Hi,For years people have try-ed to accomplish this. Here is a simple method depending on size of tank that will work. Place a suitable size container of glass filled with water and insert an aquarium heater which you can get in different lengths and wattages into the glass container inside the tank, adjust the dial to the desired temperature. The temp from the glass container filled with the heater and water will increase the humidity and temp level of the tank making it warm and humid. adjust ventilation accordingly. Hope this helps.
Regards