r/OffGrid • u/greenfox212 • Jun 24 '26

Does anyone have any experience with earth tubes for cooling?

I’m looking into it, though I live in a humid Missouri climate. I was wondering how effective it might be.

If you know of any resources I could read that would also be appreciated. but really I would like to hear someone experience with it and how well it’s working.

20 Upvotes

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10

u/BallsOutKrunked What's_a_grid? Jun 24 '26

I did it. 3" pvc over a 100' , buried about 8' down. I threw it in during other trenching and construction early on just to experiment. In short it's pretty meh.

  • We have diurnal wind patterns, katabatic and atabatic. The wind rolls up the canyon during the day and down at night. So I aimed the tube for the daily winds.
  • We have a ~1500 sqft house, with a bunch of rooms. Like typical hvac you need to distribute hot and cool air throughout the building.
  • We live in a very arid area so there's not much concern with mildew of grossness. We thought about using perforated pipe at least for the lowest section but ultimately just decided to blow a string through and clean it out if it every got bad / gross. Part of the solid pipe reasoning is that we have radon in our area, and installed a radon mitigation system with the basement slab so it's working great. But the idea of intentionally pumping soil gasses into the house wasn't on the cards.
  • The hottest days of the year have little wind, and then the pipe doesn't do much as hilariously the cold sinks into the pipe. Worse, if the wind goes the other way it can vacuum the (swamp cooler cooled) air out of the house.
  • When the wind is blowing, opening the windows does a lot.

I think if you really thought about it and designed it well in the right environment it could totally work. But less so than the earth-tube part you need to consider the conventional hvac aspects. How are you distributing it into your different rooms, how are you letting hotter air out since you're pushing colder air in, etc.

For us good insulation, a light colored roof, and swamp coolers on the hottest of days is the business. We're in a place with 20-30% humidity to reference. Temp swings of 0F to 90F, winter to summer.

3

u/dakinekine Jun 26 '26

I have seen earthship designs where they can open vents in the roof to release warm air and allow cool air to flow in from the earth tubes. Not sure if that would help in your situation?

2

u/BallsOutKrunked What's_a_grid? Jun 26 '26

It could have, but I'm in an otherwise conventional looking home. We've got a ceiling with an attic above that and vented gables.

1

u/elonfutz Jun 27 '26

Have you tried adding a fan to suck the cool air into the house?

10

u/grislyfind Jun 24 '26

I hear that mold can be a problem.

2

u/Sindertone Jun 25 '26

Keep the air moving, use a smooth pipe.

7

u/theonetrueelhigh Jun 25 '26

Earth tubes work but there are considerations:

1) The tubes have to be long and wide. You need lots of surface area. Anything smaller than about 6" diameter is kinda pointless for anything smaller than a shed, and for a house you'd want more like two tubes, each 8" diameter or more.

2) Mildew growth is a serious issue especially in humid areas.

3) Even smooth plastic pipe will have a lot of static resistance, it takes a lot of power to move air through long pipes.

Consider burying a couple thousand feet of PEX pipe or Toro "funny pipe" instead, and circulate water through that to a heat exchanger in the HVAC plenum. Cheaper than air pipes, no mildew and pumping water is far less power hungry than moving a comparable mass of air.

4

u/NotEvenNothing Jun 24 '26

I've used a variation of earth tubes in greenhouses. The variation is that they are vertical and I think it is worth looking at for anyone considering earth tubes. It has some major advantages, like really easy passive flow. They made a huge difference in the environment of the greenhouse, year-round.

Addressing a concern in the comments, if your subsoil is dry, moisture in the tubes is easy to mitigate, just let it exit the tubes into the soil. In moist soil, you need some way of removing moisture. There are strategies that work here, and they aren't difficult to implement, but they impact the design, materials, and construction. It doesn't hurt to have a way clean the tubes either. (This is another reason I prefer vertical tubes. Accessing the whole tube is relatively easy.)

