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Earth Tubes: A Natural Way to Air Condition Your Home

There is nothing nicer than coming inside on a hot, muggy summer day to feel the freshness of an air-conditioned home. Traditional air conditioners, however, are one of the most energy-intensive appliances in our homes. Only a couple feet underneath where you are standing, however, the air is always a comfortable 55 degrees Fahrenheit. If only it were possible to get that cool air from underneath your feet into your blistering hot home. Earth tubes offer a natural, ecologically sound air conditioning option to keep your home cool on even the hottest summer days.

How Much Energy Does Your Air Conditioner Consume?

As with a number of aspects of our modern-day industrial civilization, we simply don´t know or understand the ecological costs associated with the comforts we have come to depend on. In many ways, ignorance is bliss and it is comforting to naively believe that a cool home on a hot summer day is a normal part of the landscape.

The distance between consumer, the origins of his or her consumption and the end place of his or her wastes facilitates this obliviousness to the true effects that our industrial lifestyles perpetuate. Unless you live near a coal burning plant in Kentucky or have nuclear waste buried beside the gravesites of your ancestors in Arizona, you probably have little actual connection to how the electricity your home uses is supplied or the end product of that energy.

The cool air that dries the sweat from our foreheads, however, is far from inoffensive. While some small, window-based air conditioners consume up to 500 watts, a large central air conditioning unit that many large homes and almost all businesses have is easily a 3500-watt appliance.

While you can cut back on your ecological footprint by trying to occasionally open windows or turn the thermostat a bit higher, the fact of the matter is that because most modern-day homes are so poorly designed, chances are that your home could resemble a small oven if you try to turn the air conditioner off. In recent years, heat waves have swept across different parts of the world. The summer of 2003 in Europe was one of the hottest summers on record. In Spain alone, over 140 people died as a result of the heat, mostly elderly people who were stuck in homes that heated up like ovens.

If the modern-day housing and construction industries embraced ecological design principles, much of the potentially dangerous heat from the summer sun could be avoided. Passive solar design makes it possible to block the hot sun from the summer months while allowing the winter sun to enter the home and add needed warmth. Unfortunately, the first step of most home construction is to level the site and clear any trees or vegetation that are “in the way.”

The Coolness of Caves

If you have ever spent time exploring a cave, you might have noticed that caves always seem warmer than the outside temperature during the winter and cooler during the summer. The actual temperature of caves depends on the average annual surface temperature of the place where they´re located. Carlsbad Caverns in Texas has an average temperature of 70 degrees while Crystal Cave in Wisconsin averages a much cooler 49-50 degrees. Might it be possible to move that cool air from underneath the soil into your homes to provide an alternative source of cooling air?

What Are Earth Tubes?

Earth tubes, also known as ground coupled heat exchanger systems, aim to take advantage of the cool air beneath your home to keep your house comfortable during even the worst heat waves.

As we mentioned above, the temperature of the ground just a couple of feet beneath our feet is a usually a comfortable temperature anywhere between 50 and 70 degrees Fahrenheit. While some ground coupled heat exchanger systems involve complicated pumping of water throughout the system of tubes, a simple earth tube system simply requires plastic PVC plumbing pipe, and a small fan.

The entrance for the earth tube system is a piece of pipe that sticks up out of the ground somewhere outside your home. A minimum of 100 feet of pipe is buried several feet underground until eventually passing underneath your home foundation and into your home. You can then branch these tubes in several directions so that the tube system exits into different rooms that you want to cool during the summer months.

A blower is situated at the entrance of the earth tube system to move the air through the piped system and into the home. By burying a long portion of plastic tube underneath the ground, the cool temperature of the soil is exchanged with the warmer air that is entering the tube. Over the course of the 100 feet of pipe (or more) the air, through the physics of heat exchange, becomes cooler as the surrounding soil gets minimally cooler. The result is a comfortable flow of cooler air that enters your home without the aid of any sort of chemicals, compressors or fossil fuel dependent central cooling systems.

How to Install a Natural Air Conditioning System in Your Home

The exact specifications for your earth tube air conditioning system will depend on the specific climatic context where you live. If you live in Maine, for example, the average temperature underneath your soil will be much more pleasant than if you live in southern Florida.

As a general rule, the cooler your average annual surface temperature, the less amount of piping you will need. Since the temperatures of the subsoil will be cooler, you will also be able to get away with not burying your piping too deep. In the case of most cool weather climates, a two-foot depth should be more than enough to reach an optimal soil temperature to cool your home.

