Greenhouse warmed & cooled with air vents buried 8 feet underground?

Person describes warming a greenhouse in Nebraska with vent tubes circulating air from 8 ft. buried underground. Temperatures become moderated and he's able to grow oranges and other citrus fruits! Says it is super cheap to run - looks simple once the pipes are buried.



Anyone seen this sort of thing or done anything like it? I suppose it's just like geothermal. I wonder why it's not more common

So much to learn from this video!!! Thank you for sharing this.

I love Russ's greenhouse.  They are building them in a number of locations.  

To attempt an answer for your question...  I think it's not more common for a couple reasons.

1.  People looking to build greenhouses don't often stumble across this option.
2.  I believe this design requires a fair bit of sunshine to keep working (I may be wrong here).   If it doesn't need sunshine, I wish that aspect was advertised more.  In my area, and I suspect much of New England, it's cloudy for much of November and December.
3.  It's different.  They know how to build a farmtec greenhouse and pour lots of propane into it for heat in order to just barely make a profit from the plants.  That's an off-the-shelf standard way to build a greenhouse.  Doing Russ's design requires a bit of an adventurous spirit and some unconventional construction techniques (vs a normal greenhouse).
4.  I could be wrong here but I think it probably can't be built much smaller.  While many people would be willing to build their own little greenhouse and take on some novel approaches like this, they may not have the room for it in their back yard.  I'm assuming it would be challenging to use this technology in a 8x12 greenhouse and a suburban lot.

That being said, I fully support every new commercial or large scale private greenhouse being built this way.  We need more of this.

Well, we are gonna find out !  

My brother just bought a 72 footer for Christmas and we will be putting it together, in Wyoming, next spring. I hope to take lots of pictures and start a project thread about it so stay tuned.

Mike, I don't think the sun shine is needed, though I'm sure it helps as the sun light will reduce the load on the geothermal.  I would think worst case, that if sun is limited you'll just need more underground pipes or length to supply the extra heat loss from not having as much solar gain. Does that kind of match your thinking?

Is it just me or are there three separate systems:
-An eight foot deep underground loop for heating?
-An eight foot deep stretch of cooling pipe with one end coming up in the field?
-A cooling loop that goes from the peak of the greenhouse to one foot beneath the greenhouse floor and back?

The amount of digging needed for this is a barrier  for DIY types, and most people who have money to spend on the digging will be cautious about spending it on this novel solution.

All that being said, my first chicken house has tubes beneath the foundation.
They are too few in number and only 2' deep,  and I've yet to try them out.

Greg Martin wrote:Mike, I don't think the sun shine is needed, though I'm sure it helps as the sun light will reduce the load on the geothermal.  I would think worst case, that if sun is limited you'll just need more underground pipes or length to supply the extra heat loss from not having as much solar gain. Does that kind of match your thinking?

That could certainly be.  I'm not sure how much of the winter geothermal heat comes from the innate temperature of the earth down 8' and how much is from summer (and daytime winter) heat that is sent down there.  I guess my hunch is that 90+% of it comes from the natural temperature of the earth.

Good point William, that's another reason that this system (and GAHT designs) might not be as popular.

We just got back from visiting Russ and his greenhouse. It was 80 degrees with tropical humidity. It was sunny, but snow was still on the ground outside. The pipes are not only for cooling in the summer and stabilizing heat in the winter, but also for cooling in the winter if the temps get too high. He has tweaked his design since he built the one on his house and the tweaks make for more consistent heat/cooling. We shall see come spring how well this works, as we will be installing it on our property in Wyoming. I hope it does, as it was -12 degrees F last night!

Kani,  did you buy a set of plans?
How much did he ask for them?

The plans (more of a narrative with pictures) is $49. You can go to his site - greenhouseinthesnow.com to find them. There is also a FB page for a woman who is using Russ' greenhouse commercially in Cody, NE. https://www.facebook.com/Sunny-C-Greenhouse-1067197630058985/  She has many pictures and posts of what she has been growing. Interesting site.

Mike Jay wrote:
4.  I could be wrong here but I think it probably can't be built much smaller.  

This.  I was crunching the numbers and the Russ Finch/earth tube heat exchange efficiency increases per linear foot if you are putting the tubes underneath the growing zone.

