Heat loss can be prevented by double glazing for the winter with bubble plastic but it can present problems with condensation.

Bit concerned about the plastic bags though. They will breakdown quickly if they are not ultra violet resistant. The plastic will be OK but how will you block the corrugations?

No ideas about the water circulation though.

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Gardening requires a lot of water - most of it in the form of perspiration. Lou Erickson, critic and poet