Pit Greenhouse

have any of you guys herd of a pit greenhouse. it is supose to be partly underground making the green house keep its heat. This means you dont have to pay for heat and can be stealth in the middle of my property. I was wondering if anyone has built a pit greenhouse and has any tips. I have been doing some research and it looks the best to grow haze plants in the cold washington. the pit greenhouse should give me a exstra month to harvest.

The best way to grow in cold washington is indoors. My opinion.

no it is a kind of green house mostly in canida were it is cold to grow fruit all year round. It will keep heat becuse it is underground will have cement walls!!! this guy is a genus he build a house with 500 dollors that ran off the grid it is some crazy stuff.