Which begs the question, why not create the ground to air exchange interface as a subterranean cavern out of IBC cages to:
   1. increase the air exchange volume
   2. decrease earthtube costs

Cave ins are a potential problem, but Mike Oehler or someone here might have a solution for that.  Any other reason this approach might not work?

James Rubino wrote:

Mike Jay wrote:
4.  I could be wrong here but I think it probably can't be built much smaller.  

This.  I was crunching the numbers and the Russ Finch/earth tube heat exchange efficiency increases per linear foot if you are putting the tubes underneath the growing zone.

Which begs the question, why not create the ground to air exchange interface as a subterranean cavern out of IBC cages to:
   1. increase the air exchange volume
   2. decrease earthtube costs

Cave ins are a potential problem, but Mike Oehler or someone here might have a solution for that.  Any other reason this approach might not work?

Could you explain the past about the tubes under the growing zone in more detail?  My understanding is that the tubes can be buried anywhere you like as long as they are 8 to 10 feet deep.    There is no need to put them under the growing zone.  I'm not even sure how that would help.  The idea is to use the earth temp for heating and cooling,  not to warm the soil.  

It would cost more for IBC containers for me.  The tubing is pretty cheap here.  Also the amount of tubing is determined by the size of the greenhouse,  so making a small system would seem to be easier all around.

Would certainly be interested in hearing more about the number crunching.

IBCs are expensive here too. I have seen pictures of them crushed by the earth when buried at surface, I don't expect they would fare better 9' down...

Beyond that, air is a terrible thermal storage/transfer medium, and plastic isn't the greatest either. I would think that surface area would be key to accessing the warming/cooling potential of the ground in a timely fashion... building up a larger reservoir of underground temp air is probably not very helpful relative to NC reading the rate at which you can heat/chill air.

By that metric you'd want max tubage. There would be a sweet spot for tube sizing below which you're restricting airflow too much, and above which you're spending too much money on diameter when more length would accomplish more.. but this would obviously be based on total length of each run, so parallel runs would seem preferable...


I plan to build something vaguely similar, but I'm tempted to use water instead of air. Groundwater is probably within 8'  even in summer, and in winter water collects just below surface where the clay starts... so I would have to keep my air ducting perfectly watertight or have it flood and shut down..

Dillon et al,

I plan to build something vaguely similar, but I'm tempted to use water instead of air. Groundwater is probably within 8'  even in summer, and in winter water collects just below surface where the clay starts... so I would have to keep my air ducting perfectly watertight or have it flood and shut down

This is simple geothermal, depending on your area you may need to go deeper (or have a longer circuit). As people have surmised, the contact area is the most important design feature. Air would not be my choice, as it would require much more surface area and time to gain or lose kcals of heat, and the tubes are prone to develop mold due to condensation. We have a geothermal loop for our home, and it is shockingly efficient once installed, you are basically paying for the pump to move water through the loop. As long as the loop flow can be kept laminar (no kinks or tight bends), it doesn't take much energy at all. Most of them are closed loops, meaning you would need to create a heat exchanger/radiator. I would think filling the loop with rainwater would be optimal to prevent scale. Maintenance is basically nothing.  

I really like the basic design, which could be done with the swedish skirt like Mike's greenhouse. If you really wanted to be crazy awesome and had the right soils, you could make a couple sandpoint wells right next to your greenhouse and use them for your loops. You would have to start the loop below your frost line, but one trench and it wouldn't need to be more than probably ten feet long if you could make the wells. Or you could drill the sandpoint wells and set the greenhouse over it if you aren't retrofitting.

Just a note, there has to be a loop into each well, I was having trouble drawing it and I have to get my carrots in today!

Tj Jefferson wrote:If you really wanted to be crazy awesome and had the right soils, you could make a couple sandpoint wells right next to your greenhouse and use them for your loops.

Hey Tj, are you saying to have several sand point wells and pump water out of several of them and push the "used" water down several other wells?  

You could do it as an open loop, but I'm proposing them as simply a way of getting a loop of conduit down to depth, one loop in each well. Closed loops need almost no maintenance because there is no mineral buildup. Depending on your soil you can often get them to 25 feet. If you had four wells, that would be 2x23x4 feet of heat sink (for a two foot frost line). Plus the temperature at the halfway point should be in the 50s summer or winter.

