The greenhouse is officially ordered.
After some careful comparisons of the footprints of each unit (heating and cooling) as well as the enormous cost of running a gas line from the street to the back yard, we have decided to go with a mini-split A/C heating unit. This also means that we don't have to have any exhaust fans or vents. This means extra quiet, fewer bugs, and fewer cut holes in the poly.
We already have a 60 amp dedicated service on our shed, which we can take off underground for the greenhouse. This will more than cover the amps needed.
We are looking at the LG Model: LS307HV3 30,000 BTU cooling; 32,000 BTU heating ductless mini-split. The price is reasonable and we don't have to have any plumbing. It does require an HVAC installation, but a couple of MOS members have these units and they have some install guys who can do the work at a reasonable cost.
We are going with two 40W LED lights and 3 corrosion resistant ceiling-mount fans. We are adding 4 extra outlets and the hot-water heater. I did spring for the overhead hose trolley.
For the foundation, we are going with a concrete slab sloping to a large drain at one end. We are building up a 3' pony wall so the peak will be 12'4".
