Why all manufacturers do not use composite?

Gdetrailer wrote:


X2!

Another potential "pitfall" of materials like "Azdel" is the fact that if it is "water proof" it can HOLD water in between the walls..

Essentially TRAPPING moisture which will eventually MOLD AND MILDEW..

Then you are no better off than using good old time proven stick and tin..

So if you are looking at the idea of Azdel as curing all water leak problems you are only kidding yourself..

Good point. But there is still an impervious layer on the outside of all RVs that is essentially on the wrong side of an exterior wall assembly. Moisture laden air can migrate to exterior walls where it will condense on the exterior skin in cold weather. This is a fundamental flaw of RV construction IMO. In buildings, the vapor barrier is on the interior side of a wall so that moisture is kept out of the wall cavity. Same thing in ceilings.

If you use an RV a lot in the winter and fail to ventilate it adequately, you WILL get moisture condensing on the exterior skin and underside of a roof.

I doubt Azdel will help with moisture control and may make it worse due to lack of ventilation in the wall cavity. An improperly built shower in a house with an exterior wall can end up with the drywall turning to mush for the same reason of trapping moisture between two impervious layers.