You don't want a vent fan inside a steam shower, so it will be located in proximity to the shower, but outside the enclosure. The transom gives you the option to allow water vapor to be vented during a regular shower.

Who is building this steam shower ? That whole structure needs to be done to not allow steam to escape from it into the room . IMO poorly done will cost you more than you can imagine with mold adn moisture you cannot get rid of. I use prefab steam rooms for my clients so much less ecpensive than trying to do one in a renovation. A 9' door would be very heavy and not way to seal properly when the stam is in use . I have no idea what you are talikng about as far arunning cold water to stop the steam .

@SH I've got a slope of a couple inches but lots of grout lines on the ceiling for water to potentially get trapped on. So you think that if you could open up a transom at the ceiling when necessary that it would dry out better with more direct airflow? I definitely got the low iron glass.

Hi Paul, Ive got some ideas for you. Perhaps the transom is made just like a shower door with hinges that allow it to open like the shower door or flip up with the hinges on the ceiling? Pleas feel free to reach out to me, the consultation would be no-charge for 30 minutes :-) Darren

I’m no pro, but yes, I think if we had a transom that could open it would help the ceiling dry out better. Specifically because we have the fan right outside that seems to help a lot, but you can tell it’s not really helping with the last foot or so that is covered by glass at the top. If it had been properly sloped I think we would have been fine. I ended up buying an extendable squeegee that I use to get the water off the ceiling at the end of a shower or steam. We used giant tiles and thin grout, so we only have 4 grout lines on the ceiling, and I haven’t noticed if water sticks more to the grout or not.

At the end of the day, I really don’t think you’ll have a lot of residual steam anyway, when you’re done showering. I love steam showers and I’ve had them for years, a minute or so after you shut off the steam, it seems to really die down, true it does stick to the ceiling, but as long as it has a good waterproofing of some kind or as you say tile, there really isn’t an issue. Also, I think you’re fine with the fan you have just outside the shower, you might want to pump up the horsepower a little with a new $100 unit but these moisture sensing units are quite good. You also did mention a moisture sensing fan in the toilet room, you might consider one with a switch instead of a moisture sensor or as you probably won’t get any moisture there, so the fan won’t turn on