Hi all,
Mid-design, the building owner has decided to implement the Lutron Quantum system. This is the plan:
Over 95 percent of light fixtures in the building will be individually addressable and dimmable. Every space with a window will have daylighting control. Every space will have occupancy sensors.
At the owner's request, the electrical engineer has laid out light fixtures to improve the normal variances in illumination within a space. The execution specifications state that every space will be tuned by dimming prior to occupancy, to achieve the design footcandle level for that space.
The operating sequence is also impressive. In large or long spaces like hallways, an occupant will be able to observe the lights brightening in front of him and dimming behind him as he walks.
I know that all the extra energy savings from this system would require a huge extraordinary calculation in post-processing, and that calculation would be dubious at best. I think there may be a pilot credit in the next version of LEED, but at this time we cannot take advantage of this extra auto-dimming savings for EAc1.
So here's my issue. Substantial extra lumens were designed into every space, both to provide more even illumination and to accomodate the fact that light fixtures are only made in discrete wattages. The engineer's spec calls for a permanent limit be set for all light fixtures on the system. The limit will be 80 percent light output. In other words, all future light operation will permit no more than 80 percent light output for any fixture, and it cannot be changed. The electrical engineer, architect, and building owner will certify this upper limit lockout.
The question is: May we multiply the fixture as-purchased input wattage by 0.8 when calculating the lighting watts per square foot in our proposed design model? If necessary, Lutron can assist with the security of this limit by setting it at the factory prior to shipping so that it cannot be accessed by anyone at the site. This certainly seems reasonable, but of course we are unsure if it will be accepted or I wouldn't be posting this.
Thank you so much,
Dave
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 12, 2012 - 2:46 pm
90.1 requires using the maximum lamp/ballast wattage, see 9.1.4b.
To claim less you would probably need to do an exceptional calculation and be able to prove that the lamp/ballast maximum wattage is fixed and cannot be adjusted.
A better idea might be to redesign the lighting to eliminate the excess illumination. Using controls to address overdesign seems kind of silly to me especially if it is still being designed. This could save first cost by eliminating unnecessary fixtures. So instead of reducing the wattage by 20% why not eliminate 20% of the fixtures! (I do realize that this is a simplification and good lighting design must account for issues like uniformity, etc., etc.).
Just because we can does not mean we should.
David Weigel, PE
Managing MemberThe Watt Doctors, LLC
16 thumbs up
October 12, 2012 - 3:38 pm
Thank you Marcus.
I thought it might be iffy. But the owner and designer both want to spend the extra money for aesthetic reasons. I will see what sort of proof they can offer before we incorporate this into the model...
Dave
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 12, 2012 - 3:52 pm
I suppose it is their money to waste but it does seem to be the opposite of designing a green building to me.
Steven Er
11 thumbs up
October 16, 2012 - 9:57 pm
Hi,
CIR 2417 dated 2/3/2009 stated the similar condition here. The approach that limiting the lighting power seems to be accepted. Any idea this ruling is still applicable?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
October 17, 2012 - 9:53 am
Thanks for pointing out the Interpretation Steve. It directly contradicts 9.4.1b and I am not sure that when it was written that was taken into account. Counting the reduced LPD for the CI prerequisite also may not be the same thing as claiming energy savings in NC EAc1.
I'll bring up the issue with USGBC/GBCI.