Condensation During Winter Storage

Weird, I've only noticed condensation issues (mildew smell) in the summer in the mid Atlantic area. We had an older camper before our new one and we would notice the mildew smell (like I remember all older campers smelling) in the summer. I decided to purchase two roof vent covers and leave my vents cracked (one vent in front bedroom, one vent in back bathroom). Ever since then I have had ZERO mildew smells.

Now I am fortunate enough to have a metal carport to park under at home and leave the some windows open and roof vents cracked. Not a single odor yet! I think the very best thing for trailers is to allow them to acclimate to the outside temp and humidity. Closing it off is still going to allow humidity to enter, but maybe not allow enough fresh air to dissipate the humidity.

Our fifth wheel sits out, uncovered, all winter here in Utah.
Dry and usually cold winters.
We leave the covered roof vents open and don't have an issue.
Just went inside and it is 35 deg. with the outside air temp at 45 deg.

OP here. I think the condensation issue comes up when the temps rise and fall. In the early or late winter we can have night time temps in the 20's and days in the 60's. To use a real compressor dehumidifier isn't practical because the water in them would freeze. Same thing happens with the Damp-Rid tubs. They freeze over night and stay that way for most if not all of the day. It's not like the RV goes up to 60 inside along with the outside temp. It stays pretty cold, slowly following the outside temps, slower still if covered.

A quick look at the outdoor thermometer shows at 6 am that it's 33 degrees and humidity is 54%, not exactly dry and probably higher if it were to be a rainy day instead of perfectly clear. So if inside the trailer is the same temp and humidity right now, and the outside temp goes into the 50's or even 60's in a few hours, might we have condensation with the cold inside temp and warm outside?

Condensation is a problem in all climates.

I'd disagree with this. The relative humidity in Winter, in Northern tier states and on the Great Plains is low. I'd bet the same is true for West Texas.

Condensation is a problem in all climates.

What I did for a few years, was buy the large, 64 ounce, Damp-Rid containers, place them in tubs or 5 gallon buckets (as additional insurance so they don't spill, since the main ingredient is calcium chloride, which is quite corrosive), and place those in critical places. One went into the living room, another, the bathtub. All of them were put in my RV checklist, so they were secured before I moved the rig, and I also secured them, so if I did move the RV, the containers would not shift and disgorge their contents.

If I had the ability to have power to the RV, I'd do something completely different. I would avoid the Peltier-based dehumidifiers (they are next to worthless for anything bigger than the cubic footage of a kitchen cabinet, in my experience), and go for a real, compressor-based dehumidifier... one that is intended to deal with pints, not ounces of water. Then, I'd close the rig up, and call it done. As stated above, properly winterized, there isn't enough moisture in the air below freezing to cause issues.

When we had the TT, I opened the vents (under MaxAire covers) and cracked one window. In 12 winters in Ohio and WV, never a problem with mildew. This after camping in late fall and thus starting storage with a lot of moisture inside.

Cold winter air holds very little moisture. Warm air (especially in Ohio, less so here in the mountains) holds a lot of moisture. The last thing you want to do is shut an RV up tight with moist air trapped inside when the weather is getting colder.

Ventilate! So long as the excess moisture can find its way out, it will try to do so. No excess moisture, no mildew.

Wayne

No RV cover, all vents open about 2" under Maxx Airs, and use two of the 4 lb buckets of Damp Rid. One goes on the dinette table up front and the other on the throne in the bathroom.

Never an issue.

westend wrote:
A lot of this issue is dependent on seasonal ambient conditions. If you live in a cold zone, the relative humidity is low. If you live in FL or BC it is very humid. IIRC, our relative humidity in MN, in Winter is < 20%. I install Aprilaire humidifiers for customers, on occasion. I make no special efforts for the TT, keeping it mostly closed up the entire Winter.

It varies drastically here. Today and it is dry and the RH is 39%. Yesterday we had a front go through and it was close to 90%.

I just use a 4 lb bucket of "Damp-Rid" One bucket lasts the whole winter, is not messy since you have no open crystals and you can tell when the material is saturated and time to change with the built in indicator. . You can get them on Amazon for $9.47 or probably at Walmart. They work great and keep my TT ( and boat cabin) dry and not smelling musty. Have used for years. I also keep 2 in my basement to keep it smelling fresh and the air dry.

A lot of this issue is dependent on seasonal ambient conditions. If you live in a cold zone, the relative humidity is low. If you live in FL or BC it is very humid. IIRC, our relative humidity in MN, in Winter is < 20%. I install Aprilaire humidifiers for customers, on occasion. I make no special efforts for the TT, keeping it mostly closed up the entire Winter.