Ventilation in unoccupied garage - ASHRAE 62.1
Ventilation in unoccupied garage - ASHRAE 62.1
(OP)
I am working on the HVAC design of a new fire hall building. The fire department is 100% volunteer based and the building will be unoccupied most of the time. The truck bay and bunker room is roughly 6000 square feet; there are 5 truck bays. We have exhaust fans and fresh air intake louvers tied in to sensors (CO, NOx, CO2). The office/training area is served by an HRV with heating coil controlled by occupancy sensor. Reading ASHRAE 62.1, I am trying to determine if constant ventilation is required in the truck bay during unoccupied times. Using the Ventilation Rate Procedure, there is very little information on designing for unoccupied space. Table 6-4 indicates exhaust rates of 0.75 CFM/sq foot for Parking Garage; however, I interpret this as a large garage with lots of traffic. I don't feel Parking Garage suits for the fire hall truck bay.
Any thoughts?
Any thoughts?





RE: Ventilation in unoccupied garage - ASHRAE 62.1
I think you are correct and the ASHRAE Parking Garage rate is not the best source.
With all of this being said, you will have to refer to your Authority Having Jurisdiction for the final say.
Justin K, P.E.
http://www.engproguides.com
RE: Ventilation in unoccupied garage - ASHRAE 62.1
RE: Ventilation in unoccupied garage - ASHRAE 62.1
that often means car park fans are quite large but are idling most of time. you can freely say that car park is unoccupied 24 hours a day - presence of people is negligible - but ventilation controlled by sensors must be on all the time.
this applies to car parks, not to repair garages.
RE: Ventilation in unoccupied garage - ASHRAE 62.1
RE: Ventilation in unoccupied garage - ASHRAE 62.1
A dedicated tailpipe collection system is not required in this case; we have cleared it with the appropriate authorities.
RE: Ventilation in unoccupied garage - ASHRAE 62.1
RE: Ventilation in unoccupied garage - ASHRAE 62.1
as you have to design fans for mandatory extraction, they will inevitably be larger and to avoid speed adjustments and permanent cooling of structures, something like 5 minutes fan work per hour, no matter whether sensors will trigger or not, would work if jurisdiction allows it, and, of course, local habits can have influence as well.
RE: Ventilation in unoccupied garage - ASHRAE 62.1
Drazen: Thanks for your recommendation. We were considering interval ventilation as opposed to continuous as well. If we go with an HRV, we could allow for continuous ventilation when the truck bay is occupied and doors are closed (in winter for example). We are currently discussing with the AHJ.
RE: Ventilation in unoccupied garage - ASHRAE 62.1
RE: Ventilation in unoccupied garage - ASHRAE 62.1
as i always use intermittent ventilation, i do not fully comprehend utilization of continuous ventilation with hrv so I became curious
RE: Ventilation in unoccupied garage - ASHRAE 62.1
We have received approval from AHJ for the following installation: Exhaust fans & fresh air intakes controlled by NOx and CO sensors. Small HRV for intermittent ventilation to provide fresh air to the space and control humidity (we agree that continuous is overkill).