bret,I built a greenhouse using polycarbonate panels on top and old sliding glass doors.I took the glass out of the doorframes and used 4x4s as the way to frame them in.Also used some large double pane storm windows that I can open in the summer for ventalition. I heat it in the winter with a combination of propane solid state ingition furnace,wood stove and two4x8' passive solar panels that I made.I built it on the south side of my barn.I also used concrete as a floor which also acts as a way to store the days heat.on a cold day it can easily get in the 90s with just the wood stove and the sun ,the propane is usually needed at night and only for short periods. It works pretty good as I have tropicals that are as old as the greenhouse which I built 7yrs ago. russ