Geothermal Greenhouse – Your Questions Answered

Building and managing your own geothermal greenhouse might just be the ultimate way to go green and finally take control of your health destiny.

It allows you to grow your own food in a self-contained ecosystem, repurpose waste to use as compost, and the only heat you need to keep it warm throughout the winter comes straight from the earth. It doesn’t require much at all, and it’s pretty easy to maintain once you’ve set it up.

Then possibly the biggest benefit of all is that you’ll know every single ingredient that you and your family eat. In a greenhouse you can filter the air if you’d like so that you’re not just organic, but super organic with none of today’s modern pollutants affecting your food.

You’ll know everything that was prayed on them, the water quality, the air quality and of course the soil quality as well. For the first time, you’ll truly know what you’re eating.

In the following sections, we’ll answer all of your most pressing questions. Then, along with helping you decide whether or not it’s a good fit for you, we’ll run through some of the most common issues and concerns that other newbies have when setting up their first greenhouse.

Buckle up, and let’s get this show on the road because you have to plant the seeds in your mind before you can plant them in the ground.

What Is A Geothermal Greenhouse?

A geothermal greenhouse is a lot like a mini, climate-controlled, room for all your plants. However, instead of using fancy equipment or anything like that, you simply use the thermal energy from beneath the earth’s surface to heat it up and create a suitable environment for plant life.

I know we just made that seem like something no more complex than baking apple pie, but there’s a bit more to it than slapping a tent on top of some dirt. Accessing and utilizing the geothermal energy requires a semi-complex piping setup. However, the technology used is rather primitive, and you shouldn’t have any problems figuring it out. We’ll touch on that more later on.

How Does Geothermal Heating & Geothermal Cooling Work?

In order for your greenhouse to work as planned, you’re going to have to tap into the geothermal energy below the earth’s surface. To do that, some basic piping systems will be needed to direct that geothermal heat into your greenhouse instead of letting it dissipate to the four winds.

There are two main ways of doing this: Horizontal pipe layouts and vertical pipe layouts. We’ll start with horizontal since it’s the most popular method.

Geothermal Horizontal Heat Pipe Layout

This is the most common type of piping system used due to its efficiency and low digging requirement. Basically, plastic pipes are laid in a large circle about 6 or 10-feet underground. That’s where the earth begins to hold its own thermal energy without being affected by the air temperature from above. The temperature in this zone never fluctuates out of the 45-75-degree range; Making it perfect for plant life.

However, you have to transfer that heat into your greenhouse to actually use it. So, a heat exchanger and a liquid solution are necessary. The solution, which is usually an anti-freeze chemical, is pumped throughout the ground loop and into the heat exchanger which sits inside your greenhouse.

As the solution is pumped underground, it collects the geothermal heat and brings it to the surface. The heat exchanger absorbs that heat, and with the help of low-energy fans, it blows that heat throughout your greenhouse. Then, the liquid is pumped back underground to start the cycle over again.

There are some more primitive methods that allow you to direct the heat up to the surface by simply attaching “vent” tubes to the ground loop, but they’re not as controllable, and this more modern method requires practically no electricity when compared to traditional HVAC systems. So, it’s still an extremely green option without sacrificing practicality, as such it’s the system we recommend.

That being said, if you’re on a budget the HVAC system does work well and here’s how you’d do that.

Dig out 10 feet deep, by 8 feet wide by 20 feet long (or 70% the length of your greenhouse) hole. Lay your 6-to-8-inch HVAC flex tubing over the area using stakes to keep them 6 inches apart.

Set up your 2 blowers (fans/air movers) so that it blows equally through half of the tubes on one end (in one direction) and the other half on the other end (in the other direction) with the unconnected tube ends sticking up at least 2 feet with round grates covering them to limit debris from falling into them.

You’re simply blowing half of the air in one direction and the other half in the other. You set them up on a thermostat so that if it goes below your desired temperature the units kick on.

The only issue with a horizontal setup is that it requires quite a bit of space. One can fit in a large suburban backyard or a rural environment very easily but putting one outside your home in the city is may be nearly impossible. That leads us to our second method.

Geothermal Vertical Heat Pipe Layout

Vertical pipe systems are harder to install due to the depths that need to be dug, but they take up a lot less room than horizontal ground loops. Rather than being laid out in a wide circle, they can be tightly tucked into a small space and still provide adequate results.

First, rather than digging to about 8 to 10 or so feet, you’ll have to dig up to 400-feet below the surface for each pipe you install. Unless you know what you’re doing, you might need a professional’s help just to drill the holes. The holes should be placed where your greenhouse is going to ultimately end up.

Then, long PVC pipes are inserted into the holes, and they exit the ground slightly, exposing the tips to your greenhouse area.

Like the horizontal method, it is most efficient to use an anti-freeze solution and a heat exchanger system to utilize the geothermal heat. It works exactly like it does with the horizontal ground loop, but you might need more pressure to pump the liquid since you’re pumping vertically for long distances.

This method isn’t used very often, so we definitely recommend a horizontal ground loop if you have the space for it. Digging 400-foot holes really isn’t all that fun. However, it’s your only solution if the topsoil is overtly thin, or if you don’t have enough room for the alternative.  

Geothermal Cooling

Since this type of greenhouse works by filling an insulated room with ground heat, it only makes sense that it’s usually cooled by simply letting that heat escape. Closable ventilation holes are often put into the greenhouse to allow you to cool it down a bit by simply opening them up for a while.

