Most bps will sacrifice thermoregulation for a good, secure hide. That is why I think it's so important to offer multiple hides that are identical. That way if you see them moving around it's because they are preferential to the temp and not the hide.

If you aren't using any kind of screen, then your best bet is to use a larger bowl for the water dish. The larger the surface area, the better. Put it on the hot side, and you should see an increase in your humidity. You are measuring with a digital hygrometer right? Don't go by those dial thingys. They stink. Good luck getting that humidity up. You should also see it increase, with the decreased usage of your home's heating.