The inside of my bus is wet!

[Iheartbus]

We had a string of super humid days and then a few rainstorms. The bus has no leaks...but it is unbelievably damp inside in the mornings!! Moisture is everywhere, it's gross! What can be done to reduce this? I am worried about doing any remodeling and having moisture build up afterwards.

Thoughts?

[oricha1984]

http://www.skoolie.net/forums/f13/co...bus-12538.html

http://www.skoolie.net/forums/f13/co...bus-16035.html

[Njsurf73]

I was contemplating a dehumidifier when it's parked. Keep it dry and mildew free.

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[Robin97396]

That's humidity from your own breath you're seeing on the walls. If you've still got a top hatch in your bus try putting a wood spoon between the hatch and the bus to hold one edge of the hatch open just a crack. It lets the humidity escape slowly during the night.

[Njsurf73]

I didn't​ think about that. I was assuming it was humid warm air being cooled overnight and condensating

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[EastCoastCB]

Originally Posted by Iheartbus

We had a string of super humid days and then a few rainstorms. The bus has no leaks...but it is unbelievably damp inside in the mornings!! Moisture is everywhere, it's gross! What can be done to reduce this? I am worried about doing any remodeling and having moisture build up afterwards.

Thoughts?

Buses sweat profusely. Why I'm so perplexed that they're stuffed with fiberglass!

[Iheartbus]

Originally Posted by Robin97396

That's humidity from your own breath you're seeing on the walls. If you've still got a top hatch in your bus try putting a wood spoon between the hatch and the bus to hold one edge of the hatch open just a crack. It lets the humidity escape slowly during the night.

Lol this was beyond what my own breath is capable of.

The rubber floor was extremely wet, very few spots were dry, it was extremely humid inside likely from the extreme weather we had, I'm just wondering if insulation will stop that from happening. I might just take out all the windows if it's gonna sweat like this, was quite shocking.

[Robin97396]

Ok, but it won't cost you anything to try the wooden spoon in the top hatch. It may not fix it but it should make a difference.

For me the insulation made the condensation virtually unnoticeable, but yes the windows still sweat if there's a temperature variation between outside and inside. I'm very fond of the insulated panels I put in the windows, for reducing condensation and for privacy at night.

[Marceps]

The bus has no leaks.

What makes you so sure? Do your ceilings not have insulation? A hairline crack, allowing but a single drop of rainwater beneath its surface every ten seconds, produces the very circumstances you describe.

[Iheartbus]

Originally Posted by Marceps

What makes you so sure? Do your ceilings not have insulation? A hairline crack, allowing but a single drop of rainwater beneath its surface every ten seconds, produces the very circumstances you describe.

No I dont have a hairline crack, we just had extreme weather conditions where it was very hot and humid. It's been a few days since and even though it's been rainy it hasn't happened again. My guess is the bus just got too hot. I'm hoping insulation will reduce this sweating of the metal.

[family wagon]

Night sky radiative cooling can produce astounding results. I wouldn't be surprised if Njsurf73 has hit the nail right on the head: during the day the bus is filled with warm humid air, then a few hours after sundown the bus shell cools very rapidly due to NSRC. The air inside doesn't cool so fast though, and it still has a pretty high moisture burden, so it isn't long before the metal bus surfaces cool below the dew point of that warm wet air and condensation begins. It'll fall like rain drops from anywhere on the ceiling as well as run down the walls.

Do you have some kind of sports/action camera like a GoPro? Set it up for time-lapse photo mode with a power supply and a low-heat lamp and let it run overnight. If the condensate theory is correct you'll be able to watch it form in the photos.

We've got to confirm the source of the water before we can suggest appropriate mitigations.

[family wagon]

Oops. I just re-read your post #10 indicating that this hasn't happened again. That does make it harder to test and prove the origin.

If you're willing to assume it's a warm air condensation problem then there are basically two solutions. One is to get rid of the water while it's still in vapor form, ie use ventilation so that the air inside cools along with the air outside. The other is to keep the humid air away from cold surfaces to prevent condensation, ie use insulation and vapor barrier. That could be an insulation with high vapor permeability plus a separate barrier (fiberglass batts with kraft or foil facing, or a layer of polyethylene film) or an insulation with low vapor permeability like closed-cell foam (spray or board with taped seams). Those are but two of the many options in the world of insulation.

[Iheartbus]

I was planning on just going full spray foam so I wouldn't need a stupid vapor barrier, we will see.

It was definitely super duper crazy wtf hot last week. I did have the windows opened (4 windows, at the highest latch setting so barely an inch) because of stupid bugs, and the top latch open and a fan blowing. It was still super gross hot in the bus even at night. Was so nasty wet in the morning. I'll try a dehumidifier on super hot days but hopefully I'll just have an a/c unit in here eventually and some better insulation than stock.

[Robin97396]

Even a week air conditioner does a pretty good job of dehumidifying the air.