Humidity control: what to do first?

[Hohn]

So if you condition the interior space, I suggest you also apply a poly vapor barrier to retard the moist air passing through the walls.

See post above. Vapor barrier in the midwest is almost always a bad idea unless you have somehow installed it in a way that it can never have condensation at any time all year round.

That's next to impossible to do with our climate.

 

[Hohn]

Ventilation. Lot's of it.
Zim

Probably needs the opposite. Sending the air inside to the outside means more air (and humidity) pulled in from outside.

That's counterproductive.

The only real option here is seal things up as air tight as possible and run all the dehumidification you can to try lower the dew point inside as low as you practically can.

Even if you have just a sheetmetal box, you can prevent moisture as long as 1) the interior dew point is always less than all surface temps, and 2) the surfaces are always warmer than any dewpoint they contact.
The last part is tricky when you're cranking up air conditioning on the inside to try to be comfortable and you have ripping hot metal sheets on the outside.
If you have a sheetmetal box that's leaky and crank up air conditioning inside, you'll get condensation (and mold) on the cold interior surfaces closest to the outside where that high dew point air is touching them before its been dried.

 

[Hohn]

Dehumidification is a really important part of any summer comfort-- air conditioning alone is NOT sufficient. A/C does dry air out a good bit, but most of the time you'll find you are running the thermostat much cooler than normal because you want dryer air, not because you are hot.
A single basement dehumidifier makes such a difference in the entire house that we can run the thermostat at 77-78 in this summer heat and be comfortable when before we'd need to run 74 or so.

 

[racecougar]

Dehumidification is a really important part of any summer comfort-- air conditioning alone is NOT sufficient. A/C does dry air out a good bit, but most of the time you'll find you are running the thermostat much cooler than normal because you want dryer air, not because you are hot.
A single basement dehumidifier makes such a difference in the entire house that we can run the thermostat at 77-78 in this summer heat and be comfortable when before we'd need to run 74 or so.

That gets back to running a load calc to size the mini split appropriately for the OP's specific conditions (humidity included). A good inverter system will run low and slow, which is excellent for pulling humidity down.

 

[zimman]

Probably needs the opposite. Sending the air inside to the outside means more air (and humidity) pulled in from outside.

That's counterproductive.

The only real option here is seal things up as air tight as possible and run all the dehumidification you can to try lower the dew point inside as low as you practically can.

Even if you have just a sheetmetal box, you can prevent moisture as long as 1) the interior dew point is always less than all surface temps, and 2) the surfaces are always warmer than any dewpoint they contact.
The last part is tricky when you're cranking up air conditioning on the inside to try to be comfortable and you have ripping hot metal sheets on the outside.
If you have a sheetmetal box that's leaky and crank up air conditioning inside, you'll get condensation (and mold) on the cold interior surfaces closest to the outside where that high dew point air is touching them before its been dried.

I'm not a rocket scientist like some on here. This guy has what amounts to an abandoned house with no AC or heat.
If you introduce AC and or Heat that's blowing air of whatever temperature. Blowing air whether hot or cold is ventilation in my simple mind. It's moving air.
You call it whatever with all the fancy words or percentages or formulas or whatever.
I'm good with what I said.
Zim

 

[dcg9381]

In your opinion, what should I do first? Any contractors you would recommend in the NE IN/NW OH/S MI area?
Is double bubble useful? I have a source that will give quite a lot of it.

Maybe nothing. Depends.

I had one "uninsulated" pole barn with zero vents (other than the barn doors, which were very leaky). I'm in TX, so it's usually hot, but when we'd get a cold snap (very rare) following high humidity high temp, I'd get condensation on the steel. Because hot humid air inside, condensed on cool steel.

I think this is sorta what's happening to you. Ground temp is very cool, you're getting high temps / high humidity and water is condensing on your "cold" slab.

I wouldn't try to wrap it. That's not going to change condensation on the floor. If I was going to "wrap" it, I'd do it with closed cell foam, but again, won't help condensation on the slab. Probably cheaper than trying to wrap it ineffectively from the inside and less expensive than pulling the exterior and wrapping it.

What I'd try (if I wanted to fix this) is installing mini-splits set on "dehumidify". Bonus is they provide heat and cooling.

 

[mikedodge]

You could always buy a used known working dehumidifier and see what happens.

No matter what you do if the walls aren't sealed properly you're not going to get optimal performance out of whatever you're running.