Billybob is right, but there is a way out.
Posted by Rogervan on 1/14/2018, 2:56 pm, in reply to "Re: Humidity help"
Well, all this is going to be too much for the poor Original Poster:
It's not a cheap, bad solution, but it does need some tweaking. I'll never forget this in the future, thank you BB. You're right.
I didn't think about the 70% humidity wetting down the surfaces within the walls. I never had to deal with residential high humidity. I think BB has.
Polyethylene sheet has finite permeability to water vapor, but it's very low.
My suggestions would be OK if you stretch 6 mil polyethylene over the floor if it's carpeted. That worked very well for me in the past for 12 months at a time for protection from herp messes, and it stands up to light herp-room foot traffic. Then cover the walls and ceiling with 6 mil poly also. Let the poly on the ceiling hang down about 4-6 inches. It would be better if you lay vertical 1X2 (cheap) wood furring strips flat every 32 inches over the wall studs, then stretch the poly over them.
If the flooring isn't adequately insulated, and if the floor is any kind of finished hardwood, I don't know how to deal with that. Because when the humidified air moves close (1/16th inch) to the floor, since the floor is always colder than the room, water might condense onto the floor, perhaps ruining the finish or damaging the boards. If you live in a high-humidity climate or a cold climate that's below freezing a lot, ask the local contractors how to handle that through-the-floor vapor migration problem. They'll probably say increase the under-floor insulation.
There is one possible problem with ceiling light fixtures, the ones that self-ventilate to keep cool by letting room air escape through the fixture and into the attic. These have been shown in some cases to cause slight mold close to the fixture in the attic insulation. Dust provides the nutrients to the mold.
So for the ceiling, it would help if you replace the bulb(s) with 4 to 5 watt LED bulbs (lumens = to a 60 watt incandescent bulb) to lower the temperature of the fixture, then stuff any vent holes in the electric box or "can" with non-flammable stuff, like the insulation above the ceiling.