Humidity is always a balancing act between moisture and ventilation, if I'm adding moss to make a humid hide I do it inside a tupperware container with a hole cut in for access.
What state is the old enclosure actually in?
Depending on what it is constructed from we might be able to give advice.
It is a wooden cage with plexiglass front view and mesh ventilation on two sides and lid. Currently there are spots of mold spread along the bottom and the bottom has turned black and soggy.