It looks like it will be a permanent opening. No flapper in the pictures.
You need to consider where the air to replace the exhausted air will come from.

 

Yeah more than likely going to have to cut a hole to the exterior wall. After a little reading on this it seems like it’s preferred to have a negative on the room, so I’ll have to try to find that balance with how much air I bring in. Given it’s a 3 seasons porch it’s probably not very tight to begin with.

 

If a green grass climate, suggest using a whole house dehumidifier with fresh filtered make up air. Exhaust ventilation will suck the home full of outdoor humidity. Using a whole house dehumidifier like a Santa Fe Ultra will keep the place dry and purge all indoor pollutants and the chlorine.

Keep us posted on your thoughts.

Regards Teddy Bear

 

I’m assuming “green grass climate” means not much of a winter season. While the winter in Michigan this year had been strange/mild that’s not typical, so not much of a green grass state for several months out of the the year.

If they don’t intend on using the hot tub in the summer months I’m guessing I can probably get away with just exhaust.

 

If that 3 season porch has aluminum do not put the hot tub in there.

 

Be careful what you get yourself into. Assuming the hot tub uses chlorine for disinfection, the outgassing will corrode many metals in the room, including wiring. Not to mention the toxicity of the gas.

Could be a potential liability.

 

I've seen some of these solutions that have their own problems.
You exhaust the humid air that adds evaporation resulting in cooling the hot tub. The tub is heated resulting in more evaporation. An endless loop. Plus $$$.
One house with an indoor pool had evaporation along with the chlorine. Within a year the chrome was coming off he faucets. Indoor chemical evaporation don't seem like a good idea to me.
Teddy Bear suggested whole house de-humidifier. Sounds like a better idea. Re-heat systems are wasteful.

 

Some good points. They reminded me of a couple important things. Any pool or hot tub needs a well insulate vapor barrier material that covers the warm water when the equipment is in use. Of course a steady trickle of fresh air passing through the space to avoid a build up of all pollutants including chlorine. Some are now going to salt. Closed cell spray foam insulation to avoid moisture moving through the walls and ceiling. Usually the heat from a dehumidifier is mostly welcome to a pool or hot tub area.

Good ideas are welcome here.

Keep us posted.

Regards Teddy Bear