Monday, November 7, 2011

"What type of air distribution should I use?"

I get these types of calls all the time. Typically it is a young engineer, often an EIT, who has no idea what is the best way. Often, I get a drawing showing a floor plan or space layout. The problem is that there are other issues that need to be understood.

One example is the theatre - typically stepped, with very high ceilings. It would seem that underfloor or displacement ventilation would be an obvious solution, especially as they are very quiet. But we need to know where the project is, how much heating will be required (typically not much), and what type of air handler is contemplated. Both displacement and underfloor require supply air no colder than 65F, but with a dew point of 55F. This means a typical DX rooftop will be challenged.

Overhead has the problem of getting any heat down to the floor for the warm-up period, but can employ low cost package rooftop systems. Typical ceiling diffusers are impractical to adjust between seasons and the flow to ceiling distance is quite different in the rear than near the front of the theatre.

There are solutions to all these issues, of course, but without knowing a lot more about the project, providing guidance will be difficult.

Authored by: Dan Int-Hout, Chief Engineer Krueger