With those low ambient room temps you will definitely need to make some modifications to the tub. Either 2 heat pads on thermostats as advised, or cutting a hole in the lid and using mesh/wire screen and some type of edge protector with a low wattage heat lamp or CHE. There are some tutorials online on how to do this. You could also increase the room temp.

With that said, it's usually just as easy to make modifications to glass tanks to hold humidity as it is to ensure ambient temps in a tub. Using a good substrate, covering the lid, covering sides with insulation, making humid hide, using a damp towel, etc. are all possible ideas.