Q:  What plants can be grown in this greenhouse?

A:  We have grown tomatoes, green beans, carrots, lettuce, peppers and succulents. The optimal plants for your greenhouse will vary by region.

Q:  Is it suitable for a residential backyard?

A: A residential backyard can be an ideal location for this greenhouse if it receives a minimum of five hours of direct sun on a clear winter day.

Q: What advantages does this greenhouse have over other greenhouses?

A1:  Sustainable Heat Source – Common heated greenhouses use fossil fuels to provide heat during the cold months.  Rather than fossil fuels, this design uses two infinite, free, naturally occurring sources of heat: the sun and the earth.

A2:  Weather Resistance –  The clear panels, through which the sun passes, are clear, multi-layer polycarbonate, warranted by suppliers for greater than ten years. They are impermeable to wind, hail, and snow accumulation.  With common hoop greenhouses, the thin polyethylene film covering can be easily punctured or ripped, and must be replaced every year or two. Common hoop greenhouses also require fossil fuel heaters.

A3: Insulation –  Rigid foam insulation is used in the structural walls to minimize thermal losses.  Then in-ground rigid foam insulation retains interior heat.  Common hoop greenhouses do not have either of these.

Q: Will I need to hire a contractor, or can I do the work myself?

A: A person with experience in wood frame construction should be able to build this greenhouse, with some manual labor help. Short of that experience, we recommend you find a construction professional. It is important to build the first tier ground beams level within ¼”, and true and square, to ensure a proper fit for the glazing panels.

Q: How much do the parts and materials cost?

A: Lumber, hardware, roofing, polycarbonate sheets, aluminum trim, rigid foam insulation, thermostatically controlled fan and motorized louver vents, paint, exterior door, and water barrels cost approximately $6500 in 2018 dollars. You will also want to consider the cost of site leveling (if needed), bringing in electrical service, and obtaining a building permit (if required in your area).

Q: Do I need an in-ground drainage system?

A: We have operated very effectively for several years without one. Your situation will depend on the area of watered surfaces and whether or not you capture any of the water that drains from the plants.

Q: What sort of maintenance does it require?

A: This permanent structure only requires minimal maintenance such as re-caulking the seams and sporadically touching up the paint.

Q:  Can it be operated off the grid?

A:  The current design requires a low level of electrical current to operate a thermostatically controlled exhaust fan and vent louver motor.  If the design were modified so that these operations were performed by a solar powered system, then the greenhouse could operate off the grid.  

Q: How can I learn more about gardening in unheated greenhouses throughout the year?

A: The best source we’ve found is Eliot Coleman’s book The Winter Harvest Handbook: Four Season Vegetable Production for the 21st Century. He operates on a larger scale with a modified portable hoop greenhouse, but his methods and observations apply to unheated greenhouses in general.

While living in the Northwest we became used to sustainability and alternative energy as a way of life. So one of the first buildings I noticed on the Emerson Waldorf School campus was the greenhouse. On close examination I was extremely impressed by the simple yet highly efficient design of the greenhouse.I was quickly informed that the greenhouse is used as a teaching environment for botany and sustainability classes, and as a test lab for growing a variety of plants over the winter. It was constructed by two faculty members and an EWS parent from a set of plans from Solstice Solar. Having some avocational carpentry experience, when I looked at the plans and instructions I was very impressed by the detail, thoroughness and thoughtfulness. The overall greenhouse design is optimal for gathering light and heat, is insulated for maintaining warmth in the coldest months, and effectively sheds snow and ice. I’ve since become friends with Rob Rich the designer of the campus greenhouse. I know him for using his talents as a former aerospace engineer to further his dedication to sustainability and in particular designing optimal solar energy systems.

–Mark E-W