I live in a VERY dry climate and humidity can be a major issue. If you mostly cover the top (see pic above) that helps. Also I have found that if I spray the aspen (with the spray bottle set to stream) to get the aspen wet then mix (like tossing a salad) and repeat that really heaps the humidity. I am just sure to do this in a couple of spots where the snake is not hanging out. You don't want the snake to be chillin on a wet substrate.