Year-Round Solar Greenhouse: How to Design and Build a Net-Zero Energy Greenhouse - Softcover

Über die Autorinnen und Autoren

Lindsey Schiller studied conventional greenhouse design and management at the University of Arizona's Controlled Environmental Agriculture Center before delving deeply into solar greenhouse design. With co-author Marc Plinke, she founded Ceres Greenhouse Solutions to research, design and build energy-efficient year-round greenhouses. Lindsey lives in Boulder, Colorado.

Marc Plinke, an inventor-innovator with a PhD in engineering, started his career as a chemical and process engineer working for Gore Technologies. Marc has spent the past decade applying his expertise in green building and engineering mindset to building better greenhouses, with the intention of enabling people to grow their own food sustainably, year-round. Marc lives in Boulder, Colorado.

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Build your own passive solar greenhouse for year-round food production in any climate

Extensively researched, written with personal experience, and full of essential facts and figures rendered simple and accessible.
― DARRELL E. FREY, author, The Bioshelter Market Garden

A practical, easy-to-read guide that enables anyone to design and build their own sustainable, year-round greenhouse. I highly recommend it for aquaponic growers, and any gardener looking to extend their season.
― SYLVIA BERNSTEIN, author, Aquaponic Gardening

FRESH, LOCAL, NUTRIENT-DENSE fruits and vegetables are hard to find in winter in cold climates. Growing warm-weather crops like tomatoes, bananas, avocados, or other perennials is nearly impossible using conventional structures. The solution for millions of backyard and small-scale commercial growers is self-heating solar greenhouses.

The Year-round Solar Greenhouse is the one-stop guide to designing and building greenhouses that harness and store energy from the sun to create naturally heated, lush growing environments even in the depths of winter. Topics include the principles of solar greenhouse design, siting, glazing material properties and selection, controlling heat loss, ventilation, and construction methods. Additionally, an in-depth section covers sustainable ways of heating the greenhouse without fossil fuels, including using thermal mass and storing heat underground with a ground-to-air heat exchanger.

Variations include attached solar greenhouses, earth-sheltered greenhouses, plus integrating hydroponics and aquaponics. More than a dozen case studies from across North America provide inspiration and demonstrate specific challenges and solutions for growing year-round in any climate. Grow your own food, anytime, anywhere using the power of the sun!

An important resource that will help farmers and greenhouse operators leverage innovation for sustainable and profitable food production. ...This book should be part of your tool kit.
― GAELAN BROWN, author, The Compost-Powered Water Heater

LINDSEY SCHILLER is a greenhouse designer and is, with co-author Marc Plinke, co-owner of Ceres Greenhouse Solutions. Lindsey has designed, toured, and helped build hundreds of energy-efficient greenhouses spanning small residential structures to acre-size commercial facilities.

MARC PLINKE is an inventor-innovator with a PhD in engineering. In recent years he has focused his engineering mindset on building innovative, energy-efficient, and smarter greenhouses, with the intention of enabling people to grow their own food sustainably and year-round.

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What Is a Solar Greenhouse?

"Don't all greenhouses use the sun?"
"You mean a greenhouse with solar panels?"

Stand in front of a sign that says "Solar Greenhouses" at a green products trade show, and you'll frequently be asked these questions. Few people are familiar with the concept of a solar greenhouse. Simply put, it's a greenhouse that uses the sun's energy not only for growth, but also for passive heating; thus, it is able to maintain suitable growing temperatures without reliance on fossil fuels.

Indeed, all greenhouses use the sun for heat and growth during the day. At night, most greenhouses quickly lose all that heat due to the poor insulating quality of their materials. On a winter morning, a standard unheated greenhouse usually is only a few degrees warmer (if at all) than the outdoor temperature. Moreover, unless it is ventilated or artificially cooled, a standard greenhouse traps so much heat during the day that it will drastically overheat.

Energy author Dan Chiras once used an excellent analogy to give a quick picture of traditional greenhouses: Imagine living in a tent.1 When it's 90°F (32°C) outside, sitting in a closed tent is the last place you want to be. When it's 32°F (0°C), sitting unprotected in a closed tent is also uncomfortable. A tent offers very limited protection and insulation. Traditional greenhouses work similarly for plants; they overheat during the day if uncontrolled, and then they let all that heat out at night. The result is wild temperature swings that stress or kill plants. To compensate, greenhouse growers often blast the greenhouse with heating and cooling systems in order to grow year-round.

