Sorry it took so long to reply. My computer crashed and I have been working my way through the recovery disks. I am typing this at work.
I bought the fan online from an outfit in Buffalo. It is an industrial stength fan with a long guarantee. They shipped it to a store here in Pittsburgh. If I keep the windows open and the humidistat set at 70%, the fan never comes on. But with the windows closed, it will run until it draws enough dry air from inside the house to balance the tub.
The fan is mounted outside at the peak of the roof about a 20 foot run away from the tub. An insulated flex duct runs from the grille in the wall near the ceiling through the attic to the fan. The fan is very quiet and all you hear is air movement.
Venting into the attic is bad news. It will make the insulation damp and useless.
We have tile in this house and the two condos in Florida. It is nice, but might be tough to maintain with an indoor hot tub. Even if you silicone the grout it would get mouldy in time unless you keep after it. We don't even mop up the water when we get out. It just evaporates in an hour or so. We only mop with routine cleaning and after we get "frisky" in the tub. We have 2 feet of clearance on 2 sides, 14 inches on one side and 7 feet on the other: plenty of air circulation.
If I had to do it over, I would skip the fan and just open the windows.
Thanks Term. Those pics are old and we made some improvements since then. If I can ever make the computer work again I might post an updated pic if ya'll promise not to make fun of me again.