Pretty nice setup you got there. I took the easy route this spring and bought a low tunnel plastic greenhouse. I have had a couple of 4 rack, 20x20 towers for 5 years or more. But they aren't good in the wind and I wanted something lower with more surface area for full light for everything rather than racks, and for more ground heat retention. It is just a little...9x3 footprint on a raised bed, and I put cinderblocks and buckets of water inside to help regulate the temp. But on a hot day, it will get hot, and needs to be unzipped. And I had to use lead ingots all around the "skirt" of the plastic, just to hold it down.

With some heat from light bulbs overnight, I am good am for a few degrees below freezing, but it is certainly not ideal. Maybe next I invest a little more time into building something from scratch. I'd like the top window to angle south, but we don't have a great southern exposure anyway unless I put it in the front yard.