I have a few exo terra terrestrials set up for snakes at the moment. The way I set them up is I wrapped the sides and back with reflectix/bubblewrap insulation, had a piece of glass cut to fit the top (if you do this, make sure to measure inside of the tabs, otherwise the glass won't fit), drilled the top and mounted a radiant heat panel to the top glass. With this setup I am able to keep the enclosure nice and warm and not have issues with humidity loss.