I am designing the truck bays at a fire station. The arrangement most closely resembles a parking garage. I am reading Ashrae 62 to require a constant run fan (assuming doors shut) with .75cfm/ft2. I also have a Plymovent system for all the trucks which is the hose attached directly to the truck exhaust with a demand only fan that only runs when the engines are on. I can be more energy efficient if I can remove the .75cfm/ft2 fan from the job but I din't see that Ashrae 62 recognises this approach. I could also improve energy if I met only the North Carolina code (based on 2006 IMC) which allows for the installation of a CO sensor. When CO is low enough exhaust rate is .05cfm/ft2. When not low enough its 1.5cfm/ft2. I would like to argue that the .05cfm/ft2 rate will be used all the time since I have the Plymovent system.
Will Leed let me pass the minimum air indoor quality prerequisit with either the Plymivent system without the .75cfm/ft2 fan or pass using the Plymovent system with the NC two exhaust rate approach with the low exhaust rate running 100% of time due to Plymovent?
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David Hubka
Director of OperationsTranswestern Sustainability Services
527 thumbs up
March 30, 2011 - 10:51 am
LEED would require you to meet the 0.75 CFM/sqft rate outlined in ASHRAE 62.1. The control of the system must maintain CO levels, typically no higher than 35 ppm, 100% of the time, regardless of occupied / unoccupied time schedules.
I am currently commissioning the exact system you have described. The project includes a vehicle exhaust system + a general exhaust system. The vehicle exhaust only runs when the vehicles are on, the general exhaust (sized at 0.75 CFM / sqft) runs when the CO level reaches 35 ppm. The general exhast also runs for five hours every 24 hour period regardless of CO levels.
Hope this helps.
Paula Hernandez
MRS.PAH&A
85 thumbs up
May 26, 2011 - 1:58 pm
Would it be necessary, to comply with ASHRAE 62.1, to supply outside in the same proportion?