Underground Greenhouse (pdf)

[BDG]

Its not such a good idea in the UK, we are too far north so the sun is low - for it to work as it should, the 'roof' would have to be at between 65 and 70 degrees from the ground - much closer to vertical than horizontal. It is not that we have particularly cold winters in the UK, the biggest problem we have here is lack of sunlight. It is quite simple to keep a greenhouse above freezing and it does not take a lot of fuel to keep winter salads and greens in their happy climate, it is just that they do not get enough sun to do a lot of growing.