Dear all, We have a facility with lots of process areas having pressurization and code-related minimum circulation rates. As a result, we say that all the process areas HVAC system baseline switch from system 7 to system 3. But also, the administrative part of this project has thermal loads that differ significantly from the rest of the project, therefore, they should also switch from system 7 to system 3. At the end of listing the applicable exceptions, I happen to have a baseline project, which is originally system 7, entirely switched in system 3. Although this is quite positive from the point of view of my project's scoring, I wonder if this is right reading of the Appendix G. It is the combination of the two exceptions that makes it so. But if my process areas are swithced to system 3 due to exception c, should I still consider exception b? Is there a "linear" way of reading these exceptions or should I say "because most of the project is in system 3, the exception b does not apply and my administration building stays in system 7"? Thank you for the help, With Best Regards,

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 12/26/2012 - 16:31

Take the square footage of the predominant condition (likely the process areas) and enter table G3.1.1A. Select the system. If heated only you can use system 9 or 10 from 90.1-2010. You can then apply exception b to the administrative areas and likely model system 3. You can not take an exception for both areas.

Valentin Grimaud

Thermal Engineer

TERAO Green Building Engineering

LEEDuser Basic Member

28 thumbs up

Mon, 12/31/2012 - 10:06

Hi, The thing is that my project falls under the 90.1-2007 according to the project's registration date and corresponding rating system. I thought so that I could not apply exceptions to both areas (but where is it written?). Moreover, process areas are heavily cooled. Therefore, I take the predominant condition, indeed the process area, and I go to table G3.1.1A. System 7 corresponds to my case. Then I apply the exception G3.1.1c which makes the system 7 becomes system 3. Then, the predominant condition for my project becomes system 3. Therefore is the remaining administration area just system 7 as a consequence of the initial category of the project or does it become also system 3, not because of the exception, but because according to table G3.1.1.A? The process area is quite an exception because of the process requirements in regards to overpressurization. I am not sure how to not end up with system 3 only baseline model...

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 12/31/2012 - 17:03

You can apply addenda to 90.1-2007 and this would allow the use of system 9 or 10 but it sounds like it does not help you anyway. The note under Table G3.1.1A indicates you must apply the predominant condition. You then apply exceptions. It is just implied logic that you cannot have a project made up of exceptions - exceptions to what? You cannot take an exception to your predominant condition. Since the System 7 was selected based on the predominant condition you then apply exceptions to areas outside the predominant area. Given the widespread applicability of exceptions in your case perhaps you could break your project down into more distinct areas so that the exceptions might apply to a larger area. But you cannot have the entire baseline system comprised of exceptions. A significant percentage of the project must me modeled using one of the systems from Table G3.1.1A.

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