We live in central IL and have a Bullfrog 451 in a 10’X25’ room that was built on a patio.
I'm also putting a spa inside, shoehorning into a 12 x 12 room. I like the idea of the top down bottom up shades, as we are installing double hung windows with outside screens. My idea is if the wind is strong, we can open the top sections and still be sheltered sitting in the spa.
What kind of floor covering treatment did you use? We have a concrete base, debating on tile, acid staining, or some type of commercial rubber coating. In a 12 x 12 room with a 7.5 x 7.5 tub, not much floor will be showing. Since it's part of the main house slab, I can't have any moisture transfer thru the floor.
I also planned using white vinyl bead board for the ceiling (actually what I'm looking at is AZEK, which I think is pvc). Haven't decided on the walls yet, maybe more AZEK boards, but the windows are Pella vinyls.
Speaking from no real experiences, I would think the spa room wouldn't need any more ventilation than a large master bathroom. For now, our room won't be conditioned, so I plan on installing a ventilator with a variable speed control, and set it for the lowest (quietest) setting that is sufficient.
One of our wet test was in a small private room, not much bigger than ours will be. After 30 minutes of use, I didn't notice any major humidity buildup.
I also have a spare Aprilaire HRV unit laying around. This is a fresh air recovery ventilator that only moves 120 cfm worth of air, but recovers up to 77% of the heating or cooling energy from the exhaust air out of the room. It would help when the outside makeup air is too hot or cold.
Around here, the summers get real humid, so I may be adding some kind of conditioning HVAC equipment later. I have been told that it is better not to include the spa room in the main HVAC system, as the chemicals will eventually affect the equipment. (I'm a former HVAC tech, and this makes sense to me).