Condensation Question

[Prem]

Dang! I plum fergot about a vacuum. But then the inner and outer walls would both warp, so I'd end up having to do spray foam any way.



P.S. OverTheTop,

Yeah, BUT yer thermos is always wet on the inside. Uh huh.



P.P.S.
Only my Spanish students call me "professor."

[lrrowe]

Jerry,
Page 18 of your OTTCT post
viewtopic.php?f=42&t=44951&start=255
Shows the wood cross members I was referring to earlier.
I like that idea.

[Quadriderdad]

The biggest part of this question is what climate do you live and camp in? If you are in hot dry climate you won't notice near as much condensation as a cooler moister climate. Provide plenty of ventilation and heat as required and you will minimize the moisture.

[Prem]

Err...guys, most of the moisture *inside* the trailer comes from us exhaling and our skin breathing (normal, constant perspiration, even in winter).

[lrrowe]

Prem,
You or someone else may have addressed this question before, but what would you do to minimize it other then leaving vents or windows open?

[chiefb711]

I was lurking around the site tonight, and found this as a response to the condensation issue.

I thought about it for a second, then thought, "who makes an aluminum sided RV with loads of experience?" Led me right to the Airstream website, and searched for condensation in one of their owner manuals.

TIPS TO CONTROLLING CONDENSATION
To avoid condensation problems, try to follow these tips to help alleviate excess moisture.
*Allow excess moisture to escape to the outside when bathing, washing dishes, hair drying, laundering, and using appliances and non-vented gas burners.
*Always use the vent hood when cooking.
*Keep the bathroom door closed and the vent or window open when bathing and for a period of time after you have finished.
*Do not hang wet clothes in the trailer to dry.
*In hot weather, start the air conditioner early as it removes excess humidity from the air while lowering the temperature.
*Keep the temperature as reasonably cool during cold weather as possible. The warmer the vehicle, the more cold exterior temperatures and warm interior temperatures will collide on wall surfaces, thus creating condensation.
*Use a fan to keep air circulating inside the vehicle so condensation and mildew cannot form in dead air spaces. Allow air to circulate inside closets and cabinets (leave doors partially open). Please keep in mind that a closed cabinet full of stored goods prevents
circulation and allows the exterior temperature to cause condensation.
*The natural tendency would be to close the vehicle tightly during cold weather. This will actually compound the problem. Simply put, you need to remove some of the warm air, and allow some cool outside air to get inside the vehicle, so the furnace will not recycle the humid interior air.

Some of this seems like common sense, but it goes on further to explain the issues that might come about with using the trailer for prolonged living quarters. Thought it might help those looking for answers.

Respectfully

Ryan

[Prem]

Bob, you can use a dehumidifier if plugged into 120v house current, or install a woodstove. The best, as I keep saying from personal experience, is spray foam insulating the bare aluminum walls on the inside.

As for the Airstream, I've seen my Airstream restorer friend Neal completely strip two of them Ryan. They had very thin fiberglass batting rubber undercoat glued to the inside of the skin. The condensation ran down onto the steel floor cross members inside the aluminum belly pan. Rust. Rusted out. The fiberglass was streaked black with bacteria or mold.

For what it's worth.

[AZ_Desert_Rat]

The first time I camped out in a cargo trailer (my buddy's) was in early December in Arizona. The nights were down in the low 30's with a little frost. Everything was fine until we turned a small heater on to take the chill off and put on a coffee pot ... the condensation literally rained on us!

When I bought mine, I had it insulated and what a difference ... I have had no issues and camped in it early December 2013 traveling between Minnesota and Arizona; and it was plenty cold!

As others have said, it is a tin sided trailer and when the outside is cold and the inside is warm, the metal condenses ... insulation and ventilation helps to reduce the condensation.

Good luck with your project...

