The room is about 350 sq ft big. No stove top for boiling water/steam generation. Tried a humidifier but I need a fairly big humidifier to alter RH level equilibrated to a consistent 45-50% or so. We have no green thumbs but may be running out of alternatives, and seriously considering adding and maintaining hard to kill plants to keep up moisture level. From your experience, what plants do you have effectively bump up humidity in a dry winter?