I'm working on a project and the owner selected a decorative post top fixture to line the drive into the site. The site is small enough where this fixture is the main site fixture. One look at it and I said it won't comply with SSc8. I was told to look at it and do what I can.
The fixture had 10% uplight. Then I was told it had a special glass optic to limit uplight. That knocked it down to 4% uplight. This is in an LZ2 location so I need a total site uplight of 2% or less.
I thought I'd try for Pilot Credit 7. I imported the IES file into Visual's photometric viewer to see it's BUG rating. It had a U3 rating. Tried the lowest wattage version of the fixture and it's still U3 rating.
I looked closer at the values and realized they already updated the software to TM-15-11. But PC7 is based on TM-15-07. The uplight values were reduced from 100 lumen in '07 down to 50 lumens in the '11 version. This low wattage version has 88 lumens in one of the uplight zones. So it is actually a U2 rating until LEED v2012 comes out.
Just found it odd that this fixture can be non compliant for SSc8 in both v2009 and v2012 but manages to comply with PC7.
Glenn Heinmiller
PrincipalLam Partners
100 thumbs up
November 3, 2011 - 10:46 pm
Bill,
Interesting observation. And I think I understand what you are saying. It brings up a few issues.
1. The MLO and TM-15-11 were just issued this summer with the U rating change right in the middle of the development of LEED-2102 and the final stages of IGCC. This caused quite a bit of consternation because previous versions had already been used for basis of LEED 2012 drafts, 189.1 and IGCC. It will all get sorted out eventually, but I'd expect some confusion over BUG ratings, because if you happen to be using old software that hasn't been updated for TM-15-11 you are going to get bogus results (or if the BUG tables in a particular standard haven't been updated but you are using TM-15-11 BUG ratings.)
2. LEED 2012 public draft #3 will be out soon (next few months?) and I'm assuming that PC7 will be updated to be this draft. So if you comply under PC7 now, I'd say you best get your submittals in :-)
I think you will like draft #3 of the credit - it has really been cleaned up a lot and is much clearer.
3. Do not expect the same stringency results under the "old" 2009 methods and the "new" BUG methods. There was never any intention for this. These methods were developed independently and at different times. The "old" method was developed for LEED by methods unknown to me, but the LZ concept and the idea of using vertical illuminances for trespass limits probably came from RP-33. The "new" BUG method came from the MLO development process. The idea was to add MLO/BUG methods to LEED in order to get consistency across standards and rating systems, and because BUG is will make compliance much simpler - no computer simulation required. It was decided to leave the "old" methods as an option, I think partly because BUG is new and untested, and partly to give designers another less prescriptive/more performance option for compliance and/or to stick with what they are familiar with. It will be interesting to see which options are chosen as PC7 and LEED-2012 start getting used. I predict that eventually the "old" methods will be dropped and LEED will follow the MLO as it develops.