eQuesters

I'm having some difficulty with properly modeling exhaust fans in for LEED and I'm hoping someone can provide me with some guidance.

Here's my problem: I can enter the exhaust volumes and associated KW/cfm for each zone where necessary, but some of the spaces have design exhaust volumes greater than design supply air volumes (negative pressure rooms). If I select "infiltration" or "balanced infiltration" as the source of exhaust makeup for these zones, then the unmet hours for that zone become very high. If I select "air handler" as the source of makeup air, then eQuest increases the design supply air volume to match the exhaust air volume for that zone. This is problematic because the SV-A reports now have values that do not match my mechanical schedules. Additionally, the energy consumption associated with those systems increases as a result of the increased supply air volume. All in all, it's just not an accurate representation of the design. Most of these zones are expected to make up the air through zonal air transfer (something I realize eQuest is unable to do).

At this point, I'm considering adding the exhaust energy as a direct load to my meter along with appropriate usage schedules, and associating it to "ventilation fans". I believe the net effect on energy consumption and peak demand should be the same as if the exhaust fans were explicitly modeled. However, I'm curious as to any dynamic system or thermal effects that I may be circumventing by not explicitly modeling the exhaust fans for each zone. My gut feeling is that there shouldn't be much of an effect, but I'm just not sure. I'm also concerned that by modeling exhaust energy as a direct load, rather than explicitly, the SV-A reports won't show any exhaust volumes and thereby call attention as to the validity of the model.

At this point, I would like the guidance of some of the members on this forum that have more experience with these issues. Is this even an acceptable way to account for exhaust fan energy for LEED? I'm open to any suggestions from anyone who has run into these issues and/or may have experience in how to deal with it.

Thanks in advance

Seun Odukomaiya, EIT, LEED AP