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NC-2009 EAp2:Minimum Energy Performance

Baseline System? 110,000 sf building w/ code exh requirement

I'm working on a Vehicle Maintenance Facility that is one-story, 110,000 sf with the following breakdown: -approx 85,000 sf of indoor parking -approx 11,000 sf of mechanics bays -approx 14,000 sf of administrative space (offices) The indoor parking and mechanics bays require minimum exhaust rates for CO/NO2 emissions, and based on other threads here, I'm assuming that the indoor parking and mechanics bays are considered the "predominant condition." I'm confused as to how each space's baseline system should be addressed. Based on the overall area, building function, and the fact that we have natural gas would lead me to System 5 being used for the mechanics bays and vehicle parking (the predominant condition), but these spaces have code exhaust requirements and pressurization requirements, which leads me to believe I should be using System 3 (based on G3.1.1c) for these "predominant condition" spaces. Can anyone provide some guidance? Any help is much appreciated.

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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
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Fri, 11/01/2013 - 16:12

Is the indoor parking conditioned space? If not it would not count. Once you identify the predominant condition then you apply any exceptions and use the area of that space to determine the system type.

Mon, 11/04/2013 - 17:39

Thanks for the response. The indoor parking is heated and ventilated--not mechanically cooled. The predominant condition would be the indoor parking, but G3.1.1(c) would apply to this space and make the indoor parking a PSZ system rather than a Packaged VAV with reheat. The overlying question is: if the predominant condition falls under an exception, does the next condition become the predominant condition?
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Marcus Sheffer
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7group / Energy Opportunities
LEEDuser Expert
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Mon, 11/04/2013 - 18:54

I would recommend that you apply a system 9 to the indoor parking as a heated only space. If the mechanics bays are heated and cooled then it sounds like the remainder of the project would be a system 5. The use of a system 9 takes you into ASHRAE 90.1-2010. Within that version you would then apply G3.1.1 Exception (f) which says to use a different baseline system for the heated and cooled spaces. If the mechanics bays are not cooled then it is a system 9 too and the office would be a system 3.

Tue, 11/05/2013 - 01:52

Thanks, Marcus-- This would still apply under ASHRAE 90.1-2007 due to the Addendum "dn", yes? Reason I ask is we're working under LEED v2009 and "dn" covers heating only systems as well.
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Marcus Sheffer
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7group / Energy Opportunities
LEEDuser Expert
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Tue, 11/05/2013 - 14:19

For LEED you can use any addendum to 90.1 as long as you use it in its entirety. Yes is looks like Addendum dn was the one that added these systems. FYI - this addendum refers to these systems as systems 10 and 11. That was a typo in the addendum and they should be referred to as systems 9 and 10.

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