Walipini Construction (The Underground Greenhouse)
24 pages of useful underground greenhouse (Walipini) information along with design and construction ideas and plans.
Over 20 images
- How the Walipini works
- Earth’s Natural Heat — Why dig in?
- More Free Energy — The Sun
- Heat Storage — Mass/Flywheel
- Cutting Heat Loss – Insulation
- Location of the Walipini
- The Danger of Water Penetration
- Digging into the Hillside
- Maximizing the Sun’s Energy
- Alignment to the Winter Sun
- Angle of the Roof to the Sun
- Walipini Design
- Size and Cost Considerations
- Venting Systems
- Method 1
- Method 2
- Method 3
- Method 4
- Interior Drainage System
- Exterior Drainage System
- Water Collection Drainage/Heating System
- Building the Walipini
- Tool List
- Materials List
- Laying Out the Building
- The Excavation
- The Walls
- Roof and Glazing
- Berms & Exterior Drainage
- Venting Systems
- Completion and Charging
How the Walipini Works
The Walipini (underground greenhouse), in simplest terms, is a rectangular hole in the ground 6 to 8 feet deep covered by plastic sheeting.
The longest area of the rectangle faces the winter sun – To the north in the Southern Hemisphere and to the south in the Northern Hemisphere.
A thick wall of rammed earth at the back of the building and a much lower wall at the front provide the needed angle for the plastic 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 allows the suns rays to penetrate creating a warm, stable environment for plant growth.
The Earth’s Natural Heat — Why dig in?
The earth’s center is a molten core of magma which heats the entire sphere. At approximately 4 feet from the surface this heating process becomes apparent as the temperature on most of the planet at 4 feet deep stays between 50 and 60º F.
When the temperature above ground is cold, say 10º F with a cold wind, the soil temperature at 4 feet deep in the earth will be at least fifty degrees in most places.
By digging the Walipini into the ground, the tremendous flywheel of stable temperature called the thermal constant is tapped.
Thus, the additional heat needed from the sun’s rays as they pass through the plastic and provide interior heat is much less in the Walipini than in the above ground greenhouse.
Example: An underground temperature of 50º requires heating the Walipini’s interior only 30º to reach an ambient temperature of 80º. An above ground temperature of 10º requires heating a greenhouse 70º for an ambient temperature of 80º.