Temperature depends the type of plants and the desired yield.
In general, I'd set the minimum temperature to 50 o F at night. During the day it should get warmer and you may have to vent a little to keep the greenhouse from over heating. Here's a basic outline of plant hardiness, these are the minimum temperatures and not recommended for growing. Hawaii 40 o F and above Orchids, Begonias, African Violets, Bromeliads, Heliconia, Some palms, Pineapple, some citrus. Greenhouses by Ortho Books has sections on managing your greenhouse and using your greenhouse.