What’s up with the mildew inside new coop?

[Duck Hill]

I live in the south and the moisture is enough that not only do my closets get mold, so does the plastic siding on the outside of my house. I treat both with bleach. Only my duck house, with the extra ventilation, is mold-free. Oh, and the crawl space is also mold-free, because I leave a large fan running continuously during spring, summer and fall to move the air around. That would be another option for your chicken coop - a continuously running fan.

 

[aart]

The coops on the other side of the run aren’t right up near the woods like this one.

Tht could be key.
My back patio slab, north and two story side of walk out, gets some kind of black growth on it, every couple years I have to power wash it when it gets slippery.