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Solar Heated Greenhouses

Solar Heated Greenhouses

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This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.

Larry A. Sagers Regional Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved

For more information on solar design, read my column in Friday’s Deseret News.

Since the beginning of time, light and heat have come from one source. Early people knew that the sun gave them warmth and light long before they had any idea that it was a molten glob of burning gases 93 million miles from earth. The dream has always been to capture the warmth of the sun and then release that when the sun went down.

Like all gardeners, I admit to sharing the same fascination for the sun. Harvesting light and heat allows you to grow plants out of season. When the snow was on the ground and the world was cold and dreary, the fruits and flowers could continue to grow.

Solar greenhouses are one way to harvest the energy from the sun. Taking advantage off solar energy is not always easy but it does provide a clean renewable resource that enables you to grow plants out of season without burning fossil fuels.

What follows is a success story where someone learns from you, makes many improvements and ends up doing it even better.

Petersen will be assisting me in teaching the solar greenhouse construction class in January. This is the 22nd consecutive year I have taught this class. The class covers solar design and construction and covers hot beds and cold frames that are inexpensive alternative to a greenhouse. Other Utah State University personnel are also assisting with the class. Register by calling 768- or go online at and click on the education icon.

“I first got started in greenhouse gardening when a friend let us grow a few plants in their greenhouse. We got hooked on growing a few plants for our garden out of season. I then signed up for the greenhouse growing class you teach at Thanksgiving Point. It became the Tuesday night date for my wife and me.”

“I took the class a couple of more times to grow more plants and then realized I wanted more space and more time than the class allowed. I then took the solar greenhouse construction class and then built my own.”

All greenhouses are solar in the sense that they take the suns light energy and use it to grow plants. Solar greenhouses, by definition, harvest the heat during sunny days and release it at night or on cloudy days. To function successfully the greenhouse has to maximize solar gain and have one or more mechanisms to store the heat.

His principal type of heat storage is water. He selected two liter soda pop bottles because they are durable and do not break down rapidly in the sunlight and they are easy to fit into the framing design. They are also readily available.

His design includes more than 500 two-liter bottles that hold about one ton of water. These bottles absorb the suns rays during the day and releaser the heat at night. The system is totally passive so there are no pumps or other components to deal with.

In addition to the water storage, the large gravel on the floor acts as an addition heat storage. While it does not directly absorb the suns rays, it does provide thermal mass because of the insulated foundation walls.

If you own a greenhouse or have ever thought of building one, consider attending our hobby greenhouse short course. The class will cover whether you want or need a greenhouse in your gardening situation. We will also cover constructing a greenhouse with attention to greenhouse structures and greenhouse coverings. Selection of construction materials is important to keep your greenhouse safe, practical, enjoyable and efficient.

The class is Tuesdays from 2:00-4:00 or 6:00-8:00 P.M. at the Thanksgiving Gardens Visitors Center in classroom. Classes begin on January 6 and run for four weeks. The class fee is $40.00 and includes the greenhouse design booklets and other written materials. Please register by calling 801-768-7443 or toll-free 1-888-672-6040 (ext. 7443) to register to guarantee your place in the course. You can also register online at and then click on the education icon.

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