You can speed this up and complicate the process by adding fan-based ventilation systems that push the hot air out of vents whenever you want. Like we said, this complicates the process, and it’s not entirely necessary.

Finally, you have a third option. The same heat exchanger you use to drag heat to the surface can be used to push it back underground in some cases. This is a bit more high-tech, but if you have the means to do it, you might as well try it out.

Basically, the heat exchanger uses the heat in the greenhouse to heat up its liquid solution, and then it pumps it underground to be dissipated back into the earth. It’s as simple as flipping the equivalent of a reverse switch, but it costs a little more, and it continues to use electricity. That sort of defeats the purpose of minimizing your electricity usage with your greenhouse.

Can I Build A Geothermal Greenhouse In My Backyard?

Technically speaking, you can build a geothermal greenhouse wherever you have room to do so. That includes your backyard.

Whether or not someone is going to complain about your greenhouse is dependent on several factors. First, if you live in a fancy neighborhood, your HOA will probably have to approve of it before you start building.

Beyond that, you need to check your local laws before building anything on your property. You will most likely need a building permit, and you’ll have to follow any regulations your local lawmakers have put in place. Before you invest a single penny into this project, make sure you contact local regulatory authorities to make sure you’re on the safe side. We simply can’t cover every municipality.

There are also a few safety hazards you need to worry about. You will be digging, and you’ll be digging relatively deeply at that. You do not want to gleefully jam your shovel into unmarked ground just to be blasted to bits because you hit a gas line. Telephone lines and other utility lines are hidden beneath the surface, too.

To deal with this, call your local ground marking service before you dig. Some areas provide this service for free, and they typically come out to mark your land within a day or two. If fees apply in your area, they’re a lot cheaper than a funeral or compensating an electrical company for destroying their lines.

What Does A Geothermal Greenhouse Cost To Build?

The cost of your finished greenhouse will fluctuate quite a bit depending on what you can do on your own, the materials you use, and any permits or fees your municipality requires for building. Also, you should keep in mind that it’s a somewhat permanent addition to your property, and that may raise your property taxes. This is offset by it increasing the value of your property in some places.

In general, for a 1000-ft greenhouse, you’ll be looking at a $2000-$7000 price tag. That price increases as the size of your unit does, but you really don’t need a greenhouse that can handle an entire farm in your backyard. 1000-ft is more than enough for most residential uses.

You can also lower your overall greenhouse costs in the long run by utilizing its own natural abilities a bit more.

You’re doing this in the name of going green, right? So, why would you want to buy expensive fertilizer from a local gardening store to feed your plants? You have a complete ecosystem of your own, and it produces its own plant food!

As your crops grow and produce waste, you can put that waste into a simple compost bin, and you can reuse that to feed your plants. It only takes a couple weeks for your plants’ waste to be turned into compost, and it’s completely cost-free and low on labor demands.

You can find complex compost bin plans online, but you can also use a simple trashcan or large wooden box to create your compost, and it will fit right inside your greenhouse.

What Depth Do Greenhouse Pipes Need To Be?

This depends on what ground loop design you use. A horizontal ground loop doesn’t need to be dug very deeply. The geothermal energy you need to make it work effectively is only about 8 to ten feet below the surface, give or take a foot. It’s not an exact science, and as long as you get within that range, you should be perfectly fine.

A vertical setup might have to be dug up to 600-feet, but it’s typically only necessary to go up to 400-feet. That’s obviously a lot deeper than a horizontal rig, and for that reason, you’ll probably have to hire a professional with the equipment necessary to drill those holes.

What Type Of Soil Is Best For Geothermal Greenhouses?

The best soil for geothermal purposes is comprised of clay or wet sand particles. If you have dry, sandy soil on your property, it won’t transfer heat very well, and making an efficient greenhouse with it will be a painstaking task. Luckily, land like that is only found in a relatively small portion of North America. So, you most likely won’t have to worry about it.

If you do live in one of those areas just change the soil composition before covering the pipes or tubes.

Do Geothermal Greenhouses Work In Cold Weather?

This is actually what they’re intended for. They allow you to create and manipulate a miniature ecosystem in your backyard and effectively skip cold weather patterns to maximize your harvest. In some areas that are always cold, a geothermal greenhouse is the only way to grow reliable food sources at a low cost.

What Crops Can I Grow In A Geothermal Greenhouse?

Since you control the climate in your greenhouse, a little tinkering and attention to detail will allow you to grow just about anything. There are stories of people in temperate climates successfully growing fruits that only grow in tropical environments right in their backyards. You just have to pay attention to what your preferred crop needs, and then you have to change your greenhouse’s climate to promote the growth of that crop.

It might take a bit more work to grow plants that are extremely outside of your area’s climate parameters, but it can be done with a bit of experience and patience.

Get Started Today!

If you’re looking to go the green route with your lifestyle, or even if you’re looking to be a little more independent of the supply chain in an uncertain society, a geothermal greenhouse can provide you with a green, sustainable, food source that doesn’t require much upkeep after your initial investment.

More importantly, it uses such a little amount of electricity that you’ll be able to manage it almost completely independent of fossil fuels.

Don’t wait to jump on the opportunity for food independence and a more eco-friendly lifestyle; Start planning your own geothermal greenhouse, today!