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Discussion Starter #1
We speak rather abstractly of this possibility. For a guy on the British self-build forum this morning (sbmcc.uk), it is not an abstraction:

"new man here, I am third way through transit conversion, got the kitchen unit done and 1 cupboard overhead, after winter standing I have mould come through where the screws are on the ceiling, I have insulated with a sheeps wool mixture so don't undersdtand how it is condensation, is there a fix thast doesn't mean stripping the ceiling down"
 

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And imagine opening the van door and smelling a musty damp sheep every time you get in...... Ewe.

Lesson for us:
His problem might be just that the screw head is cold and forming condensation due to being screwed into the rib. Clorox it off and pull down enough ceiling to see if the sheep is damp. It might not be.
It makes me think we might be better off to fasten the interior panels to the ribs (which are cold conducting materials difficult to insulate) with the plastic push pins or metal-into-plastic fasteners.
 

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We speak rather abstractly of this possibility. For a guy on the British self-build forum this morning (sbmcc.uk), it is not an abstraction:

"new man here, I am third way through transit conversion, got the kitchen unit done and 1 cupboard overhead, after winter standing I have mould come through where the screws are on the ceiling, I have insulated with a sheeps wool mixture so don't undersdtand how it is condensation, is there a fix thast doesn't mean stripping the ceiling down"
MsNomer,

Thank you for the heads up, very interesting.

I'm not sure how i'm going to do it yet but, I'm going to try to isolate my inner skin/structure/wall panels from the insulation and the insulation from the outer van ribs and skin.

Cheers
 

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And imagine opening the van door and smelling a musty damp sheep every time you get in...... Ewe.

Lesson for us:
His problem might be just that the screw head is cold and forming condensation due to being screwed into the rib. Clorox it off and pull down enough ceiling to see if the sheep is damp. It might not be.
It makes me think we might be better off to fasten the interior panels to the ribs (which are cold conducting materials difficult to insulate) with the plastic push pins or metal-into-plastic fasteners.
RDinNHandAZ,

Thank you for the thoughts.

I have been thinking about the materials that I can use to stop cold/heat bridging between my wall surface structure, but have not given much thought to the fasteners. I'll have to think on this.

Cheers
 

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2014 136” HR
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Discussion Starter #6
The amazing thing to me is that the van was not even being breathed in, much less cooked in. It's just been sitting, admittedly in a humid climate.

I think my 1" wood rib on the ceilings will address the issue, and there's wood behind my "crown mold" attachment. It will be harder lower down.
 

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The rib being separated by air space from the shell should help. I used a few cans of spray foam to fill mine, tedious but reasonably effective. Attached the ceiling with sheet metal screws straight to the ribs.
 

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Discussion Starter #8
"Attached the ceiling with sheet metal screws straight to the ribs."

Apparently, that is the essence of thermal bridging. Direct conduction between outside cold and head of screw exposed to warm moist inside air. So, have you had any issues in humid winter conditions?
 

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No, but haven't had on the road and occupied yet. I'm not worried though, because I did a good job of foaming behind the ribs.
 

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I'm not at the point of attaching panels yet but have been thinking of how I want to do this. I hadn't considered bridging bit now as I toss that into the mix I'm leaning towards attaching 1" strips to the ribs and then screwing the panels into those.
Would I be correct that should prevent this issue?
Are there any reasons I shouldn't do this? The only reason I could think of was head height but that shouldn't be an issue.
 

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No, but haven't had on the road and occupied yet. I'm not worried though, because I did a good job of foaming behind the ribs.
You may have done all you can w/o separating the interior from the ribs with an insulating layer and eliminate the metal fasteners. I doubt he conduction of the ribs will be lessened by the insulation you put inside them and they are likely to be colder once insulated because there is less heat near them to warm them up. If it works you have the answer. I would think an insulating layer to isolate the ribs from the interior finish of the highest R value one could find and a nonmetallic fastener holding the assembly to the ribs would be best. A half inch of rigid polyisocyanurate would be enough and some sort of 1 inch plastic screws or pins or plugs to hold it all to the ribs would be ideal. The fact we know of one van that has the condensation and inevitable mold problem is unsettling. Let us know if yours seems ok. If not some retro fit might help.
 

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Discussion Starter #12
Bconno, check out my build--I did just that. Once you get the template for the arch, everything goes very smoothly. It made transition to the walls much easier. One of the best decisions I've made so far.

I confess, though, that I've screwed directly into the walls. I figure a problem there would be much easier to remedy.
 

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Thanks MsNomer, I'll check yours out.
I've never had any success using sheet metal screws on something that moves or vibrates, almost guaranteed to come loose quickly so looking for other options, rib nuts are sounding best for now. I have lots of time to change my mind
 
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