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Window Condensation

8284 Views 27 Replies 6 Participants Last post by  cargovanconversion
I'm preparing to work on the walls of the van, and I have to prevent, that condensation from my 'All-Around Windows' has the opportunity to get into my insulation.

I noticed that at some points, water can seep into the walls underneath where there are no weeping holes.

General question: How is your experience with condensation on the windows?

Specific question: What have you done to keep that wall space underneath the windows dry?

I thought of gluing insulation board against the skin of the vehicle, but now wonder if I shouldn't use an airspace first.

Van Williams
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I just bought a small Eva-Dry model EDV-1100 dehumidifier for $48.00. For an additional $13.00 I will buy the optional 12 volt DC power cord. Will see how that works to reduce or eliminate the condensation inside the van. We will see. Sticker on unit says 2.5 amps @ 9 volts DC.
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I take that the above means that you have a condensation problem? And if so, how does it manifest itself and what is causing it?

Van Williams
In the mornings occasionally I have had moisture on the inside of the glass and some metal parts that are not insulated. I assume that that condition occurs when it is warm during the day and it gets cold at night. As the interior air of the van cools toward the exterior temperature it gets past the dew point and the moisture comes out against the cold parts. People also produce moisture when they sleep. I do not run a heater at night to keep the van temperature high. I use a 12 volt heating pad under the sleeping bag to stay warm.

Suspect the small dehumidifier will eliminate the condensation. I will let you know how well it works next winter.

If you have locations where the interior air contacts the cold van steel, you can get condensation even if you can not see those locations.
Most of what you describe will likely happen in very RV. But I wonder, if you have seen that window condensation drip into the wall and collect at the bottom.

Van Williams

I did see a new van on the Ford lot with about 2" of standing water in one of the lower cavities. I also could not find drain holes in my van. I used sealant on all the black trim fastening holes/fasteners on the inside before I insulated and closed up the openings with panels.
My approach was to eliminate air pockets against the van steel as much as possible. No air contact means no moisture condensation.

Window indents have polyiso glued to the steel and the voids filled with Great Stuff. Lower and upper deep wall sections have two layers of 1" Aerocel closed cell foam glued to van wall and each other. Then a layer of Reflectix on the closed cell foam, a 2" air gap to the 1/4" plywood wall covering. The ceiling is filled with polyiso with gaps and ribs filled with Great Stuff. A layer of Reflectix on the polyiso, an air gap to a layer of thin white Thnsulate that sits on top of the Macrolux polycarbonate twin wall greenhouse ceiling panels.
Maybe the solution is to deal with the problem and not the end result. Either air circulation or the use of a dehumidifier could reduce the moisture content of the interior air. Another approach would be to keep the interior air at a high enough temperature to be above the dew point. Or some combination of these.

I am hoping the small dehumidifier will reduce the moisture content enough that I do not have to heat the whole van or replace the warm interior air with colder outside lower humidity air. Will do some experiments next winter to determine what will work and what will not.
avoid placing any insulation against the skin of the vehicle, but use an airspace first, followed by poly-iso and a flexible insulation such as thinsulate or denim.
From what I have read it is not recommended to use demim insulation. It is hygoscopic so it will hold the moisture.
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