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Full Version: Question about condensation and insulation if any one knows
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Hey all, I took the rubber mat and whatever kind of insulation was under it out. The insulation was slightly damp but my floors were in pretty good shape. It had holes from some previous installed stuff so I patched them with some fiberglass stuff called kitty hair. Then painted the whole floor with Glidden Porch and Floor paint just for good measure and that worked great.

I put down 1/2 inch GAF polysio and will cover with 3/4 inch plywood because that's what I already have.

Finally my question is do Chevy Express cargo vans have any kind of drain holes along the inside walls that I should not cover up?

I know that under the side door step well has drainage holes.

If there are no holes to worry about in the cargo area I could tighten up around the edges of the Polysio insulation with some type of caulk.

Does anyone know? Thanks
I hope you will get some responses to your post. I read a lot of the insulation posts here and elsewhere and I ended up kind of picking and choosing what to do for my ford van, but I will say I did a lot of head scratching wondering if it was right or wrong LOL.

As yet I haven't been in cold weather, so I don't know how my insulating job will fare with the difference in outside/inside temps and am curious what others have found from their own experiences. Some say no insulation at all is best, some say lots is best, so I dunno...

Here's what I did that I hope will work: 1 to 2 inches of polyiso on the walls that I sealed with silver tape, vinyl finish wall covering, similar floor to yours with vapor barrier over the plywood and a finish floor, holes in platform so mattress can breathe, and adequate ventilation. My van already had an insulated high-top so I didn't have to do anything to that.

I just hope I don't have to go in between the inner and outer walls and rip out all the reflectix I slid in there! When I tested doing that it seemed to help cool down the inner walls and door frames right away so I just kept at it until I got about every nook and cranny but I did make sure (I hope) any moisture could drain down and out through those weep holes.
Those mystery wiping holes is what kept me from using expanding close cell foam on the van ribs. So I just stuff some with pink foam and some with Reflectix. We'll see what happens this winter.
I can not find any drainage holes along the walls in the cargo area. I think I will only insulate the roof now for this winter and see how that goes.

Making the decision this weekend if I will spend needed money on Foam it Green . . . this or just go with the Polysio because I need the money for Solar.

If I just do the roof that should keep the condensation drips off my bed I hope.
Good subject and one I've researched extensively and one I'm currently dealing with in a big way with rust repair from plugged drain holes.

Thing is, the more I search the more I see conflicting info regarding insulation type, condensation in a metal box and rusting, vapor barriers and where to place them, etc. I think it matters hugely what climate type you're insulating against.
@AltTransBikes, yes, I agree. The argument for no insulation gains footage when there are so many variables that could change up the recipe, but I chose to insulate and will see my results from experience.

@A Seeker, I stayed away from foam spray insulation as I read from many that in contact with metal, it corrodes.

Also I stayed away from fiberglass batts as they collect moisture. I found evidence of that when I pulled off the back door panels to see what was in there - yep, cruddy fiberglass batts but thankfully no rust. I cleaned and dried it all out, slid in reflectix loosely and vertically and some polyiso (leaving weep holes at bottom to function), then taped reflectix across all the door frame holes and/or taped them with silver tape, then replaced the panels.

I am hoping the silver layer on the polyiso, combined with a lot silver tape will be an adequate 'vapor barrier' for the walls.

My van was clean and rust-free, so I am pretty sure the weep holes aren't plugged but sure enough, I didn't actually check and I'm not sure I'd know how to get at the ones down at the bottom of that inner wall area anyway except maybe with an air compressor and a vacuum wand or something. I can't see how they would become plugged now that the walls are in. Something like road grime would have to happen from underneath for them to plug up now, I think (hope).

I'm hoping what I end up with once I finish* is an interior space sealed from the metal but with plenty of ventilation through a dc fan and window cracks fore and aft.

* Still have to address the ridge where the roof ends and the hightop begins.

Good luck this weekend!!!
Hi sassypickins, I to have read about the foam causing rust. I think it usually was with Great Stuff foam that is open cell foam and not water vapor proof.

I am no insulation expert for sure but my understanding is warm moist air has to reach a cooler surface for condensation to occur.

I think with the closed cell foam will not let the moisture through so it is completely sealed and does not have the condensation between it and the metal. It is not inexpensive though and probably a learning curve to applying.

I am still probably doing polysio sheets like I put under my plywood floor as it is a lot cheaper.
Thanks for the warning though
yqw. You sound prepared! It will be a while before I know how well it all works, but I'm going try to remember (ha!) to post results down the road.
Something I'm very curious about: I see a lot of van projects where the somewhat natural tendency is to pack/glue insulation tight against the metal skin of the rig....bubble wrap, expanding foam, foam board, etc....if anyone ever has or had occasion to peel it back after a good trial time and found it rusting the metal.