Then you have a circulating pump to keep it going through your heat exchanger.

To give you an idea, my entire house runs on 6 Amps, which includes the heat pump! My loop is about 2000 feet in length. So I assume you could run this on a very small pump.

Ok, thanks Tj.  I guess I don't see how you'd get a loop of conduit down a sand point.  Would it be a 2" pipe and you feed two 3/4" pipes down it with a pair of close 90's at the bottom?  Not sure if that would fit.  But if it did, then you'd be sending your water down through the water in the 2" pipe to transfer heat.  But I'd think that would just cool the 2" column of water and unless there is enough water transfer in and out of the well the water would stay cold.  Or am I totally misunderstanding the idea?..

Another thought would be to use an extendable hole auger to drill an 8" hole down 15' or more.  Then run a few loops down and up and back fill with muddy soil to get good contact between the pipes and the backfilled soil.

Mike, that would probably work too. Our clay is impossible to use an auger unless attached to a really heavy device. I've gotten the tractor about to China digging a couple feet for pilings. Any "well" you would drill you actually wouldn't case. As you mentioned that would defeat the purpose. I was thinking trash pump well cased with bentonite and said sand point. I think you can reasonably do a six inch hole.

I was thinking about doing some wells for waterers for the animals, and I was thinking about doing what Travis Johnson talked about with a geothermal tank heater. He is an evil genius.

Trace Oswald wrote:
Could you explain the past about the tubes under the growing zone in more detail?  
My understanding is that the tubes can be buried anywhere you like as long as they are 8 to 10 feet deep.
...tubing is determined by the size of the greenhouse

You are correct, the tubes can be anywhere and determined by the volume of the greenhouse.  Conceptually, I was placing them under the growing zone, but they can be anywhere.
Perhaps you all can all help me figure this out with more certainty.

Let me explain my approach and correct me where I am wrong.

I only have anecdotal information on the size of the tubing and logic.  
Russ Finch in one video states this is all high school physics.  LDSPrepper; he mentions that the length of tubing should be the volume of the GH divided by 10 for 6" tubing.  Another misc. source says the air change needs to happen every 5-10 minutes.
I aggregated that information into needing 10% of the greenhouse volume in the air2ground heat exchange tubes.

A 17x80x12 greenhouse = ~12566 cft
The 6" tubing needed would be 1256.6 linear feet if you use LDSPrepper formula

Tubing 6" @100ft for ~$90 so $1170 for (13x100ft) tubing which provides (~19.63cft*13)  255.19 cft of exchange tubing or only 2% of the GH air volume.
To get to 10% of the GH volume I would need closer to 64 100 ft 6" rolls costing $5760.00.

I found 275 gallon IBC containers with cages $25-$30 used in various conditions which is 36.76 cft. which seem to be the more cost effective option if 10% of the GH volume is indeed needed for air exchange.

(The variations of using IBC containers is many.  Packed dirt could be between the containers and plywood placed on top with drainage tubes connecting each container.
The idea of biocement (calcium carbonate microbes) also seemed like an interesting option to create a cavern space if it is cheaper than cement or permitting issues arise.)

The main sticking point here is how much volume is needed to proper heating cooling air exchange.  
The specifics of ibc containers and their interface to the ground heating effect has potential if needed as the air does not strictly need to be in the plastic containers, merely a surface area to allow air to contact ground temperatures.

I think the gold standard (or at least silver standard?) for calculating tubing for a system like that is this Calculator from Eco Systems Design.  I think it could be the SunnyJohn calculator that was circulating a few years ago.  I thought most systems used 4" tubing which is much cheaper (but obviously smaller).

A 275 gallon IBC is probably about 36×44×40" on the inside.

That gives it a surface area of 9568 square inches.

A 6" nominal ID cylinder of the same volume would be  2246.7 inches long. Surface area 84925 Sq in.

For 4", 5055" length yields a surface area of 127000 Sq in.

This seems pretty significant to me... you could store a lot of cool air, but I can't see that there will be anything like enough time for it to cool back off once it's circulating.

Dillon Nichols wrote:A 275 gallon IBC is probably about 36×44×40" on the inside.

That gives it a surface area of 9568 square inches.

A 6" nominal ID cylinder of the same volume would be  2246.7 inches long. Surface area 84925 Sq in.

