Hi everyone,

I am modeling a residential building with PTACs in all zones in the
baseline case (System type 1). I have toilet exhaust fans that I have
inputted to my design case, but I am wondering how to input the exhaust
fans into the baseline case or not input them at all. Part of my confusion
has come up after digging through the forums. I found two conflicting
suggestions - one that mentions (see attached PDF- Toilet Exhaust; I have
highlighted relevant text) that the fan power listed in ASHRAE 90.1-2007
G3.1.2.9 covers supply, return, exhaust and relief fans; since this is a
constant volume system, assigning all of the fan energy to the supply fan
leaves no energy allowance for the exhaust fan. From what I can understand
from this suggestion, I can model the exhaust fans in the baseline case,
but I will have to distribute the fan energy proportionally among the
exhaust, supply and return & relief (if any) fans. Another suggestion is to
model the exhaust fans in the baseline case with the same parameters (CFM,
KW) as the design case (see the attached PDF-LEED Review comment;
relevant text highlighted) because toilet exhaust fans are typically
independent from the main system that conditions the space (as it is in my
case) and (this is my own interpretation) the fan power listed in G3.1.2.9
is only for "systems".

I am very interested in what kind of comments other users in this forum
have received from USGBC regarding this topic. Suggestions are appreciated.

Thanks,

Ritwik.