Typically, greenhouses are glazed structures. They are expensive to build and costly to heat during the winter. Greenhouses in colder climates also have shorter growing seasons.
Walipini were originally developed in cold, mountainous regions of South American over 20 years ago to combat the shortened growing season. They are located 6 to 8 feet underground and capture solar radiation during the daytime and retain their warmth.
The longest area of the Walipini’s rectangle faces the winter sun. It faces to the north in the Southern Hemisphere and to the south in the Northern Hemisphere.
A plastic sheet roof stays in place with a thick wall of packed earth placed at the back of the building. This roof seals the hole and provides an insulating space between the two layers of plastic, a sheet on the top and another on the bottom of the roof, and allows the sun’s rays to penetrate creating a warm, stable environment for plant growth.
This underground greenhouse uses the thermal mass of the earth and a considerably less energy is used to heat the structure than standard above-ground greenhouses.
As long as the walipini are waterproofed properly, drainage and ventilation are considered, and alignment to the sun is accurate, the underground greenhouse can grow plants successfully year round at less cost and more efficiency.