hot tub ventilation question

[Carpenter]

     I have been asked to build an addition 20' x 26' to go over a hot tub.  It will be one large room built on a slab with a lot of windows a vaulted ceiling and pine tie beams.  I will mill the tie beams and while not being a timber framed building it will have a nice timbered look.  They will have a hot tub in it and I am a little unsure about additional ventilation required or not required.  I have done a little internet research on the subject and have not found a definative answer. 
     I am hoping that somebody on the forum has done something like this and could help me out.  The building will be in northern Nebraska.  Sometimes we have high humidity and extreme temperatures.  I haven't been around a hot tub much, and never in an enclosed area.  I really can't see it generating as much steam as a shower, but I really have no idea.  The roof itself will be well insulated and ventilated.
   Thanks in advance
   Jeff Carpenter     

[beenthere]

Good that you are giving the potential moisture problem due consideration before construction.

Being as it is hot (warm) water, then would want to know if there will be a cover when not in use. Also, the room temperature will have an effect on the relative humidity of the space and the potential for condensation on cold walls and windows. Any number of combinations can lead to problems or a need to provide different temperatures of dehumidification, or some venting.

[thecfarm]

We have been doing that for years in our sun room. We open up a few windows each time we are in it,because we do not have a fan in that room. If I had known we was going to put one in there I would of put a fan,like for a bathroom in there and used water proof sheet rock. They better have a cover for it,or it will cost them ALOT to keep the water warm. This room is attached to our house too. Yes,there will be alot of steam too. The windows are steamed up each time that we use it. Steams up,but water is not dripping off them. We have wooden stained window sills and the vanish still looks good on them.With ours some consideration comes off the cover every time we use it and onto the floor. It's only from being closed,once it drips of there is no more water.We put towels under that side of the cover.Not much water either,the towels are not dripping with water.We have our cover on an assist lift. It tips up at a 90° angle and we put towels down to catch the water. I would also call the place they brought it from. They sell hot tubs and should know the answers too.

[Ron Wenrich]

I put a hot tub in a small, unheated shed - 8'x10'.  We don't heat it up to 102°, but more like 96-98°.  I heat my water mainly with solar, and I don't use it in the winter months due to expense.  Its also not a very big tub, about 200 gal. 

I have 2 windows in the building.  Sometimes it does get to a point where there's condensation on the windows, especially during cool times of the year.  We do open the windows if the temperature is cool enough.  In the summer, I have panels that I can open up and its like being outside. 

How often are they thinking about using it?  The idea of a hot tub is neat, but the actual usage goes down after the novelty wears off.  The other thing is how long during the year will it be used?  Winter time heating is way expensive, and its the time of year where you'll get the most condensation.   My experience in a small space has been that the condensation is gone by morning. 

[thecfarm]

We use ours only in the winter months. Ours get shut down when it's warm out. We do heat the room too. With the cover on if you went in the room you would have no idea the hot tub was there. Only when we use it the windows get some mositure on them.