Shippable Passive Solar Greenhouse Project

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Shippable Passive Solar Greenhouse Project

Several years ago I began a search for detailed drawings and building plans for a Passive Solar Greenhouse. A Passive Solar Greenhouse is one that does not use costly, artificial heat sources such as electricity or propane to heat the greenhouse when it is cold, but instead utilizes the sun as a source of heat to heat water, masonry, stone or other heat holding material.

The main objective with passive solar greenhouses is to grow plants for extended periods, past their usual growing season, and year round preferably. An aquaponics system may be included in the project.

My search for a contractor that would construct a building on site to my design without architectural drawings or materials list came up empty. I decided to take my design to a builder of out buildings and sheds with the idea of building a shippable Passive Solar Greenhouse that could fill the void for those seeking the same thing I was: Year round (including in the dead of winter) fresh salads and veggies from a source I trusted, without high cost of winter greenhouse heating.

After some back and forth with the manufacturer regarding my design, we were able to produce a finished product. The PS greenhouse is 12′ x 20′ and designed with an open bottom, as in floor-less, to take advantage of ambient temperature of the earth. If you have been in a cavern you know what this means. For example, the temperature inside Luray caverns near my home is a constant 54F degrees year round.

Passive Solar Greenhouses differ from traditional greenhouses in that only the South facing side has glazing that allows sunshine in, the remaining sides being insulated. In addition, in my design, the North facing wall is covered with black plastic barrels (50 and 58 gallons each) that act as heat batteries.

The North facing wall is also insulated with R13 insulation and further insulated by the use of Reflectix reflective insulation. The Reflectix product not only adds to the insulation value, but bounces the sunlight around inside the Greenhouse to better benefit the plants.

Physics lesson: A drop of one degree per pound of water releases 1 BTU (British Thermal Unit, the traditional measurement of heat). My barrels should represent at least 500 gallons of water. This is a weight of about 4150 pounds (water is 8.3 pounds per gallon) If the water temperature drops 10 degrees then the barrels will release 41500BTU’s of heat. A 20 degree drop would mean 83000BTU’s of heat. For perspective, typical home furnace ratings start at 80000 BTU’s.

Glazing is at a 40 degree angle to take advantage of the solar aspect in winter.

The day I took this photo, the outside temp was approximately 30F degrees.

The addition of an insulating curtain to cover the glazing and retain heat in winter (as well as shade from heat in summer) is an option in this design. There are ventilation fans to cool things off when the heat gets too high, year round.

Current status of our project

 

Photo from the net showing what our finished design will resemble in regards to the grow beds

Included here are some early photos of the project. I will have additional updates from the project along the way. If you are interested in more information on obtaining one of our shippable Passive Solar Greenhouses let me know!

By | 2017-05-16T18:24:29+00:00 March 20th, 2017|Uncategorized|2 Comments

About the Author:

Michael obtained his Permaculture Design Certification via Geoff Lawton, PRI, in 2013 , and had been a student of Permaculture Design independently for many years prior to obtaining the PDC. He is formerly trained in teaching Permaculture, and is a Graduate student in Agroforestry at the University of Missouri. His interest in Permaculture came through an interest in sustainable food production and a desire for nutrient rich foods. He is particularly interested in the value of food forests, perennial food production, and medicinal plants and herbs. Michael's experience as a licensed Financial Advisor and prior career in hospital administration and Human Resources have given him unique perspectives on the economics of Permaculture Design and the management of inputs. Michael is presently creating a demonstration site on acreage in the northern Shenandoah Valley of Virginia (temperate climate). He is also looking to work in Aid work situations worldwide to further his experience in varied climates. His ultimate goal is to teach the PDC and Agroforestry domestically as well as abroad in developing countries where quality nutrition is not readily available. He is available as a permaculture design consultant and lecturer. His Bio here: http://permacultureglobal.org/users/8798-michael-cooley

2 Comments

  1. gastone March 24, 2017 at 12:52 pm

    Mike, did you consider excavating below the frost line for a little more geothermal stability, or was it too cost prohibitive?

    • Michael Cooley March 24, 2017 at 1:07 pm

      We did indeed. The original plans were for it to be 4 feet in the ground. Costs and difficulties with excavation made the build more conventional UNfortunately

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