If you live in warmer climates, it is advisable to bury more pipe (between 150 and 200 feet) and bury it deeper. You may need to invest in a more powerful blower for the longer your piping.

Once you have your pipes buried, it is important to consider exactly where you want the cooler air to enter your home. The south-facing side of your home is where you will receive the most heat from the sunlight, and is a good candidate for at least one exit for your earth tube system.

Using the Earth to Cool Your Home

Why would anyone choose to cool their home with fossil fueled powered air conditioners when an infinite source of cool air is just below their feet? While remodeling an existing home for an earth tube cooling system could be expensive due to the digging and opening holes in your floor and foundation, the savings (both economic and ecological) will last a lifetime.

Tobias Roberts

After working in the development industry for over a decade, Tobias decided it was time to stop advising Central American farmers how to do things if he didn´t have a piece of land to live coherently with what he taught. Together with his family he runs a small agro-forestry farm, tourism cooperative, and natural building collective in the mountains of El Salvador.

57 Comments

    1. That’s right, and the writer could also have found out with a simple WWW search that the average temperature is not 70 but 56 degrees F.

    1. It is necessary to have a pipe with a small outlet pipe for the condensed moisture in the pipe. For this to drain a slope is usually required. My partner Phil Baulch from Python Solar Heating & Low energy Cooling installed a system like this at Mildura Eco-Living centre, several years ago.

      1. I don’t think a drain pipe will suffice to prevent mold. I would use a stronger fan and put HEPA filters at each outlet

    2. If you pass the cooled air through a mass like a rocket stove uses in your house then you get a cooling mass rather than dealing with the mold or radon issues. I read about a design that uses concrete culvert pipe so there is plenty of airflow and it dehumidifies the air in the tube as it leaves water on the surface by condensation and serves as its own drain to the outlet somewhere down hill. This chimney can also be used as a dehydrator which is great for tropical areas. Yes underground it was on a slope to drain and connected up to an even larger mass chimney for heat transfer from the home to the chilled stone. The chimney was dual purpose allowing fire exhaust for cooking, also using the outside air for draft so as not to draw conditioned air from the house.
      .

      1. I really like the idea of having a cooling mass. Perhaps pipes could be run through the floor on their way to the rocket mass bench. The chimney could provide a draw to pull air through rather than having to blow it–the hotter the day, the more the chimney would heat and the greater the draw (perhaps a black metal pipe could sit on top of the chimney to increase the effect).

  1. I remember reading about these many years ago in popular science magazine and if I recall correctly there is a rough calculation for how many square feet your house is to the diameter of the tubes and length of tubes. you wouldn’t buy any chance know where to find that calculation would you?

  2. While an enticing idea, I am leery of the actual results. Tobias- have you actually done this, or know anyone who has? And how were the results? I would think a couple hundred feet of plastic pipe would quickly warm the surrounding soil, ending the cooling effect. Heat transfer through soil takes time, and the number of air exchanges to cool a house is a large number. Also, what happens to all the condensed water inside the pipe? Mold. And if you try to provide a drain, where to drain to? You are already underground. This article is just feel good fluff if it doesn’t address real world practical details.

    1. The writer says “Over the course of the 100 feet of pipe (or more) the air, through the physics of heat exchange, becomes cooler as the surrounding soil gets minimally cooler.”

      This is nonsense, of course. I think “fluff” pretty well describes the article.

    2. I am doubtful the surrounding soil would warm much, since it is constantly being cooled by all the soil below and around itself. The fact that 50 cm down it is so much cooler than the surface indicates how little the heat from the sun and air penetrate the soil in spite of a constant heat difference.

    3. I believe the Earthship type homes use this concept of a pipe from outside being buried in a large mass of earth so that the hot air of the desert is cooled as it exits into the house. The system looked static to me, that is, no far to move the air, just selectively opened windows on the sunny side of the house. And it seems their homes stay a cool 68-70 degrees.

      1. We just stayed in an earthship and it is a tube covered in earth. You open the door to the tube. Crack a window on the south facing wall. That’s it the heat leaving the window pulls cold air from the tube through the house. It kept the house around 68°

  3. Steve makes a good point. Cooling the incoming air will warm the soil. If the system is designed properly this can be an advantage in a temperate climate. The incoming air can be warmer than the average soil temperature in the winter and cooler in the summer.

