Raleigh, NC here. Warm, bright sun and humid. However, not quite FL or Houston.Most trailers and boats in our area are stored outside in the sun. After a few years they look pretty aged.
We store ours in covered parking. The nose faces east and is open to the morning sun but the other 3 sides are enclosed.
We had our popup covered outside for several years and the covers failed regularly. It was awful. The few months in the open without a cover totally bleached the paint and decals.
We haven't had the Roo long enough to know the effects of the sun on the fiberglass front cap or decals but I do keep it waxed every few months. It was stored on a lot in OH for several months and I can see how the rear bunk latches faded. Bugs me bad.
So, we decided to keep this one under cover as long as we could afford. For reference, in our area covered on concrete is $150/mo and higher. Uncovered on dirt is $65+. Indoor back in with roll up door, not climate controlled, is $350/mo+. On the plus side, the covered spot we have is 5 min from home and has 120V electric and lights. If/when it does go outside, it will have a cover which I expect would have to be replaced annually.
Indoor, fully enclosed should be fine for moisture. I'm surprised by the mold issue if they used Damprid, etc and didn't put it away wet.
2019 Rockwood Roo 23BDS
2015 Yukon XL 4x4 5.3 Max Trailering package
2005 Fleetwood Valor (Sun Valley) Sold but not forgotten