The building has four space types and 20 AHUs. The building lacks any integrated controls, so each AHU operates independent of the other. The building has primarily open floor plans, with a few conference rooms and private offices (for 1 person). 20 VRP calculators were completed - one for each AHU, with most AHUs having two zones. The conference rooms are included as a separate zone, as is the cafeteria. Most AHUs serve 6,000 SF or less (some serve only 2,000). The largest AHU serves 25,000 SF.
Our LEED Review comment was "a sufficient number of potentially critical zones have not been identi!ed in the supporting calculations in all cases. Zone level data is used to calculate the required outdoor air at the system level. The documentation must provide sufficient information to show that all potentially critical occupiable zones have been accounted for in the calculations to determine the critical zone. Only a few zones have been
entered in the calculations for each supply air fan. For single air handlers serving over 100,000 square feet, a minimum of 15 zones should
be listed in the VRP calculations for each of the large air handlers. Fewer zones are acceptable for smaller air handlers. Critical zones
generally include conference rooms, training rooms, or other high density spaces with variable occupancy, though office spaces or other
spaces may be the critical zone if the volume of air supplied to the space is limited."
I have a few questions:
1. Do we need to breakout each of the private offices as a separate zone (even though it's not treated as such by the AHUs)?
2. We have 20+ critical zones and have no AHU serving 100k square feet. How would you respond to this comment?
3. Last, we've been treating each of the AHUs as a separate 'system'. Do we need to send over a single calculator, that includes all zones from the smaller AHUs and aggregate all AHU information into one (make-believe) 'system calculator'.?
Thanks
Aaron
Ante Vulin
Sustainability ManagerYR&G
80 thumbs up
December 11, 2012 - 1:47 pm
A ventilation zone is different from a thermal zone. So while a single VAV box may serve three offices, each of those offices should be considered separately for ventilation purposes, especially if they have different primary air flows.
If you are only providing one or two potential critical zones in your 62MZ calculator, it may not be clear that those zones are actually the system critical zones, especially if the zones listed in your calculator represent combined spaces.
So in response to your questions:
1. Yes, unless you can clearly show that conference rooms or other rooms are the actual critical zones .
2. Your response narrative must make it clear how potential critical zones were selected.
3. Each AHU should be treated as a single system.