The Underground Walipini Greenhouse, developed by the Benson Institute http://bensoninstitute.org/ , is an interesting green house for cold or adverse environments. It utilizes nature’s resources to provide a warm, stable, well-lit for year-round vegetable production. The word ‘Walipini’ comes from the Aymara Indian language and means ‘place of warmth’.
One of the main principles involves embedding the greenhouse in the earth to take advantage of the earth constant temperature to store the solar energy collected during the day. The solar gain comes through a light permeable material such as plastic, Visqueen polycarbinate. The angle of the panels is designed to be 90-degrees to the Winter Soltace sun ( Dec. 21/June 21, depending on hemisphere).
A thick wall of rammed earth at the back of the building and a much lower wall at the front provide the need angle sheet roof. This roof seals the hole, provides an insulating airspace between the two layers of plastic ( a sheet on the top and another on the bottom of the roof/poles) and allows the sun rays to penetrate creating a warm, stable environment for plant growth. The upper portion of the walls are insulated down past the frost line.
Water barrels can also be used to store the thermal heat and carry it through the night or cloudy days (which are not as cold). Water is a much better thermal mass storage mechanism than soil. The chimney system provides the highest volume air flow and the best control of ventilation.
Walipini style greenhouse is a hydronic growing system arranged in an elevated tiered fashion (tent-shaped rows). A cheap, effective year-round greenhouse method!