For 4", 5055" length yields a surface area of 127000 Sq in.

This seems pretty significant to me... you could store a lot of cool air, but I can't see that there will be anything like enough time for it to cool back off once it's circulating.

275 gallon IBC is  48×46×40" around the perimeter with the cage.
The bottoms could be cut out.
Hot air rises, cold air sinks.
The trench floor is the surface area in this case and the IBC containers merely cavern baffles.
If used as bulkheads in rows and columns with tubing connections, the insulation of air outside the plastic container and against the trench walls might very well work against the desired effect.

That was the reasoning anyway.  Measure twice cut once.

I acknowledge surface area was only being considered in hindsight as I wrote my response.  

Thanks mike for the calc sheet.

My apologies. Someone presented him in the first post on this page. [Bows deeply so no one can see red face]


I haven't read the whole thread so I don't know if this guy's ground source greenhouse has been discussed.

Nebraska retiree uses earths's heat to grow oranges in snow

https://www.youtube.com/watch?v=ZD_3_gsgsnk

Lots of useful links from this google hit for "nebraska greenhouse oranges".

https://www.google.com/search?q=nebraska+greenhouse+oranges&oq=Nebraska+greehouse+&aqs=chrome.1.69i57j0l5.13001j0j7&sourceid=chrome&ie=UTF-8

Interesting idea to use IBC totes, rather than drain tile.
It's like a rocket mass heater using a bell rather than ducts buried in benches.
Following that logic,  perhaps blue plastic barrels,  split lengthwise and laid cut side down, could offer the  air to ground surface area needed.

As I mentioned  before, the amount digging needed for these systems could be a real issue.
I find digging a wider hole or trench easier than digging a slit trench, as I can maintain the same distance from the work face,  instead of bending further and further over.
This makes the barrels even more appealing, requiring a two foot wide trench, just wide enough to stand in.

The difficulty of hand digging  long/deep trenches,along with the challenges of subgrade insulation   has me favoring above ground growing  beds as thermal mass.


Each day's  peak daytime tempatures are probably all you could capture with an above ground air to earth  solar thermal storage system,.
With a much smaller mass and no long deep runs of pipe , you couldn't store months worth of energy or tap the earth's ambient heat, but it could be much easier to build.

William Bronson wrote:Interesting idea to use IBC totes, rather than drain tile.
It's like a rocket mass heater using a bell rather than ducts buried in benches.
Following that logic,  perhaps blue plastic barrels,  split lengthwise and laid cut side down, could offer the  air to ground surface area needed.

As I mentioned  before, the amount digging needed for these systems could be a real issue.
I find digging a wider hole or trench easier than digging a slit trench, as I can maintain the same distance from the work face,  instead of bending further and further over.
This makes the barrels even more appealing, requiring a two foot wide trench, just wide enough to stand in.

The difficulty of hand digging  long/deep trenches,along with the challenges of subgrade insulation   has me favoring above ground growing  beds as thermal mass.


Each day's  peak daytime tempatures are probably all you could capture with an above ground air to earth  solar thermal storage system,.
With a much smaller mass and no long deep runs of pipe , you couldn't store months worth of energy or tap the earth's ambient heat, but it could be much easier to build.

I had and idea of building it over a cave.    Replace the IBC with a cave and you would have huge amount of air to cycle.

Mart Hale wrote:

I had and idea of building it over a cave.    Replace the IBC with a cave and you would have huge amount of air to cycle.

That is the gist of the design...  The IBC cages just provide a structural framework for the cave.

Dillon Nichols wrote:
For 4", 5055" length yields a surface area of 127000 Sq in.
This seems pretty significant to me... you could store a lot of cool air, but I can't see that there will be anything like enough time for it to cool back off once it's circulating.

You potentially get the sq inches equal to the trench floor which often is the sq footage of the greenhouse.
This IBC approach could even tap the sidewall surface area.
There are still design problems with this but the potential is there and the cost is competitive.

Dillon touched on something that I think may be critical to this.  "I would think that surface area would be key to accessing the warming/cooling potential of the ground in a timely fashion... "  

This is all conjecture on my part, but I'm wondering if the greater air volume to surface area ratio in the IBC wouldn't cause a problem.  This may be completely wrong, but I'm picturing a scenario like a car radiator that had all it's baffles removed, or was simply replaced by a metal box with the same outside dimensions as a radiator.  The surface area would be cut down so much in relation to the amount of water, the water wouldn't be cooled much before it circulated through.  I'm picturing the same thing in reverse with the IBCs.  I'm not sure the surface area touching the air would be enough to warm it before it was circulated back into the greenhouse.  

