Depending on how cold it gets, you're probably going to want some insulation. Styro sheets are very inexpensive. It's unlikely you're going to need a humidifier, but a dehumidifier may be necessary (transpiration can release quite a lot of moisture into the air).
If you're going to need extra heat, I personally am of the mind that it may as well give some light, too. When I needed heat, I added a light. Slightly less to half the wattage of a space heater. Or! If you can't spend the money, make an Electric Blanket Sandwich. I use them all the time.