I'm working on a project that totals approximately 178,000 sf, of which approximately 140,000 sf is office space (3 stories tall), with the other 38,000 sf being conditioned manufacturing space. In determining what the baseline systems are, I'm not sure which square footages I should use. Under the exceptions of G3.1.1, the manufacturing area should have a baseline HVAC system of Type 3 or 4. If the gross square footage of the entire building is used (which is over the 150,000 sf threshold), that would make the baseline HVAC system for the predominant office occupancy be Type 7 or 8. But, since the manufacturing area is broken off onto its own HVAC system type, shouldn't the predominant office occupancy be judged on the 140,000 sf that it takes up, rather than the total building gross square footage, and thus have a baseline HVAC system of Type 5 or 6?
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
July 11, 2012 - 6:46 pm
I think this is debatable. It is our opinion that the total square footage should determine the HVAC system type for the baseline and then the exception is applied to the applicable space. Applying the exception does not lower the total square footage. So I would say a 7 or 8.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
July 13, 2012 - 11:53 am
I checked into this further and apparently the debate is over. While I still believe that our opinion above makes the most sense, apparently GBCI has decided otherwise. So the square footage to which an exception is applied is subtracted from the total and then the remaining square footage is used when entering Table G3.1.1A.
Josh Greenfield
Director of High Performance DesignHDR
November 19, 2018 - 10:33 am
Marcus...do you happen to have the website location of the full interpretation text from GBCI that you referenced as I can’t seem to find it. I totally understand if you can’t recall as it was 6 years ago!
Additionally, thoughts on if the # of floors would also decrease? Example: I have a 154,000 7-story building but 2 full floors fall under the exception B, therefore can I “enter” table G3.1.1A with a 110,000 5-floor remainder to determine baseline system in lieu of the 7 floors (this would result in a system type 5 versus 7). Let me know your thoughts and if you can find the GBCI text. Thanks.
David Eldridge
Energy Efficiency NinjaGrumman/Butkus Associates
67 thumbs up
November 20, 2018 - 12:50 pm
Consistency-wise I think your approach makes sense Josh, that the floors should also be exempted.
Can you also check the 90.1 User's Manual? I don't recall right off-hand, but perhaps an example has been added since that time to clarify the intent of the system selection algorithm. The question obviously has come up a few times.
I can see Marcus' approach making sense where the exempted areas are relatively small. If we envision a building that is on the edge of the total area threshold and has a 60/40 split it would be less intuitive that the predominant 60% should have the total area/floors and not the net of area/floors after the exemption.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
November 20, 2018 - 1:35 pm
I do not think this was ever codified in a LEED interpretation. This was decided by GBCI internally and I am not aware of it being made public except for above.
I agree with David, logically the number of floors could decrease as you apply exceptions as well under the current rules.
Interestingly enough I think you could now probably make a case for not reducing the building area/floors since the 90.1-2013 User's Manual clearly states that you should use the entire gross building area to determine the baseline system type (page G-33 to 34). As I had indicated years ago it never made sense to me to reduce the area to determine the baseline system and the 90.1 committee seems to agree. Projects can and do look to subsequent versions of 90.1 to provide answers relative to the ASHRAE 90.1 committee's intent when the currently used version in LEED is unclear. When this was originally posted 90.1-2013 had not been released yet and I had not really gone back to take a look at this particular issue. So thanks for bringing it up again Josh.
I guess the debate can continue!