I already replied that smae solution to the other thread. Not sure why you made 2 threads. Have a mod delete one.
It encloses the cage, that will keep the water from drying up as quickly.
When you say, its at 20% when? It does not need to be constantly high all day long (depending on your species of cham). You just need spikes of highs then dry out in between.
I would do your best to save up for a Mister. The chameleons cage needs to be misted multiple times per day. If you have a job or go to school, in the day you will not be able to maintain that. Furthermore you wont want to soon.