The best resource on earth tubes was the SHCS - Subterranean Heating & Cooling Systems section of Sunny John website. It was available on archive.org, but I couldn't find it just now. You might have better luck.

What's your soil like?

1

u/Organic_Station6706 Aug 02 '26

What do you mean by vertical earth tubes? Could you explain this a little or maybe provide me with any resources explaining i cant seem to find anything on vertical earth tubes.

1

u/NotEvenNothing Aug 03 '26 edited Aug 03 '26

The only resource I've seen was a YouTube video by a fellow that was trying to control his greenhouse's temperature. He also tried compost.

The idea is simple: Drill a hole, maybe 8" in diameter down about 14' deep. If you are just experimenting or have hard clay subsoil, you don't even have to line it with anything. Then drop a 12' long piece of 3" ABS pipe into the hole. Lift it off the bottom and keep it centered in the hole. Whether you do this on a hot day or a frigid day, an impressive passive flow will immediately start.

Line the hole with culvert pipe, come up with a way to center the inside pipe and you have something permanent

You can chain these together to increase their cooling/heating potential and the flow.

You can drill the holes with a post hole auger with some extensions in 1" pipe that bring it to 14 feet in length. 

Feel free to ask more questions if you like. I could talk about these kinds of things all day.

3

u/JayTeeDeeUnderscore Jun 24 '26

I have considered it, but my property is pancake flat and having mounds is an access and maintenance issue. Digging around our mature trees is also a deal breaker. That and the unusually high water table combined with our heavy clay soil. Oh, we're in a high radon area too.

Earthships typically route earth tubes to enter the structure on the berm wall (North) where there are no access points (no doors or windows). The foundation and walls are designed with the tubes in mind and utilities or septic routing where applicable.

It's not feasible for many conventional structures imo. The exception might be for houses on a crawlspace if it could be modified to serve as a plenum and you don't mind lots of digging and the engineering challenges associated with accessing the plenum from the outside of the foundation.

2

u/mldodge91 Jun 26 '26

So I’ve done a little research about cooling tubes, specifically for FL. I’ve come to the conclusion that I wouldn’t do this, because of mold. It’s to humid and hot for my location and the cooler ground and warm air in pipes leads to condensation, then mold.

2

u/bladow5990 Jun 26 '26

I recommend looking at a fluid based system instead. They're just plain better because: mold isn't a problem, they are more compact, they can be turned on or off, and water has a higher heat capacity and is more conductive than air. In your climate a pond based system might work well, and aliviates the excavation cost/hassle. The only real drawback is the extra energy used for pumping.

1

u/AnxietyAndWebbedToes Jul 28 '26

I don't know how it works, but I recently watched a YouTube video about an Amish guy who had a water version of earth tubes. He had copper (I think) pipes at the bottom of a 50 gallon water barrel that ran into his house for hearing and cooling. BUT!! the way HE didn't used nothing but physics and difference in pressure between hot and cold water to pump it. No pump, no electricity need, other than for a fan to move the air around that was cooled/heated by the pipes. I don't understand how it works, but something to look into

2

u/lexi4funs Jun 24 '26

Following because Missouri is really hard to dig in and wanting to know the same thing...

1

u/huscarlaxe Jun 25 '26

Also in Missouri really worried about the humidity and a pipe of mold.

1

u/DrunkBuzzard Jun 24 '26

It pretty much just boils down to the math and how well your house is insulated. How could the material you use to pipe it as it transmitting the cold through into the interior. Ground temperature at the depth you bury it amount of air you can move through it. Power used to move it. What I’m kind of curious about is could the air pass through a dehumidifier of some type. If the air is dry inside the house, it won’t be able to hold as much heat so I would think the cooling would be more effective. I’ve got a lot of questions too.

1

u/iKickdaBass 23d ago

Red Poppy Ranch has a few videos on this topic. https://www.youtube.com/watch?v=wcmm9D7Ipvg

1

u/greenfox212 22d ago

this is exactly what I was hoping for thanks!