Trace Oswald wrote: This may be completely wrong, but I'm picturing a scenario like a car radiator that had all it's baffles removed, or was simply replaced by a metal box with the same outside dimensions as a radiator.  The surface area would be cut down so much in relation to the amount of water, the water wouldn't be cooled much before it circulated through.

Yes this approach does present many practical problems.  (Forgive me for entertaining possible solutions to those problems as haphazard and half-baked as they might be.)

Rebar comes to mind, it adds to over all costs but it could provide the same function as the radiator baffles...  
Re-purposed Tin Siding could be an effective solution.  
Mini ground trenches was my immediate solution they mostly cost labor.  
If there are enough rocks in the excavated ground rocks in the first few inlet IBC's could create extra surface area to pass air through till it hits the ground floor.  
Or the inlet IBC could spill air out the top that drains down the sides and travels back over a rocky bottom ground surface.  
Subterranean precision engineering seems a little to risky at this point.

Granted, just dropping drainage pipes into the ground seems like the most time cost effective solution.

James Rubino wrote:
Yes this approach does present many practical problems.  (Forgive me for entertaining possible solutions to those problems as haphazard and half-baked as they might be.)

Rebar comes to mind, it adds to over all costs but it could provide the same function as the radiator baffles...  
Re-purposed Tin Siding could be an effective solution.  
Mini ground trenches was my immediate solution they mostly cost labor.  
If there are enough rocks in the excavated ground rocks in the first few inlet IBC's could create extra surface area to pass air through till it hits the ground floor.  
Or the inlet IBC could spill air out the top that drains down the sides and travels back over a rocky bottom ground surface.  
Subterranean precision engineering seems a little to risky at this point.

Granted, just dropping drainage pipes into the ground seems like the most time cost effective solution.

Rocks large enough to have lots of airflow gaps seem like a great way to gain surface area.

I think getting pretty deep is also important. I don't know if 10ft is really needed for everyone.

I have used a 2ft deep hole with 1ft board sides above as a minigreenhouse for plant propagation; sized it to use a sliding glass door for a lid. It worked very well, much less watering needed and improved success rates vs regular greenhouse... BUT to avoid overheating I placed it directly on the north side of a shipping container. It would have been useless for season extension as the thing would see no sun from fall to spring.

James Rubino wrote:

Trace Oswald wrote: This may be completely wrong, but I'm picturing a scenario like a car radiator that had all it's baffles removed, or was simply replaced by a metal box with the same outside dimensions as a radiator.  The surface area would be cut down so much in relation to the amount of water, the water wouldn't be cooled much before it circulated through.

Yes this approach does present many practical problems.  (Forgive me for entertaining possible solutions to those problems as haphazard and half-baked as they might be.)

Rebar comes to mind, it adds to over all costs but it could provide the same function as the radiator baffles...  
Re-purposed Tin Siding could be an effective solution.  
Mini ground trenches was my immediate solution they mostly cost labor.  
If there are enough rocks in the excavated ground rocks in the first few inlet IBC's could create extra surface area to pass air through till it hits the ground floor.  
Or the inlet IBC could spill air out the top that drains down the sides and travels back over a rocky bottom ground surface.  
Subterranean precision engineering seems a little to risky at this point.

Granted, just dropping drainage pipes into the ground seems like the most time cost effective solution.

The difference I see with IBC verses the pipe is the turbulance created by the air against the sides of the pipe.        

I think I would approach it like a rocket Bell, I would figure on stratification of the air in the IBC's, so Hot air to the top of the IBC  and cold on bottom,  unless the air exchange prevents stratification by all of the movement.

here's a few links from PRI  

https://permaculturenews.org/2015/12/16/grow-your-own-food-year-round-with-diy-solar-greenhouse/

one alternative

https://permaculturenews.org/2014/10/18/canadian-rocket-stove-powered-greenhouse/

rocket stove alternative

https://permaculturenews.org/2011/02/11/how-we-designed-our-solar-greenhouse/

Calgary Canada example

The link I was looking for (and haven't yet found is a Geoff Lawton video tour of a similar greenhouse in Canada.
For simple termal battery- ie not just the normal ground heat, but increased by solar inputs, remember the perimeter insulation about a meter deep--or at least as deep as the tiles are buried

I'm also looking at cutting blue barrels in half for an earth tube for air conditioning in summer, but trying to think of ways I might tweak it to provide heat in the winter.

