This post originally appeared on our sister site A Prepping Homestead:
Feeding the family fresh organic produce year round is a wonderful, yet expensive, reality we have right now from our local health food store. Yet we want to able to produce this for ourselves to save money now, and in the event that for whatever reason we can no longer go purchase great fresh produce at the store.
Of course we over produce in the summer and can or freeze the reserves, but we want fresh, off the vine tomatoes, peppers, salad greens, etc. year round. The challenge is that we live in a northern climate where sub zero temps are possible a few months of the year. I started research into building a greenhouse, and primarily didn’t like the requirements to heat it. It would be too much money now, and unsustainable if SHTF.
Then my mother in law posted a link on her Facebook page to an article on Walipinis. A Walipini is a very basic underground greenhouse design that has been used throughout the world as a very inexpensive yet effective greenhouse solution. The Benson Institute created a great informational article which is no longer on their website but can be found here, but the basic concept is that just about anywhere in the world the earth maintains a constant temperature around 60 degrees 6ft under ground. If you can build your growing layer 6ft down with walls of earth on four sides, the only heat loss you have is through the polycarbonate roof letting the sun in. Although there is a lot of optimism on the net as to how well this works year round, I’m certain that heating costs will be a tiny fraction of what they would be for an above ground greenhouse. Time to draw up some Pit Greenhouse plans and design requirements.
I knew we wanted something a little more advanced than the Walipini so after reading the best book I’ve found on the topic, The Earth-Sheltered Solar Greenhouse Book by Mike Oehler , as well as Rob’s ideas over at The Permaculture Research Institute, the great pictures at Inspiration Green, and many other sites, I drew up this design:
Features that we really want:
- Obviously a 6-7ft deep pit to take advantage of the earth’s natural temperature.
- A cold sink that traps the cold air at the door below the growing surface.
- Permeable walkway on top of this cold sink so it can also be used as a root cellar.
- Additional digging forward of front wall to allow as much sun in during the parts of the winter with the lowest sun Asimuth.
- Proper roof angle to provide the most light and warmth from the sun in the lean winter months, and least in the summer so as to not overheat.
- Insulating blanket to pull over the roof on the coldest nights to trap heat.
- Possible grow/heat lamps to supplement during the worst of the winter .
- Ventilation so as not to burn the plants in the summer.
- Black 55 gallon drums filled with water used as mass to store heat as well as irrigate the plants with not shockingly cold water.
It’s a big project! One we hope to accomplish for use this winter. We will chronicle the building of it, and keep you posted on what works, what doesn’t, and then the new adventure of growing in a greenhouse.
Check out Part 2 in this series regarding getting supplies together for our Pit Greenhouse.
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