The reason for these inefficiencies has to do with some basic principles of design. Traditional greenhouse design focuses on maximizing light by maximizing glazing. (Glazing is a term for any light-transmitting material, like glass or clear plastic.) Traditional greenhouses are normally "100% glazed," meaning all surfaces are made of clear or translucent materials. While they are good at letting in light, glazing materials are extremely poor at retaining heat. You've experienced this first-hand if you've ever sat next to a window on a cold night - it's a chilly spot. Now imagine an entire building made out of windows. It naturally gets very cold if not heated through the winter.

Solar greenhouse designs takes a different approach. Instead of creating a fully glazed structure, it finds a balance between glazing and insulation in order to create a more thermally stable structure (one that naturally resists overheating and overcooling). Designers use glazing strategically, placing and angling it to maximize light while reducing the glazing area as much as possible to minimize heat loss. Furthermore, solar greenhouse design emphasizes storing the excess heat of the greenhouse during the day and using it for heating at night. Instead of ventilating excess heat outside, only to have to re-heat the structure at night, solar greenhouses rely on the simple greenhouse effect for heating - using the heat from the sun that is collected and trapped in the greenhouse during the day. Instead of fossil fuels, the sun provides the energy; the greenhouse collects and stores that energy, providing its own heating when it's required.

The Many Meanings of Solar

The word "solar" is an incredibly broad term - meaning relating to the sun - but it conjures up some specific images. When most people hear "solar," they picture a building with solar photovoltaic (PV) panels. Greenhouses can include solar panels to generate renewable electricity; however, a much wiser use of the sun's energy for heating is through passive solar design: the practice of using solar energy for heating without relying on any electrical or mechanical devices. Specifically, it advocates carefully enhancing solar gain and minimizing heat loss in order to reduce or eliminate the dependence on fossil-fuel- based heating/cooling.

Though passive solar heating does not use electricity, in can be applied to buildings that do. Today in the building industry, a passive solar home generally refers to a house that utilizes passive solar design. These homes usually still have electrical appliances, like a refrigerator or washing machine. Similarly, solar greenhouses rely on passive solar heating, but they often have some electrical components. Many of these electrical systems transfer heat from the greenhouse to a storage medium, like the soil or water, allowing the greenhouse to take full advantage of the powerful greenhouse effect. The term passive solar greenhouse is often used to more explicitly describe a greenhouse that uses passive solar heating and has no electrical components at all - so it uses no electricity.

As you can see, there are some overlapping terms, so we should clarify: In this book we use the word passive on its own to describe systems that don't use electricity. Active is shorthand for systems that require electricity, like fans or pumps. For us, "solar greenhouses" are those that rely on passive solar design, and can be electrical or nonelectrical structures.

The Seven Principles of Solar Greenhouse Design

Solar greenhouses vary in almost every way - their shapes, styles, sizes, building methods, and technologies. However, there are a few unifying elements that apply to them all. To put them in a nutshell (because every book needs a nutshell), we've distilled them into these seven best practices:

1. Orient the greenhouse toward the sun. In the Northern Hemisphere, the majority of the glazing should face south to maximize exposure to light and solar energy.
2. Insulate areas that don't collect a lot of light. In the Northern Hemisphere, the north wall of the greenhouse plays a minor role in light collection. It should be insulated in order to reduce heat loss, creating a more thermally stable structure.
3. Insulate underground. Insulating around the perimeter of the greenhouse allows the soil underneath it to stay warmer, creating a "thermal bubble" underneath the structure that helps stabilize temperature swings.
4. Maximize light and heat in the winter. To grow year-round without dependence on artificial lights or heaters, it is crucial to maximize naturally occurring light and heat during the colder months. This is done by using proper glazing materials and angling the glazing for winter light collection - in general, using the glazing area strategically.
5. Reduce light and heat in the summer. Growing during the warmer months can create problems with overheating. Strategic shading, glazing placement and angles reduce unnecessary light and heat in the summer.
6. Use thermal mass (or other thermal storage techniques). Thermal mass materials are materials that store the excess heat in the greenhouse during the day and slowly radiate it at night or when needed. This evens out temperature swings, creating a more controlled environment for growing. Almost all solar greenhouses have some mechanism to store heat, broadly called thermal storage.
7. Ensure sufficient ventilation. Natural ventilation ensures a healthy plant environment and controls overheating.

The Case for Solar Greenhouses

Fig. 1.1 shows the temperatures in two unheated greenhouses over a few cold, winter days in Boulder, Colorado. The first is an uninsulated greenhouse, made out of a PVC frame and polyethylene plastic. The second is an insulated solar greenhouse designed with the principles listed above.

The standard greenhouse drops to a low of 2°F (-17°C); the solar greenhouse...