Are exceptions mandatory or optional?

John Krutko

Sr Project Manager

Osborn Engineering

LEEDuser Basic Member

1 thumbs up

Project location :

United States

April 28, 2015

Under ASHRAE 90.1 - G3.1.1 do I HAVE to use exception C for any zones having special pressurization relationships, cross contamination requirements, or code-required minimum circulation rates? In my case this exception has a negative impact on my model. Can i stick with system 5? Thanks

Post a reply

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 04/28/2015 - 15:43

You must apply the exceptions under G3.1.1.

John Krutko

Sr Project Manager

Osborn Engineering

LEEDuser Basic Member

1 thumbs up

Wed, 04/29/2015 - 13:14

Marcus, In an energy model for a LEED 2009 project it has been shown acceptable to model Baseline System Exceptions per ASHRAE 2010 G3.1.1 such as modeling a System type 9 or 10 for a heating only thermal zone. The exception in ASHRAE 2007 (G3.1.1 c) for using baseline single zone systems for zones that have code required minimum circulation rates was deleted in ASHRAE 2010 G3.1.1. Since this exception would no longer be allowed under a LEED Version 4 project, it would seem acceptable to follow ASHRAE 2010 and not model it in a LEED 2009 project. Is it acceptable to NOT model this exception (ASHRAE 2007 G3.1.1 c) since under ASHRAE 2010 it is no longer allowed?

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 04/29/2015 - 13:23

Modeling a system 9 or 10 is allowed by addendum to 90.1-2007. If you can find an addendum to 90.1-2007 that eliminated exception c then you can use it. Keep in mind you must use it in its entirety. If it was not changed by addendum then you can't use it.