Herp room help

[Mchristy]

I am using a room off my garage as a herp room until I can afford a separate building. The room is fairly small, 7x15 (105 square feet) and is build directly onto the slab of concrete the garage is on. I know for sure two of the walls (the walls facing outside) are properly insulated but the two walls facing the rest of the garage may not be. I do not have the ability to properly insulate these walls if this is the case. The room runs off of one 20 amp circuit and does not have heat installed at this time. Also, the breaker box for the house as well as the giant box thing for our solar is in this room. I am having an electrician over tomorrow to see how much it would cost to increase size of the circuit in the room and I am also going to get an estimate on how much it would cost to add hot water heat and a thermostat into the room for heating. Lastly, the room has little to no ventilation whatsoever. No windows, one door, no vents for heat or cooling. Just a rectangular room with one door. My question is, what else should I do to ensure proper conditions for my animals? Do I need to add any ventilation or will no ventilation help keep in heat and humidity? currently I have a relatively small collection of balls and boas but I do plan on expanding. Any insight would be invaluable to me.

[Annarose15]

Pictures would help, as well as information on how hot/cool the room gets naturally. With that size room, my bet is you only need an oil-filled radiator heater, not a water heater installation.