I built a homemade GH on my backyard (under covered patio) using clear PVC roofing sheets from the Home Depot see attached photos. Just completed the project last month. Dimensions : 12'x4'x10'. My Primary purpose is to store tropical plants over the winter typically during the month of January and Febrary. I live in Dallas, TX and the winter is very short but it is cold enough to kill sensitive tropical plants if left outdoor without protection. Looking at the photos, can somebody recommend me what kind of heating requirement should I need? I already wired 110v power source to it should only small electric space heater is needed.

Thanks in advance,

Jimmy