Aluminum frame condensation leading to other probs?

[chris_the_wrench]

I'm continuing to formulate my next camper, and hopefully getting close to finalizing the design. One question that crept into my head recently is:

On aluminum framed campers that have an exterior fiberglass or aluminum skin and then some kind of wood or luan interior wall, when they are used in cold(-0 F or really any cold temps) condensation develops on any and all exposed aluminum surfaces. Is this true of the "hidden" aluminum frames? If so does this collection of condensation in a relatively tight space(between exterior and interior walls) lead to issues such as mold or rotting the interior wood paneling when the camper returns to non-freezing temps?

Are vapor barriers employed?

In addition, does FWC(or others) coat their aluminum frames with anything or are they just bare aluminum?

Thanks
-Chris

 

[Pest]

Yes, condensation will form on exposed aluminum as well as on the portions of the wall (inside the living space of the camper) covering the aluminum if there is no insulation in between. I would say that typically there is not a lot of empty space between the wall and aluminum (usually a barrier of glue or something) for much moisture to build up in. Potentially, there could be a problem though. The key is to air out the camper as soon as you can and let it dry thoroughly, warm or cold weather. It will generally take at least a few days for mold or anything to grow if not vented.

To my knowledge, vapor barriers are not used, but I could be wrong.

Don't think the aluminum is coated, it wont rust.

 

[Treenail]

My 'expo' camper is like this:

http://stonerradiator.com/images/dsc00667.jpg

The walls are FRP. The ceiling is aluminum sheeting with hollow aluminum 'rafters'. When it is time to start insulating I'm going to use the small cans of spray foam insulation to fill the rafters and hollows in the corner extrusions. This will reduce the thermal bridging as much as possible. Next, I'm going to fit foam sheeting that is the same thickness as the rafters in the ceiling. Adhesive will hold the sheets up.

I just read a post by a guy who rebuilds old, 60+ years, aircraft style trailers. Scroll down a few posts:

http://www.expeditionportal.com/forum/threads/71773-Any-camper-builds-using-T-Slotted-Aluminum

My plan is to add a second layer of insulation with the joints running perpendicular to the first. Then a vapor barrier followed by plastic sheeting for the inner paneling. right now I haven't decided how I'm going to attach the sheeting to the 'rafters'. Using industrial double face tape is tempting. That, or adhesives again. There would be no metal to metal bridging. On my '82 E250 frost rosettes would grow any time I camped below about 10f. Small worry though...the cheap house paneling I used never deteriorated after 245k miles of use.

Tom