Saturday, October 5, 2013

How to Build a Walipini Greenhouse: Grow Food Year-Round for ~$350, UPDATED

Update: This was, after all, a prototype. Numerous problems ensued, mainly the seamed strips of plastic roofing material were ripped apart easily by wind and rain - We advise buying a reinforced 'greenhouse tarp' material for a seamless roof that you won't have to replace so often. Another issue is the strength of PVC - Wood is stronger, more environmentally friendly and is more expensive to buy, but can cut from your own property for free (not counting labor). I will post a revised tutorial on my future design when my funds allow it. In general, I would advise you dig a deeper hole than the one picture, perhaps 7-8 ft deep all around with a a higher wall on one end to position the roof without an apex (a flat surface roof, sloped for run-off).

On behalf of Urban Farm Consultants, I am very excited to unveil our prototype design of the most versatile and affordable DIY greenhouse known, inspired by the Walipini commonly used in the Andes mountains, with steep farmland and harsh winters. I built mine using very inexpensive materials - the only major cost being the day rental of back-hoe (about $200).
The Walipini utilizes nature’s resources to provide a warm, stable, well-lit environment for year-round vegetable production. Locating the growing area 6’- 8’ underground and capturing and storing daytime solar radiation are the most important principles in building a successful Walipini.
The Walipini, in simplest terms, is a rectangular hole in the ground 6 ‛ to 8’ 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) and allows the sun's rays to penetrate creating a warm, stable environment for plant growth.

If you live in an area with softer soil, you may able to forgo the back-hoe if you have some friends willing to help you shovel dirt all day! The supports are made from 3 upright two-inch PVC pipes and 6 diagonal one-inch pipes for the sides (All in all costs about $100). Other designs use a single-plane sloped roof without upright supports at all and some with wooden supports. I chose this design to suit the sloped land I was building on while keeping the path of the sun in mind to maximize light penetration. I used weatherproof epoxy glue designed for plastic use and clear packing tape to join three segments of clear 4-millimeter polyurethane sheeting (100 ft/$20 on eBay) and tree limbs to keep the tension tight on all sides. I plan on using extra plastic sheeting I have laying around and attaching a zipper to it to create a doorway. I have also housed my aquaponics system inside which helps keep humidity high as well as temperature, resulting from heated water. One could easily grow salad greens such as Kale throughout the winter as well as vegetables if you're deep enough to capture thermal heat. I will house my dwarf banana, avocado and mango trees inside as well and hope they make it through the Georgia winter!

Good luck to you and if you ever need advice, send us an email!


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