HVAC requirements for Automatic Carwash

[doopedeng]

Hi all,
I have a client who is building a car dealership (in Atlantic Canada) with an attached automatic carwash bay to wash every car that goes through its service department. The vehicle is driven into the service drive-through for write-up, then either to service bays or to the carwash (not sure which will come first). The vehicles will exit the carwash into a short detail bay (presumably for drying off), so the washbay is essentially internal to the building. ASHRAE 62.1 requires an exhaust rate of 0.75 CFM/ft2 (most like a parking garage), so with a continuous exhaust of 850 CFM I'm concerned about energy use if we just exhaust and makeup that air without recovering any of the heat. I was thinking of using an HRV, but am concerned about the core frosting up. Also, the typical HRV defrost cycle would shut down the exhaust for significant time periods. Does anyone have any experience in designing the air systems for a carwash, and is willing to share thoughts? What would be the best way to heat a space like this and prevent cold drafts on the poor soul who gets to dry cars all day in the detail bay at the carwash exit? Hot water air curtain at entrance and exit maybe?

Thanks in advance for any help you can provide.
Dooped

 

[Drazen]

you cannot exhaust water mist, check where your recommendation applies, 62.1 has many asterisks and general notes to be read before using tables.

 

[EnergyProfessional]

If your climate is cold, yes ERV freezing will be a problem due to near 100% RH.
Most of the time i see people in washbays they leave their cars idling (i don't). so the 0.75 cfm seems justified unless you legally can put up a sign to disallow idling and have the AHJ not require the exhaust. Obviously asking JHA would be a good idea.

One could argue about natural ventilation if the doors are open.. but it seems this is inside enclosed space. Maybe exhaust that shop air through the washbay? So you only waste the heat from the air you already had to waste from their other operation? Provide fresh air to the shop, and exhaust through the carwash? Obviously this limits your use of ERV int he shop or sales floor.

Make a list with all the ventilation, exhaust and transfer requirements and you may come up with something.

 

[ZDR1985]

Check this out. This might help.

http://www.eng-tips.com/viewthread.cfm?qid=315933