Underground Greenhouse

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It is a well know fact that mother earth provides the best Geo thermal mass heat source there is. Modern greenhouses continue to improve with innovation. By using the earth’s resources, there is no better way to grow than by tapping into the earth’s geothermal energy source with an underground greenhouse.

Many greenhouses today are built from a variety of materials, however, in order to have a successful year long garden venture, requires planning and proper use of materials and resources. It is no secret that a successful underground greenhouse requires advantageous location and good ground positioning.


How to capture and retain the heat produced from a well structured greenhouse is more valuable when planning to grow all year long in cold climate regions. The ground in which we produce vegetables and greens needs to be constant, digging deep into the ground provides constant temperature. If the cultivated ground within the greenhouse is maintained at or around 55 degrees or better, plants will not wither or die.

With that in mind why do successful underground greenhouses continually thrive by going deep into the ground?

Topical greenhouses do warm the ambient airspace within a greenhouse, however if the earth below and around the greenhouse perimeter freezes, the in ground plants inside the greenhouse will most likely remain dormant with little growth until the ground warms up.

Freezing ground spreads much like water and ice.

The colder it gets, the harder the dirt. Keeping the earth warm and collecting stored heat under the greenhouse is as equally important as circulating warm air throughout the greenhouse structure.

Digging an area 4ft – 8ft underground and capturing and storing daytime solar heat are the most essential principles in building a successful all year long underground gardening greenhouse.


Here’s an excerpt from Survival plus

Two other simple things are crucial to the success of our greenhouses. The earth below them is insulated to a little below the frost line with plastic foam. At night, an insulating curtain is drawn over the clear south wall to reduce high heat losses”.

Greenhouse growing continues to be a viable option across the country. For those that want more and live in colder climates, the best way to grow all season long is to construct a pit or underground greenhouse.


Requires thought with determination and guidance. Accomplishing a garden shed or an underground greenhouse structure to last and yield crop for many years is not out of reach. Building an underground, pit or in-ground greenhouse does not require a massive pit 8 feet deep, although that does help.

It is all about retaining heat with the aid of properly placed material for thermal mass retention. Most frost lines are generally 3 to 4 ft deep which will require a reinforced concrete stem wall.


Growing beds should also be about 12-18-24″ deep. A walk-in side door must also be configured to allow access into the greenhouse from the outside.

Each side should have ventilating windows. Make your pit about 6 feet deep to allow for rock medium as a base for drainage and 4″ corrugated solid tubes.

Serpentine the tubes evenly throughout the floor of the greenhouse space every 18″ apart. Add about 20″ of lush top soil and organic matter on top of the medium and tubes.

The tubes deliver warm airflow under the dirt, which blows in from the top of the greenhouse, powered with inline solar operated fans.

The warm air from the top will circulate throughout the floor of the greenhouse keeping a comfortable ground temp for warm root loving plants and greens.

For greater thermal mass heat retention, insulating the concrete walls on both sides is also recommended.

To store collected heat, use water barrels or square cans filled with water and glycol painted black as this will store collected heat which will disperse throughout the evening.


Sit low to the ground, it is like an underground room with a transparent roof.

The access door will go down a ramp to the growing field, the temperature will feel somewhat humid and warm.

The plant growth in this environment is spectacular, yielding a healthy harvest all throughout the year.

The in ground greenhouse without a doubt, is the best for utilizing the energy of the sun and soil. The best for healthy plant and herbal growth.

Whatever your growing needs, learn and invest to use God’s gift of the sun and soil wisely.


Your solar underground passive greenhouse will provide abundant harvests year after year. to sum it up … an encapsulated view of what an underground greenhouse is all about…
Please feel free to reach out and read the additional resources that are on this page. Contemplating one, then by all means contact Ralph for designs and estimates and materials. In need of local polycarbonate panels… good prices, lots in stock… fast availability for Colorado locals U pick up save on freight and crating

Earth In-ground Greenhouse Resources:

The Walipini

The Winter Greenhouse

Learn how to care for and maintain a Greenhouse

Solar Greenhouse that’s right for you


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