Per 90.1-2007 section 6.4.3.9 "Ventilation Controls for High-Occupancy Areas" systems are required to have DCV given certain criteria. Appendix G seems to not mention anything about ever requiring demand control ventilation, but I always assumed the baseline building had to meet all code requirements elsewhere in 90.1 unless otherwise noted in Appendix G.
If a baseline system meets the criteria to require demand control ventilation per section 6.4.3.9, is it required to be modeled that way? Are there any other similar items dictated by 90.1 that aren't required for the baseline building since Appendix G doesn't mention them or is it as simple as: "it's required unless Appendix G says otherwise"?
Additionally I have the case where one of my systems that may require demand control ventilation on its own is being grouped into a single VAV system per Appendix G. But the rest of the thermal blocks in the VAV system don't require Demand Control Ventilation so how do I account for that?
Matt Scott
EngineerN.E. Fisher & Associates, Inc.
18 thumbs up
September 5, 2013 - 3:37 pm
Well I stumbled onto some text that answers at least part of my question. The exception under G3.1.2.5 says baseline ventilation doesn't have to match proposed ventilation when the proposed system is being modeled with DCV despite not being required by 6.4.3.9. So that implies modeling DCV for the baseline system is required when it is required for the proposed system.
Ok well back to the second part of my question. If only one zone in my VAV system requires demand control ventilation, how do I model this fairly without affecting the other zones?
Anthony Hardman
Building Performance AnalystThe Green Engineer
16 thumbs up
September 5, 2013 - 3:49 pm
G1.2 states that the baseline has to comply with all the mandatory sections of the standard (i.e. 5.4, 6.4 etc.), so yes, DCV would be required in your baseline if the criteria are met. There's a good chance your high density areas have to be on a separate system anyway according to G3.1.1 exception B, in which case you wouldn't have the multi-zone problem you're referring to.
Rudolph Carneiro
HVAC consultantOptimized Systems
26 thumbs up
September 5, 2013 - 4:31 pm
Anthony. Need your input on exception "b" of mandatory section 6.4.3.9
What is meant by the following:
b. multiple zone systems without DDC of individual zones communicating with a central control panel
Are all mutlizone systems exempt from DCV?
Appendix G say that it should be modeled separately, but the mandatory section seems kind of unclear.
Anthony Hardman
Building Performance AnalystThe Green Engineer
16 thumbs up
September 5, 2013 - 4:39 pm
Wrong exception B. Check G3.1.1. Your ventilation/occupancy requirements may yield a condition where your loads exceed the average by > 10BTU/SF.
Matt Scott
EngineerN.E. Fisher & Associates, Inc.
18 thumbs up
September 5, 2013 - 4:45 pm
Anthony, thanks for pointing me to that section. That was exactly what I needed to hear.
Still not sure what to do about the DCV zone mixed in with the non-DCV zones though. I originally had my model with the high density zones on their own systems, but the LEED reviewer rejected it. We compromised and revised the baseline system mapping of the building, resulting in the situation I described above.
It's kind of a moot point since the affected spaces are only occupied a handful of hours per week and the DCV doesn't affect the overall savings too much, but I just want to make the model as fair as possible.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 9, 2013 - 9:37 am
Yes you model DCV in the baseline if it is required by section 6.4.3.9.
So if you have to model a system that covers the entire floor (Systems 5 to 8 under G3.1.1) and have one zone with DCV that does not meet any of the other exceptions under G3.1.1, you would typically need to model a separate system to account for the DCV.
Matt Scott
EngineerN.E. Fisher & Associates, Inc.
18 thumbs up
September 9, 2013 - 11:11 am
Thanks. Would you agree this should be added as an exception to G3.1.1?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
September 9, 2013 - 11:37 am
Quite often these spaces do tend to meet one of the exceptions under G3.1.1 Exceptions (b).