Exceptions to G3.1.1:
(c) If the baseline HVAC system type is 5, 6, 7, or 8, use separate
single-zone systems conforming with the requirements
of System 3 or System 4 (depending on building
heat source) for any zones having special pressurization
relationships, cross-contamination requirements, or code required
minimum circulation rates.
I'm modeling a building that has baseline system 7. If I read this
correctly then all lab spaces will have their own system and that system
will conform to system 3 from table g3.1.1A. Is that correct? If so -
are all of my lab spaces going to be packaged single zone units? That
doesn't seem right - especially since lab spaces are more than 50% of
the building area in this case.
I'd appreciate anyone's help with this.
Thanks
Vikram Sami, LEED AP
Vikram, you should follow the exception (c) if you have a few zones in a larger building that have special requirements, different from the bulk of the System 7. This I think would be intended for cold rooms, server rooms, etc.
For your case with roughly 50% labs and 50% other, you may instead want to use the exception (a) to add a second system type in order to account for differences in space requirements between labs and other spaces.
The design building is probably a good guide - if you are accomplishing your proposed design with one system, then you might find some way to use one system 7. If you have separate lab/office AHUs in the proposed design, then two systems under exception (a) may be called for.
Depending on the size of the lab, you may end up with several System type 3 or 4 in the baseline, but for larger labs I think the intention would be to make two System 7's.
You may also want to look for the Labs21 guide to Appendix G which includes some other unrelated suggestions.
David Eldridge, PE
USGBC also has provided some guidance on the appropriate baseline system for
large laboratories via a few CIRs. Specifically LEED-NC CIR rulings dated
on:
2/27/2007
&
8/13/2007
David Reddy