if there is any guidance on claiming more than the standard 10% for occupancy sensors with these type of controls? I'd like to avoid performing an exceptional calculation measure if possible so any 90.1 or LEED Interpretations would be really useful.
Thanks,
Scott P. West, P.E., LEED AP BD+C, BEAP, BEMP | JACOBS | Mechanical Engineer | Energy & Power Solutions | 817.222.8512 office | 817.897.1882 cell | scott.west at jacobs.com
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I did some research on this topic a few years back, as our local utility
was interested in providing a higher level of rebates for vacancy sensors.
I found a white paper that showed the Title 24 research into this topic.
It showed an 11% increase (on average) in savings for vacancy sensors vs
standard occupancy sensors. I will have to see if I can dig the paper up,
though you might find it with a little googling. Anyways, that +11% is is
now written into our utility's modeling protocol for energy savings
calculations.
If you can find a white paper dated within 5 years, you can use it as the
basis for an Exceptional Calculation, but you will also have to show that
using vacancy sensors is NOT the design standard in your area. (If it's in
your local code, it won't fly with LEED.)
Good luck!
Elizabeth
*Elizabeth Gillmor PE, LC, LEED AP*
*e n e r g e t i c s **consulting engineers, llc*
energetics-eng.com
c 303.619.0091
Try this report from Southern California Edison:
http://www.etcc-ca.com/sites/default/files/OLD/images/stories/office20of20future20phase20ii20final202-15-091.pdf
Unfortunately it?s more than 5 years old, but hopefully it?s still useful for you.
Keith Swartz, PE
Senior Energy Engineer | Seventhwave | Madison.Chicago.Minneapolis
(formerly Energy Center of Wisconsin)
608.210.7123 | www.seventhwave.org