[OverTheTopCargoTrailer]

AZ_Desert_Rat

I just noticed - you need to change your name to

MN_Mountain_Rat



Prem ....... I'm never getting inside another moldie Airstream ever again

[cornfused]

The other thing you guys are forgetting is a lot of us use the "buddy" style heaters to heat the trailer. Go back to your chemistry classes, and what is a byproduct of burning propane? H20! If you use a "non vented" propane heat source you will also add to the condensation problem. The other thing is that warmer air can hold more water in it than cooler air. This is why it is still helpful to ventilate the trailer in the winter with the heater on. In affect the ventilation will act like a dehumidifier because the warmer air will have more moisture in it than the cooler air coming in.

This is why I'm planning on switching from a buddy style heater to a forced air diesel "bunk heater" this winter.

[lrrowe]

I hated chemistry. In college I barely got by and accepted all the loaner homework I could get.
I will use Mr. Buddy this fall, but only to warm the trailer up before going to bed. The vent will be open and no heater on during the night. So I guess I will be ok. Other priorities prevent me from doing what you are before this fall; that is adding some other heat source. I will do that after hunting season this fall, during the winter months. With what I will go with, either hydronic or Platinum Cat, I should not add to the moisture issue.

[cornfused]

I did spend a few nights in my trailer in 5-20 deg F with the Mr Buddy. Condensation wasn't bad, nothing was really dripping except maybe the windows when the curtains were up. On the colder nights you could see where the tubes were in the walls because they had a light layer of frost on them. The windows would freeze over when they were down. I kept the buddy going all night on it's lowest setting. I had my roof vent open a hair and my lower vent open a hair too.

On the rare occurrence I was somewhere with electricity I used an electric space heater (1000-1500watt) with a thermostat on it and I didn't even notice any condensation with two sleeping in the trailer at night.

[lrrowe]

Then I should be in great shape for hunting camp this November. I am used to sleeping with temps as low as 20 degrees with two sleeping bags in a tent type setup with sweat pants and shirt and good pull down hat (maybe a hoodie if needed) with no heat. So until I get the "real" heating system installed, with an insulated CT, I should be ok. I will just yell over to the other hunter/campers to get up and light the Mr. Buddy at 4 AM.

I am going to think about a solution for the cold that comes through the uprights.

[hankaye]

Howdy All;

When I first got my trailer, Rascal (the dog), and I were on our way to Mont.
to do some fishin' with some friends. When I first arrived at the campground
my first priority was to cut a hole in the side for an electrical outlet so I could
power my Oxygen generator and so I could use an oil filled electric heater.
Between the 2 (O2 gen. does throw off some heat), Rascal and I stayed warm
when the night time temps. dipped into the 20's (F), Zero condensation ...
I kept the 2 overhead vents cracked a wee bit same as I do in the 5th wheel RV
we call 'Home". "Home" has a propane heater that's exhaust vents to the outside,
but, ... without the overhead vents cracked a bit we would get condensation in
it during the Cooler months. Just a matter (for me), to find the proper balance
to prevent the moisture build-up.
Not sure as yet, how I'm going to insulate the CT, thinking of using some 1/4"
X 1" screen trim to create an air space between the Blue Board insulation so it
can breath, kinda like they do for pole-barn roofs. Any thoughts about that idea???

hank

[MtnDon]

Howdy All;
Not sure as yet, how I'm going to insulate the CT, thinking of using some 1/4"
X 1" screen trim to create an air space between the Blue Board insulation so it
can breath, kinda like they do for pole-barn roofs. Any thoughts about that idea???

hank

Question: Where exactly is the air space envisioned? Between the rigid foam and the outer wall's aluminum skin? Where and how is it going to "breathe" in and out? That's easy in a barn or home roof, but I'm not sure how I'd do it in a wall system.

I think this is where the spray on closed cell foam excells. It seals the foam to the metal; no air space, no condensation. But it is not cheap and can be difficult to find someone who wants to deal with a small project like a CT. I never found anyone in the ABQ area would would even think about doing it.

I hope my method of "gluing the rigid foam sheet in place between the ribs with foam in a can proves to be sucessful in the long haul. So far, with the second layer of foam sheets glued in place over the wall plywood, the trailer has been snug and the only condensation has been on the single pane window.