I understand that critical zones are zones that require the largest outdoor air fraction. In practice, does this equate to only densely occupied zones (zones with a people density larger than 25 people/1000 sf)? If this assumption is correct, is there a source that confirms it?
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Dave Hubka
Practice Leader - SustainabilityEUA
LEEDuser Expert
495 thumbs up
November 6, 2019 - 12:47 pm
The potentially critical zone might not be a densely occupied zone.
We have seen that an office, with one occupant, may be the critical zone. This is typically caused by a low supply air volume to this space. So rather than increase outdoor air rate at the system level, we increase the supply air rate to this zone so that it no longer is the critical zone.
RDK E&S
Energy Engineer / Sustainability SpecialistNV5
15 thumbs up
November 6, 2019 - 12:50 pm
Thanks David - is there a way to efficiently screen rooms that may be potentially critical zones? It's unclear to me how only inputting critical zones in the calculator saves time if we need to review each room to ensure they are not a critical zone.
Dave Hubka
Practice Leader - SustainabilityEUA
LEEDuser Expert
495 thumbs up
November 7, 2019 - 10:38 am
I would suggest that you create your own ventilation calculator with one office, one conference room, one reception room, one classroom, and one breakroom. Increase/decrease airflows for each room and you'll begin to see patterns as to when a room becomes critical.
You can take these learnings and better understand which rooms could be "critical" when looking at HVAC plans. Hence not requiring to enter every room.
Hope this helps!