A Chinese greenhouse with metal support beams and a heat-banking back wall coated with soil-cement or cement stucco. A walkway against the back wall is a handy addition for harvesting and tending to plants. Photo by Dr. Sanjun Gu and courtesy Dan Chiras
Many market gardeners and home growers struggle with how to grow produce throughout the dead of winter without running their bank accounts into the red paying exorbitant greenhouse heating costs. This is because, for conventional greenhouses, benefits are felt during daylight hours when heat is trapped inside but as soon as the sun sets, heaters (typically fueled by gas or electricity) are fired up to maintain temperatures plants can tolerate. By one account, a greenhouse in Iowa growing tropical fruit year-round is faced with a $20,000-per-month utility bill!
For those gardeners who wish to grow year-round — and we are talking truly year-round gardening of hot-footed favorites like tomatoes and peppers, not merely season extension techniques or growing only the most cold-tolerant of plants— longtime MOTHER EARTH NEWS Contributing Editor and home-energy expert Dan Chiras has a solution for you: the Chinese greenhouse.
Chiras’ latest book, High-Performance, Off-Grid Chinese Greenhouses breaks down “year-round aquaponics and soil-based gardening powered by solar energy” with concise and comprehensive instruction supported by dozens of diagrams. Before you’ve finished the book’s introduction, Chiras will have you convinced that these typically submerged, passive-solar inspired structures whip the competition without using an ounce of fossil fuels for heating. The book is available from The Evergreen Institute.
What is a Chinese Greenhouse?
Information on Chinese greenhouses is decidedly scant, and so you won’t find another book like this one. Searching the term online, Appropedia.org offers a nice, but short, writeup with video, and Low-Tech Magazine ran a feature in 2015. You’ll otherwise find ad-sponsored pages from companies hawking aboveground kits.
The technology is thought to have emerged during the mid-1980s (perhaps surprisingly recent) as a means to support a fast-growing population hungry for vegetables and living in snowy climes at 30 to 41 degrees north latitude — about the same latitudes as much of the United States. In 2000, there were about 650,000 acres of Chinese greenhouses in operation throughout the country.
At its most basic, Chinese greenhouse design involves:
• An axis oriented east-west to capture fall, winter, and fall sun low in the sky
• Comparatively small interior space to make heating and cooling easier
• Significantly less glazing to reduce surface area that leads to nighttime heat loss
• An insulating blanket of some kind that is rolled up during the day and rolled down atop the glazing at night in order to trap heat inside
• Tons of thermal mass to store heat during the day and re-radiate it at night
Typically earth-banked into a hillside or girded by mounded earth, you can already see that Chinese greenhouses bring many principles of passive-solar design into the greenhouse in order to grow using 100-percent solar radiation. No heat need be provided from propane, wood, natural gas, or other sources, which really sets this system apart from any North American year-round greenhouse.
Chiras writes that first-generation Chinese greenhouses were simple structures made from local materials, including bamboo poles and steel wire. A thatched-grass blanket was rolled up during the day to allow sunlight to pour in through the glazing and is then systematically unfurled each night to provide insulation that traps in the heat radiating out from the structures’ thermal mass.
Design for a Chinese greenhouse constructed at The Evergreen Institute in Missouri. Illustration by Forrest Chiras
Greenhouse Thermal Mass, Glazing, and Drainage
Chiras admits early on that he is not an expert in Chinese greenhouses — in fact, the book was published before his first attempt at building one had completed a full year of growing.
But a reader should never once take this disclosure to mean she is thumbing through the speculative work of an amateur. Chiras is a world-class home-energy expert and understanding passive solar design for homes is one of Chiras’ specialties. This is what makes him supremely capable of conveying the design elements to a newbie (like me).
In addition to expertise in heat-banking (you’ll learn how to choose between your thermal mass options for flooring and back walls: concrete, brick, adobe, or soil-cement), pros and cons of various types of glazing (ETFE sheet plastic, Solarwrap, reinforced polyethelyne, or polycarbonate), and insulation options (Tempa Interior Climate Screen or radiant barrier), Chiras offers his tried-and-true opinions for best places to site your Chinese greenhouse and how to troubleshoot many drainage problems.
Humor and Intrigue
If you are fan of Chiras’ other books (many of which are available in the MOTHER EARTH NEWS Store), you’ll appreciate that Chinese Greenhouses offers plenty of moments of Chiras’ brand of humor targeted to the wiser-living audience: “I now understand why ornithologists refer to ducks and geese as “waterfowl,” although they clearly got the spelling all wrong. It should be waterfoul.”
I especially appreciated his conversion technique of converting greenhouse costs into graspable metrics, i.e. heads of lettuce: “If lettuce grown in the greenhouse sells for $2.00 a head wholesale, you’d need to sell 10,000 heads each — just to break even on the plastic.”
You’ll also appreciate the book’s accumulation of scientific facts that support the author’s advocacy for Chinese greenhouse design but are broadly applicable to all gardening situations: “As it turns out, photosynthesis begins to slow down in most plants when the temperature reaches 85 degrees Fahrenheit. It grinds to a halt at 100 degrees.”
Chinese Greenhouses is intended to be one of Chiras’ more “living” volumes, so plan to see updated editions in the next few years as his design experiments come to fruition. Were I to offer an idea for a unique bonus, I’d suggest Chiras supply purchasers of the book with a coupon that entitles them to one free e-book download as the later editions are published.
If you’re considering building a greenhouse — any type of greenhouse, really — buy this book and read it cover to cover to firmly plant your feet in the basics of glazing, framing, and heating. Find it at Chiras’ website.
I’ll leave you with a few of his lyrical words that remind us why on earth we undertake the head-scratching, and sometimes hair-pulling, endeavor of greenhouse growing in the first place: “We rarely left before 10pm. And only then we had to tear ourselves away from the warmth, pleasant smells, and luxuriant green plants growing like weeds in our greenhouse. It was a world in and of itself — comforting and healing.”
High-Performance, Off-Grid Chinese Greenhouses (Dan Chiras, 2016)Read Dan Chiras’ blog posts and articles for MOTHER EARTH NEWS here.
Kale Roberts is Blogging Coordinator and a former editor of MOTHER EARTH NEWS. His interests include renewable energy, climate action planning by local governments, and sustainable rural development. You can find him on Google+.