Monday, November 19, 2012

Ignorance is Bliss

I spent three days in upstate New York last week. I was presenting “The Basics of Air Distribution” to a Young Engineers at ASHRAE (YEA) in Rochester. I also made a few calls on design engineers. As I have said before, it is a bit surprising how few practicing engineers have a full understanding of the requirements of ASHRAE Standard 62.1 (2010) Ventilation Rate Procedure and recommendations regarding the ASHRAE Comfort Standard (55-2010). Standard 62.1 is referenced in the 2009 International Building Code, which has been adopted fully or in part by most local codes. While I expected some of the young engineers to be ignorant of the requirements, it is always a bit of a surprise when no one in the room knows the overhead heating rule: Maximum delta-t (difference between room and discharge), when heating from the ceiling is 15°F. Exceeding this has two consequences:

1.) 25% more outside air must be supplied to that zone (per 62.1 VRP). I would assume that when one is in heating mode, the outside air is cold.

2.) One can no longer claim compliance to ASHRAE 55-2012, Thermal Comfort, as there will certainly be more than 5.4F thermal stratification in the occupied zone. While Standard 55 is not a part of the Mechanical code like 62.1, it is often referenced. When it is more fully restated in code language (in progress) I expect it will become code in many locations.

Some engineering firms, to their credit, have internal standards limiting discharge temperatures. The engineers I speak to in these firms are glad to finally know why this seemingly arbitrary rule has been put in place.

Surprisingly, I still get push-back from engineers who claim they have been exceeding that for years and no one has complained. This is notwithstanding the fact that the Building Operators and Managers Assn. survey had shown dissatisfaction with the thermal environment continues to be the #1 reason for not renewing the lease in a high rise office.

I guess what they say is true: Ignorance is bliss.

Authored by: Dan Int-Hout, Chief Engineer Krueger