Jpm995,
I have not installed the greenhouse yet. I did the concret footing (6 pillars). It is not the whole foundation though.
The reason I built the 6 concret pillar is to prevent the greenhouse collaps incase of big wind ( my area does not have big wind though).
I didn't think about foundation and insulating the ground when I started.
After I do learned about this forum and everyone seems to care about much insulating the floor and ground.
If insulating the floor and ground is important like digging 4 feets, I will have to start digging. That is a huge huge effort, and I'm not sure if it make much different if I just put a layer of concrete block on the floor.
