Still trying to solve my problem of bathroom vent fans that aren't vented anywhere...
Was considering running out the gable, but that's 25' away, plus another 10-15' of duct and a couple of elbows to move from the outside edge of the attic into the center (and up so that I can slope the duct towards the exhust port?)
Trying to figure out if that's a good idea or bad.
Ran across this great answer... How much vent fan throughput do I need for my bathroom? Which as I read it, basically says...the longer the duct, the higher CFM needed. So given my 480 cu. ft. bathroom and estimated equivalent duct length I'd probably need a 70-90cfm fan.
But searching the web also lead me to IRC table M1506.2 Duct Length, which I understand to say that a higher CFM also needs a larger duct.
So I think I'd need to use 6" duct, rather the then 4".
Am I missing something? Confused as to why the answer above seems to penalize 6" (flex) duct when the IRC seems to indicate 6" is a requirement.