Condensation help

[Dcregger]

Hello All !! I'm just at the beginning of the build inside. I'm wanting to see what will be the best thing to do to stop the condensation problems? Is there something you can paint on the walls and ceiling ?

 

[Rucker]

Thanks for putting in your bus information! Makes it easier for others to provide input.

If you search 'condensation' in the little search box in the upper right of the forum you'll get at least four hits that pretty well cover causes and solutions of condensation.

Pretty straightforward: no matter what the surface, metal, paint, foam insulation, if that material's surface temperature is below the dew point of the air inside the bus the water vapor will condense out.

a) keep the interior air moisture content low by not using propane heaters;
b) Insulate and provide thermal breaks between the exterior surface of the bus and the interior surfaces;
c) Avoid extremes of temperature by chasing 70 degrees.
d) Read those other threads you find via search. There's a helluva lot more detail on this topic there.

 

[Dcregger]

Thanks for the info!! I will check it out!

 

[DeMac]

You have an IC RE school bus. Our buses have a void above each window (1.25"dia X 24") where convection occurs with both interior & exterior currents.

Air currents pass through, over each these gaps. I've documented my solution (CCBR) in thread or two. Recently here
Subzero-Yeti Window-Convection.

The link is to my post & pictures, but the whole thread is a good read. There's practical, real-world experience, throughout.

 

[Dbacks2k4]

Hello All !! I'm just at the beginning of the build inside. I'm wanting to see what will be the best thing to do to stop the condensation problems? Is there something you can paint on the walls and ceiling ?

You need what's known as a moisture barrier between the external metal skin of the bus and your inside. One of the reasons spray foam is so popular is that in addition to providing insulation it also serves as a moisture barrier. If using other forms of insulation you'll need a corresponding barrier installed.

Other good tips are:
Avoid using propane heat sources which generate a lot of moisture.
Have good ventilation in place, especially near the shower.
Make sure if you're leaving the windows in that you have a mechanism to drain condensation from the windows so it doesn't leak in your walls. RV windows have a "weeping hole" for that moisture to drain out of, school bus windows do not.

 

[DeMac]

Details?

You need what's known as a moisture barrier between the external metal skin of the bus and your inside. One of the reasons spray foam is so popular is that in addition to providing insulation it also serves as a moisture barrier. If using other forms of insulation you'll need a corresponding barrier installed.

Other good tips are:
Avoid using propane heat sources which generate a lot of moisture.
Have good ventilation in place, especially near the shower.
Make sure if you're leaving the windows in that you have a mechanism to drain condensation from the windows so it doesn't leak in your walls. RV windows have a "weeping hole" for that moisture to drain out of, school bus windows do not.

All great info. Sounds like a good plan, Dbacks.

U, me & OP have the same type of IC. Please post photos of the weepholes you describe, so we may learn from your experience & the mechanism you used.

 

[Dbacks2k4]

Here's a good video about the weep hole on RV windows.

I'm not replacing my school bus windows, just re-sealing them. I'm in the process of taking them out now. I'm not sure how I'm going to solve the problem yet. Assuming I can't simply drill my own weep holes into them, I'll probably just create a type of gutter system with my walls

 

[Ozbozz57]

I read here where a number of people say "don't use propane heat".
It's as incomplete a statement as saying "heat rises".
Burning propane DOES produce moisture. A considerable amount.
Frankly, so does breathing.
Where the byproducts of propane combustion go determines whether the moisture is inside your bus, or outside of it.
UNVENTED propane combustion releases the moisture and everything else, possibly even carbon monoxide, into the interior of your living space. You should keep this combustion to a minimum. I make an exception for propane cooking, since a cooktop burner is fairly small, and is not used for very long at a time.
VENTED propane heaters release those products to the outdoors.
VENTED propane heaters produce dry heat.
Rucker is dead right about the dew point.
Showers, cooking, and washing dishes are pretty much unavoidable moisture sources. Make sure you have a way to vent that out.
Insulate well, use thermal breaks, provide a vapor barrier on the inside (warm side) of the insulation envelope, don't produce excessive moisture.
Do all that and you won't have a condensation problem.