[Bldg-sim] Exhaust Air Energy Recovery - 90.1-2010

David Eldridge DEldridge at grummanbutkus.com
Fri Oct 12 14:44:06 PDT 2018

I'd look at these factors:

·        Is the maintenance garage part of exception b for partially heated and not cooled spaces? Just wanted to make sure that one was also considered.

·        Snorkel exhaust clearly toxic and perhaps corrosive, apply exception c.

·        "General" exhaust - the air stream isn't itself at toxic levels as long as the room is maintained within the established bounds, but the contaminants are still toxic (although diluted) - I would say technically the exception c language doesn't say that the airstream is toxic, it says that the system is exhausting toxic fumes - which would still be true for CO and NOx. Mainly the point being: Would there be justification to exclude heat recovery systems that have a potential for cross-over like we do for laboratories?

If you contrast this to a laboratory, the idea is that modulation plus sensible heat recovery can remove the 50% effectiveness requirement, which allows use of a runaround coil to achieve heat recovery at a lower effectiveness but maintain higher air quality as well as potential corrosion of equipment where the options to make a runaround system may be more durable than a heat wheel.

Vehicle CO and NOx might be in the same category as the laboratory chemicals that cause us to avoid any potential for crossover, and which makes heat wheels and their high effectiveness inappropriate for the application. Obviously for a lab you get funneled to which lets you use a less effective system that wouldn't apply to a vehicle facility - the vehicle facility would be exempted instead of passing to a lower requirement, although a runaround system could be considered if the owner still wanted to increase efficiency beyond code.

Similarly you may also encounter an argument for exception h if the two exhaust streams are similar magnitude airflows instead of a 75/25 split, but you could still put a partial heat recovery system on the project for improving over the code requirements.


David S. Eldridge, Jr., P.E., LEED AP BD+C, BEMP, BEAP, HBDP

Direct: (847) 316-9224 | Mobile: (773) 490-5038

Grumman/Butkus Associates | 820 Davis Street, Suite 300 | Evanston, IL 60201
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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jones, Christopher via Bldg-sim
Sent: Thursday, October 11, 2018 9:29 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Exhaust Air Energy Recovery - 90.1-2010

I have a vehicle maintenance garage. It has a typical two exhaust system configuration. The main MUA and associated exhaust fan control the level of CO, NOx, etc. in the space such that the level of contaminates never gets to toxic levels. The second exhaust system consists of snorkels that directly attach to the vehicle exhaust pipe. This system doesn't dilute the exhaust therefore Exception c., "Systems exhausting toxic, flammable, paint, or corrosive fumes or dust".

I am of the opinion that the general make-up air and exhaust system controls the system such that the exhaust is not at the point of being toxic and the exception doesn't apply?

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

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