Not an expert, but i think thats going to be tough for you. The size is small so it will not hold its heat as long as a larger greenhouse plus even if you have the majority of your winter temps in the 20's-30's its gonna take alot of energy to heat even that small space. I personally would look into getting a small air forced heater like the ones used in small trailers and campers. They run off propane or fuel oil and are quite energy efficient. Electric baseboard all the way around the base of the greenhouse would probably work too but may be expensive in the long run.