It is possible to keep the humidity up in a glass tank. You just have to be creative and vigilant. Because my house is extremely cold, I do have to have a heat lamp run 24/7 to keep ambient temps up, as well as two separate UTH on their own thermostats to keep the current belly heat temps. So this dries things up even more. I finally got mine sorted out by covering the screen lid with foil to start with. I've insulated three sides of the tank with insulation foam. I have two water bowls in the tank to have more water surface area. I use newspaper for substrate since I did not have luck with coconut coir - turns out it makes me break out into hives. Yay random allergies. I also have sphagnum moss that dampen once a day in the tank, as well as a third water bowl that I keep a damp wash cloth spread out over. I pick out the soiled moss and toss it and replace it. The washcloth gets washed. She's yet to soil the washcloth, but I bought a bunch of them so if it does, I'll just toss any that do.

Doing this gets my humidity up to 60% pretty quickly, I dampen everything before bed, and it lasts throughout the night and next day until I dampen again.