Looking for an attic ladder for outdoor use - tips?

You're messing up. Install an insulated attic ladder of a brand-name make, like dolle Bremen for example, and no worries, no mold. Or like we did, a real door, we took a patio door. With double glazing. Now the cat always sits in front of it and looks at the floor, only she is not allowed up there, otherwise she might pee on the insulation wool.

Since our attic is not "heated along" in that respect, mold problems can certainly occur. I really know many (also newer) houses where mold grows there.

So you have insulation on the top floor ceiling, but not under the slope? (because if you have it there too, it would already relativize the "climate difference") - and I would say, not "also", but "especially" in newer houses this problem occurs. But not dramatically, and above all: controllable by ventilation.

As you planned it, the attic has the thrill of a smuggler’s hideout, and the kids then have to go through the bedroom to get to their "treehouse" ;-)

So despite the harmlessness of a limited warranty folding ladder, it would be too much hassle for me just because of a bit of mold phobia. Is your partner a difficult co-driver on Friday the 13th? :-)