The underground greenhouse method allows for natural insulation, while optimizing solar absorbance. These partially subterranean greenhouses appear to be the best for growing winter horticultural crops, and have been adopted in numerous countries, such as Japan, Russia, Korea, and now even the United States. These underground greenhouses can be something built very small for an individual or family, or it can be much larger to accommodate for more commercial needs. But it has proven to be more beneficial for growers than conventional methods which are at the mercy of varying weather conditions. Cheaper than aquaponics, but more effort than urban homesteading, an underground greenhouse is almost universally viable, more than affordable, and ecologically smart.
|Underground greenhouse diagram via #OccupyTesla|
Oehlers method utilizes a coldsink to help keep warmer while Greigers plan utilizes insulation between bags and earth. All 3 plans utilize a form of thermal mass to retain warmth.
Here is a video of a tour of the Walipini underground greenhouse:
Directory pertaining to the Wallipini underground greenhouse method.
Mike Oehler book to purchase
"Earth Sheltered Solar Greenhouse" - pit construction