The bathroom needed a seriously substantial exhaust fan to deal with the copious amounts of steam/water that the custom steam shower is going to produce. I decided to go with an in-line fan with 850 CFM. That just means that there’s a duct opening in the ceiling, and then ductwork that goes back into the crawlspace. In the middle of that duct that leads to outside, the fan is inserted “in-line” so that the noise is contained in the crawlspace. It’s about a 25 ft. run that the fan has to deal with, so it had to be very powerful (and thus fairly loud). With fans/ducts like these, there shouldn’t be a low spot in the ducting since the steam can cause condensation which results in water in the duct that can then mold. The exit route didn’t allow for a nice straight slope, so to combat the condensation, I just made sure the ductwork was very well insulated.
To get the ducts where they needed to be, I had to move several which resulted in only one slice to my finger. Note to self: always wear gloves. Metal is sharp.