Clearing the air.
To the Editor: I was intrigued by the article "Giving Vent" (April). I personally have suggested such systems for HVAC projects I have worked on in the past, only to have those ideas turned down by my employer, or the owner, on the basis that it was too radical or it did not satisfy the design criteria. A couple of comments, however.
A paragraph begins, "One of the more common ways to do this involves mixing recycled air from the exhaust stream with fresh air drawn from outdoors." "Exhaust air" is an incorrect term; it should be "return air." Exhaust air is typically air that is removed from the building toilets, janitor closets, and other spaces required by building codes to be ventilated directly to the outdoors. No HVAC system ever recycles exhaust air.
The second issue I have is with the idea of utilizing the building plumbing sprinkler system as the cooling medium for the radiant cooling panels. The typical fire sprinkler system is closed--that is, no flow. According to physics, "goes into must equal goes out of."
Unless the water in the plumbing sprinkler system is mechanically cooled, the heat removed from the building for cooling will gradually heat up the water in the piping until the temperature of the water approaches the space temperature. Cooling capability will therefore also gradually diminish.
I was pleased to see that the radiant cooling panel condensation concern was acknowledged and discussed, from a "been there, done that" perspective.
Siddhartha Kamath, P.E.