Some owners have a plastic sheeting around three sides of the enclosure...helps hold in humidity and heat from your heating source. Our temp drops some when misted, but recovers very quickly. (We have not added anything to the enclosure.)
Chams are not so delicate that a temporary drop in temp due to misting harms them. The temps in their native trees would fluctuate all the time due to wind, rain, sun movement, etc. If your cage provides a gradient of temps your cham can regulate itself by moving.