BTW, at a meter deep, blue barrels might not be strong enough for driveways, so I plan to use the regular septic chambers which are designed to carry a dump truck weight wherever necessary.

I’ve been kicking around the idea of doing one of these on our field. Digging isn’t much of an issue as we are all sand covered in silty/sandy loam, but I am somewhat nervous about mold developing in the geo tubes over time that would be almost impossible to remediate. Mold has been discussed elsewhere but I haven’t seen one of these greenhouses being built in the humid northeast and if that would affect any mold development issues.

In any event we plan to go forward with a sunken greenhouse backed by a northern wall made of sandbags. One variation we are considering is in the center of the sandbag wall building an underground vault chamber that runs towards the north that could be used for storage, basically forming a T, the top of which would be the sunken greenhouse.   The underground portion would in our design be roofed by steel culvert pipe assembled on walls on either side of the vault. These culvert pipes come in a wide variety of sizes and strengths, from tiny to massive. The vault would have a hobbit  entrance at the northern end and the place where it meets the sunken greenhouse

The underground vault could be used for storage, an office or even for habitation. We are thinking a rocket stove placed at the juncture of the vault and the greenhouse would be sufficient for heating the entire space. One idea is to reserve pathways in the field for future installation of geo tubes if we decide to add them.

I had looked into the issue of mold as well when considering my earth tube, and it started to look like the issue would be less problematic in a tube exposed to the earth.  Not so much that there wouldn't be any mold, but more that there would be enough competition to keep truly unhealthy organisms from gaining total control.  I wish I had kept those links that led me to that thought, but it was done some time ago and i figured I would have to do a more complete study later

When asked about using plastic tubing, Bill said something to the effect of preferring sides and floor be earth,whether he was thinking about mold or expense (or both) is difficult to say

Of course the other way to think about it might be that the tubes will create that mold prone environment, and design in some living feature to occupy that niche to prevent any harmful mold growth. (I don't have a clue off hand what that might be)

bob day wrote:I had looked into the issue of mold as well when considering my earth tube, and it started to look like the issue would be less problematic in a tube exposed to the earth.  Not so much that there wouldn't be any mold, but more that there would be enough competition to keep truly unhealthy organisms from gaining total control.  I wish I had kept those links that led me to that thought, but it was done some time ago and i figured I would have to do a more complete study later

When asked about using plastic tubing, Bill said something to the effect of preferring sides and floor be earth,whether he was thinking about mold or expense (or both) is difficult to say

Of course the other way to think about it might be that the tubes will create that mold prone environment, and design in some living feature to occupy that niche to prevent any harmful mold growth. (I don't have a clue off hand what that might be)

I was thinking ozone mixed in the air as one idea.     another idea I had was an heat exchange,   not letting the indoor air mix but creating a loop where the condesation would be in the greenhouse alone.

I bought the plans he has and I have a few tubes,  I have been wanting to do an experiment with a small box and put the pipe at different depths to see what makes the most sense here in Florida.

Russ says he has had no mold issues in his installations.

bob day wrote:I had looked into the issue of mold as well when considering my earth tube, and it started to look like the issue would be less problematic in a tube exposed to the earth.  Not so much that there wouldn't be any mold, but more that there would be enough competition to keep truly unhealthy organisms from gaining total control.  I wish I had kept those links that led me to that thought, but it was done some time ago and i figured I would have to do a more complete study later

When asked about using plastic tubing, Bill said something to the effect of preferring sides and floor be earth,whether he was thinking about mold or expense (or both) is difficult to say

Of course the other way to think about it might be that the tubes will create that mold prone environment, and design in some living feature to occupy that niche to prevent any harmful mold growth. (I don't have a clue off hand what that might be)

Most molds should not be an issue if there is no organic matter for it to feed on.

OK, we are starting to put together the greenhouse. See it HERE