If you are doing a small green house, think about a small fan to keep the air moving and the temperature even. I had a very sad 1st year with the DW small greenhouse. Some nice person took pity on me and told me to add a small fan to move the air around, IT WORKED! Just a thought. Hoping all works for the best for you!They work in fall too, if the weather is a couple degrees below freezing. Just enough to take the edge off.
Scott