From Here

So now you have a wooden framework with glass panels installed. Where do we go from here? This design is intended for you to figure out how to enclose the space and help you grow vegetables when it is cold outside.  A lot of the finishing steps will depend on what you have to work with.

  • Roof. On my first version of this greenhouse, I used cement board / hardiebacker board for the roof. The joints with the frame were caulked. This seemed like a good (15 year) solution. Also plywood, tarpaper, and shingles (which I did not get from craigslist) might be possible. In our area, large mirrors and doors can be free on craigslist.
  • Back and side walls. In my experimental greenhouse I used particle board for the back wall and sides, and painted them. The moisture caused the boards to warp, so I would recommend something sturdier, even if you have to paint it. For the greenhouse shown here, I am thinking about using cement board, then piling dirt against it, maybe 4 feet high
  • Dig walkway. This step is essential to a) get the dirt to build up the bed by the south glass, and b) drop the working area so it is easy to walk inside. Since I have not done it yet I’ve included a photo below of how the dugout walkway looks in my experimental structure.  The dirt dug out is put right in front of the pathway to raise the seed bed higher to be close to the front panels.
  • Front of structure, below the panels. The gap between the foundation and the lower part of the frame – that will be filled with dirt from the dug out walkway. That could be closed off with cement board.
  • Insulation. I did insulate my experimental greenhouse and will insulate this one under construction. Also will add a couple 55 gallon drums to hold water, and heat up during the day, and release heat at night. There were 2 nights last winter when water inside the greenhouse froze.