Terrible condensation/mold? What to use to prevent

Mold only grows where the air is damp. Trailers are not air tight nor can they be made air tight. Dehumidifiers pull a ton of water out of the air. Rid-ex or rice or whatever...….not so much.

IMHO a dehumidifier is your only option unless you want mold growing in your trailer all the time.

PS it will grow where you can't see it or even get to it. IOW's mold is REALLY hard to get rid of.

A Dehumidifier is your best bet.
I understand you were trying to avoid using one, but that's the way to go.
I redid an old camper this Spring. It had some Mold issues.
It took me a while to get it taken care of. (It had a leaky roof)
After I got it waterproof, I went around the windows and fixed a couple of poor fits.
I added rubber around the door to help keep out the cold/water too.
Working on my storage compartments was a little bit of work too...
I worked on that old camper Feb till May. Finally fixed most things on my list.
By far, the Mold was the most annoying to work on. Nasty stuff.
Work on yours a little at a time, get it right, then go camping...
I said that like it was easy... NOT EASY.

You apparently have a very humid environment where you store the TT. We keep a large bucket of cat litter open in our living area, a large bowl in the bathroom and another in our bedroom. Ours is stored uncovered outside and we have never had a mold issue.

Mine is kept in a seasonal campgrounds all the time. It is closed up for 8 months winter season a year. I have MaxAir covers on the roof vents. For the first two years we left the roof vent OPEN all winter. No problem. The third year we forgot and left them closed. Have you ever tried to clean mold off of mini blinds??? This year we left them open again and were very pleased to come back to no mold anywhere. I don't know if being up in the mountains of Hinsdale MA at 1450' has anything to do with it but it does work. Local RV repair tech informed me of this. Now if I was down in Florida I would not dream of trying that. My house is locked up tight and the A/C is set at 84 degrees and no body is home. Humidity stays around 50%

While we are here we run the dehumidifier if the heater is on. No wet windows and walls that way. If we don't use the dehumidifier with the furnace all the windows fog up on the inside. Water will run down the wall. It all has to do with where you live.

When I winterize out TT and/or park it for an extended period between uses, I use Damp-Rid hanging bags and small pails to help keep it dry. I hang a bag in the main part of the TT and open all the cabinets and doors. I put the little pails full of the calcium (what is used to absorb water) in the storage compartments. When using absorbing products like this, CLOSE all the windows and vents - you are not trying to "dry" the outdoors!

Works well for our 21 foot camper. Larger campers may need more things done.

Throw out stuff if it is really nasty with mold, but usually I just clean off mold with something like Chlorox Cleanup (something heavy on the cleaning / bleaching stuff).

I am in PA so the weather is much the same. I keep the trailer in a pole barn with it closed up tight. The floor is concrete which probably helps. There is condensation on the outside when the temperatures change quickly and humidity is high, but never inside. My theory is that you get the condensation from letting it open, exposing the cold surfaces to outside air.

I like the idea of opening all the windows and the ceiling vents to have as much air flow as possible. We also have the Maxxair covers which, I think, should be standard.

Turtle n Peeps wrote:
Mold only grows where the air is damp.

This is partially correct. Mold also has to have a food source. That is why a closed brand new refrigerator never has mold but one that has been used will grow mold quickly when the door is left closed.

You are very correct about a dehumidifier!

My 21 year old 32' trailer sits in a trailer shed that is open the last 4' on the sides for air flow.
I close all the windows but leave 3 roof vents, with Maxx air covers, cracked about 1/2".
Also we leave the trailer out for a couple of days in the sun after use to dry the interior out. No mold issues.

My son lives in mid FL about 25 miles from the coast. He keeps his trailer in a closed trailer barn with the windows closed and the roof vents cracked open a bit. He keeps three buckets of DampRid in the trailer for their humid environment being close to the coast.

Mold issues vary depending on where one lives and how they battle or not battle the issue.

Thanks to the EPA nannies, there used to be a hanging product that stopped mold completely... but you can't get it anymore. I looked several years ago and there was nothing equivalent