I decided that my current 11×22 back patio will become my new greenhouse and hold my water cistern at one end. The greenhouse will keep the cistern water from freezing in my zone 5 winters. The cistern water will moderate the greenhouse temperature, absorbing heat during the day and letting off heat at night.
The entrance will be straight from the garage into the north end of the greenhouse, keeping it more secure for night access and preventing excessive heat loss from an outside door.
The side walls are already dry stacked and will be coated with fiber cement. They are 40 inches tall and I will affix a lightweight A-frame on top, covered with opaque white roofing panels because they diffuse light better.
The boards will be 8 feet long and the plastic is also in 8 foot sheets.
Perhaps I can grow worms inside the beds, in the warmer temperatures.
This will set me up for water security at my home, since I am looking at about 750 gallon storage capacity.
I will have another water storage adjacent to the shed, with a 150 gallon water storage. I doubt it will get more than 1300 gallons per year. I already have the parts for this setup and now that I am retired (and bought a bigger utility cart) I will likely get this one in by next summer.