[Bldg-sim] ASHRAE 90.1 and Vacancy Sensors

[West, Scott P]

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 <mailto:scott.west at jacobs.com> | www.jacobs.com<http://www.jacobs.com/> | www.jacobs.com/energyportfolio<http://www.jacobs.com/energyportfolio>


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