Yes, keeping the humidity up in a screened enclosure is a challenge, But a screen enclosure is a must from what i've researched. They need air circulation to prevent respiratory problems and above all, They do not need to be seeing their reflection that glass sides would show. If they see their reflection, They will think it is another cham and they will try to attack and hit the glass or they will simply be stressed all the time. I keep the humidity in by wrapping the sides with "Landscaping fabric" or cloth. It is a cloth made up of nylon fabric that will help hold the moisture in and let air circulate at the same time. It is also colored black, so he can't see through it to other enclosures containing herps that might irritate him. I also have live potted plants on the floor of the cage. I keep a water dropper on top that drips down to the plants. I also mist the cage with a bottle sprayer. Chams are a look but do not touch sort of animal. Especially when they are mature.