Anyone else experiencing mildew under a completely sealed vent???

[burtont123]

I have a 2010 Jayco 1207 with two vents; a powered fan vent toward the front and a static vent toward the rear. A few years ago I noticed mildew developing on the canvas that lies directly under the powered vent when the camper is folded down. There is no mildew anywhere else (I am diligent about keeping the camper dry and spotless). Initially, I thought the vent must be leaking though I have never seen or experienced it leaking. I had the vent sealed. Yet, again I noticed mildew forming in the same area. I know that the vent is not leaking because we have slept in it during monsoons and it was completely dry. I have opened it after a hard rain to see if there was any moisture and there is none. I assume that the mildew is created by condensation forming under the plastic of the vent on sunny days and then dripping through the screen onto the canvas. That is only an assumption. I am wondering if any other owners are experiencing the same thing?

[Threebutchers]

My guess is that your vent is not as "sealed" as you think it is....the heating and cooling of the camper / expansion and contraction creates airflow - and therefore condensation (and mold) at a point where competing temperature and humidity occurs. The following video will explain....

http://www.youtube.com/watch?v=kCkDM5uC7ec