Hi, I am starting work on a laboratory building and have been looking at the standards to see how they apply. The project will use both an ASHRAE 90.1 2007 and 2010 baseline building (one of LEED target and the other for separate project target). My questions are:
1) Bypass air to maintain exhaust stack minimum air flow requirements for plume. Can this be classed as process energy as it never goes into the space? I think it is
2) ASHRAE 90.1 2007 says the baseline should reduce exhaust and makeup air volume to 50% of design values during unoccupied periods – If this is not allowed by the AHJ would the requirement to have the full ACH at all times (or as specified by AHJ) in the proposed supersede this statement for the baseline so the rates match.
Thanks
Victoria
Julia Weatherby
PresidentWeatherby Design & Co. Engineers
94 thumbs up
October 23, 2014 - 7:44 am
Hello, Victoria-
1. I believe it's okay to classify fume hood exhaust (or the bypass air for fume hood exhaust) as process energy. However, it might be simpler to include all the fan energy in the HVAC energy. Process energy should normally be the same in the baseline and in the proposed, unless you have a well-documented special calculation showing process energy savings for a particular process.
2. I believe the way to model the makeup air would be to have both the baseline and the proposed reduce the makeup air to 50% during unoccupied periods. This is an ASHRAE 90.1-2007 energy model for LEED, not an energy model to accurately represent the energy use of the building. It's not really relevant that you won't actually be reducing the makeup air to 50% when unoccupied. You still have to model it that way to have the baseline and the proposed rates of ventilation match and to comply with ASHRAE 90.1-2007. (You may do something different for your ASHRAE 90.1-2010 model, depending on the purpose of that model.)
-Julia