What an intriguing idea. Do you think he’ll be able to rig up some sort of solar panel power, or are you going to rely on electric grow lights?
I am hoping that this year is the year we get our greenhouse/sunroom set up on the back patio. Right now I grow some plants in the winter inside the house in front of that patio door, but it crowds my computer area, and I can’t grow as much fresh stuff as I would like.
With an underground greenhouse, you still get the light of the sun from the South, but because most of the wall area is underground the plants never freeze or get too hot. Like a cave, it can be kept at a constant 70-80 degrees. It would have hydraulic panels that open on top when the temp gets too hot. It would have a berm on the back (North) side of it, which also helps keep the temp constant, and would have tubes that run under the ground, with one end opening outside on the North end and the other opening in the floor or bottom of a wall on the inside. When the panel opens on the roof, it will cause a draw from the pipe and bring in the ground-cooled air.
There are all kinds on the internet. They are called sink greenhouses, walipinis, etc. A century-old house down the highway from me has one in it’s front yard.
I just really like the idea of growing things year-round and hopefully I will be retiring in a few years & can enjoy it when gardening gets to be too much work.