I'm trying to figure out the exhaust airflow rates required for chemical pollutant source rooms in a hospital (e.g. janitor's closets, copy rooms, etc.). The LEED credit requirements state: "The pressure differential with the surrounding spaces must be at least 5 Pascals (Pa) on average and 1 Pa at a minimum when the doors to the rooms are closed." This is a bit ambiguous, but I take this to mean that the average exhaust rate of these rooms must meet at least a 5 Pa pressure differential over their entire operating range but the instantaneous pressure differential can get as low as 1 Pa. This implies that LEED is giving allowance for spaces where the chemical use is variable and the exhaust fans have multi-speed control where they ramp up only when chemicals are in use.
Most of the exhaust air systems I work with for these types of spaces are simply equipped with constant volume fans however. So if the exhaust air volumes don't change, then it sounds like we must meet a 5 Pa pressure differential to meet the credit requirements. Is my interpretation correct? Has anyone had experience or LEED comments related to this specific issue? Thanks,
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
January 15, 2014 - 5:30 pm
Scott - correct - you should meet 5 Pa if the volumes don't change
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
January 16, 2014 - 3:43 am
I thought it applied to the measurements. I.e. over ten minutes of measurements at say a measurement every 5 seconds, the average of all measurements must be 5 Pa with a maximum deviation of 4 Pa. Yes, you design for 5 Pa.
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
January 24, 2014 - 9:01 pm
Jean,
In my experience LEED/GBCI has never asked for measured data for this credit. Have you had a LEED reviewer ask you to prove you're meeting the required differential pressure?
Dylan Connelly
Mechanical EngineerIntegral Group
LEEDuser Expert
472 thumbs up
January 24, 2014 - 9:01 pm
Jean,
In my experience LEED/GBCI has never asked for measured data for this credit. Have you had a LEED reviewer ask you to prove you're meeting the required differential pressure?
Jean Marais
b.i.g. Bechtold DesignBuilder Expert832 thumbs up
January 27, 2014 - 5:52 am
We've had projects, some with the submitting measured data and some with providing calculations, and to date have had no questions asked.