Every Growing Dome® Greenhouse comes standard with a geothermal climate control system. At Growing Spaces, we call it the Undersoil Ventilation System; previously known as the central air system, or undersoil heating & cooling system. There are many different names for these types of systems, such as Climate Battery, Earth Tubes, Subterranean Heating and Cooling System (SHCS), or Ground To Air Heat Transfer System (GAHT). All of which have slight design and installation differences. Some of these names and designs hold patents and/or trademarks. The system that comes with Growing Dome Greenhouses is very different in design. It is not as complex or powerful, and therefore, much easier install. All of these systems seek to achieve the same goal. Their purpose is to utilize the consistent temperature of the soil, tap into the thermal mass, and have the ability to store and release that thermal energy. The fan(s) used in these systems help circulate the air within the greenhouse as well — bonus!
The main difference between our undersoil ventilation and a climate battery or GHAT system is that our system uses the soil in your raised beds as the thermal mass, and the other systems use the Earth below the greenhouse. Excavating the earth before your greenhouse build can increase cost, but can be useful to add additional heat in colder climates (zone 4b or below).
True geothermal heating systems actually use the heat from the Earth’s core to heat the greenhouse. Obviously, you would need access to this heat from a hot spring or a well. Luckily, here in Pagosa Springs, CO we have the deepest Hot Spring on the planet which provides heat from the ground to the town and three 42′ Growing Domes at the Geothermal Greenhouse Project. Feel free to call us if you want advice on these or other types of geothermal systems for your greenhouse.
The Undersoil Ventilation System
In order to utilize the natural thermal capacity of the soil beneath the greenhouse, perforated 4″ pipes are placed in the perimeter raised beds then buried when filling with soil. The end of the pipes protrude 3 – 6″ above the foundation wall so the soil does not fall in. The ends near the above-ground pond intake air and the ends on the south side of the greenhouse exhaust air. Mounted in a box covering the exhaust pipes, the 12 volt, 4″ fan pulls air though. A PV solar panel mounted on the Growing Dome greenhouse powers the fan. At 70 cubic feet per minute (CFM), the fan pulls the hot or cool air near the pond through the pipes and soil. This system helps warm the soil in the winter and cool it in the summer. Additionally, the fan moves and circulates air in the greenhouse in an open loop system. With our greenhouse designs, year-round growing is a reality.
It is important to note that the Undersoil Ventilation system is installed inside your interior planting beds, and may vary based on your raised bed designs and the location of your door.