Chinese Design for Passive Solar Greenhouse

Courtesy of James K., Virtually Green, San Francisco, CA

In northern China, solar passive commercial greenhouses cover over 1.8 million acres. These greenhouses typically use no supplemental lighting, and little or no heating, to produce vegetables from Fall through Spring. It’s a highly evolved and very commercially successful design, and virtually unknown in North America.

One of the central design precepts of the greenhouse is a high volume to surface area ratio, which ensures a large interior thermal mass in the soil, air and back walls relative to the surface area of the glazing.  At the end of a day of Winter sunlight you close the thermal blankets and the internal large volume of thermal mass efficiently retains the sun’s heat.

The Chinese designs are typically from 26′ to 46′ in width.  The 26′ width though is considered less than optimal, with most of the greenhouses closer to the 46′ width:  these wider greenhouses have much more favorable volume to surface area ratios than the narrower ones and they maintain higher and more uniform soil and air interior temperatures.

In a Calgary winter a 10′ x 10′ design won’t give you enough volume to surface area to maintain an adequately warm and stable interior soil and air temperature for optimal, or even adequate, plant growth.  And a 50′ x 14′ design is suboptimal because it’s so narrow:  You should consider widening it to at least 30′, and even wider if you can.

I work with cities and counties in the USA regarding zoning and building codes routinely.  I definitely don’t recommend building a greenhouse in a city where one grumpy neighbor can bring the codes officials down on your head and perhaps hit you with a hefty fine or shut you down.  Plus, of course I think the solar passive design won’t work well at 10′ x 10′ anyway.

So I recommend building your Chinese solar passive greenhouse outside of town and widening it to at least 30′, or wider if you can.