The best thing that I have found for humidity, with a screen top, is keep 80% of the screen covered in saran wrap and place a damp wash cloth in the cage. I wring it out, re-wet it and place it back in the cage every day in a different spot as to avoid mold. However, if I leave for several days it is fine (stays damp) and the cage stays between 55% and 60% humidity. For shed, I don't wring it out as much and I cover another 10% of the top with another damp wash cloth or paper towel. Doing this I can keep the cage at a consistent 70% humidity for 2-3 days with minimal maintenance during shed. I would highly suggest this!