    John Haiti wrote a book called Passive Annual Heat Storage (978-061590588-4). In the book he describes a house he built that uses a similar system. His system is driven by convection currents instead of a blower. So, it really does not use any fossil fuels.

  4. What about Radon consideration?

    Will this type of system be sucking up and blowing Radon into the home?

    1. I don’t think radon would be a concern, since the air intake is simply outside air–you are passing the air underground, but, at least if the pipe is sealed, you would not be picking up underground gases.

    1. studied with Bill Mollison in 1995
      retired Landscape Architect in California
      now living in 30′ diameter yurt on sloped property
      yurt facing south, hot in summer
      thank you for pertinent info sources

  5. Digging a straight column can be done through hand-powered percussion drilling, and is not that difficult. It helps to have a group of people to work on it, and you can get 100 feet in a few days, then pass the equipment on to another person. The equipment can be hand-made by scrap metal by a blacksmith in non-industrilalized regions. https://www.wellspringafrica.org/drildesc.htm.

  6. This is not as simple as it sounds. First, if the temperature is the same all year round, that means that the earth is acting like a very good heat insulator. If the earth is acting like a good insulator, then it will be heated by the hot air flowing through the pipe. Second, I see the blowers that run forced air heating are about 500 watts. It would take even more to run air through a long 4″ pipe. It would be better to have many shorter pipes in parallel than one long pipe.

  7. When purchasing another ventilation system, think about the span of the room. A unit too little for space should run always yet one too huge will keep running in short cycles, causing additional wear and tear.

  8. Yes Wendy, you generally need to have a uniquely positioned house to enable this to work, as I do, with the house built on the a slope with the garden area at the top – then a condensation drain can run along the side of the house and come out into the garden down the slope. Otherwise, some form of sump and pump is needed.

    1. It sounds like you set up your cool tunes to terminate below you. So the air is forced up into your building ? I see the benefit for drainage to do it this way. But since cool is heavier I wondered if I should set up my inflow uphill from my cabin of 400sq’

  9. I see no mention of humidity. I can’t see this kind of system working at all across the southern part of the United States, especially in the high humidity coastal areas. I was in Natural Bridge Caverns near San Marcos, Texas a number of years back. I remember it being cool down in the cave (70 degrees F), but the relative humidity was 99%, so it felt hot. Of course, on the surface, the humidity won’t be that bad, but cooling the air to 70 degrees F without ridding the house of high humidity will lead to uncomfortableness in the house. I purchased a dehumidifier for my house a few years back, but the thing emitted hot air, thus heating up the house. If I had expelled the hot air outside of the home, humid air would have been sucked in in various places to replace it. This system seems suitable only for low humidity areas in the top half of the United States.

    1. How about a whole new take on this. What about a supercharged architectural pergola absorbing all the heat above and around a home. Use your imagination for additional functions.

  10. I remember in the 1970’s the idea was called Mexican Cool Tubes. I think it was noted in The Whole Earth Catalogue but can”t be sure of this.

    I have heard of treating the inside of the cooling pipes with colloidal silver to minimise bacteria and mould.

    Assuming that there will be some condensation from the warmer moist air nearer the entrance of the pipe where there is a temperature gradient and the condensate flows down an inclined pipe past a point where there is no longer a temperature gradient, would the passage of the air over the condensed water of the same temperature cause it to slowly evaporate again minimising the need for draining the system?
    Perhaps it depends on the length of the tubes. The longer the tube the better chance of the condensate evaporating again.

  11. I am interested in building a Wallipini attached to a small garage (attached to my home) and have been considering some kind of ground coupling heating and cooling for the Wallipini. Could piping ruin under the slab of the garage and into the Wallipini act as a heating mass in winter and cooling mass in summer? My idea is to bring a pipe up to near the peak of the wallipini that could draw the hot air into the earth mass under the slab during the hot months and push cooler air into the wallipini so it wouldn’t get too too hot. In Winter the air flow could be reversed.

    Insulation a few inches under and a foot or two above would help keep the heat in the earth mass under the garage slab.

    Thoughts on whether something like this might work here in Maine?

  12. Introduce the cooled air into a mechanically shaded Thromb wall.
    Most bars in America have air filters that add and atom of oxygen = H2O2, it kills bacteria. This system works very well in the winter.

  13. In Sebring Florida the night temperature is a good 6 degrees cooler than 90 minutes to the south or nearby coast. I’ve noticed this 6 degrees makes a big difference for trying to sleep in a van at night without air conditioning. It seems to be even better when you park out in the woods over sandy soil away from pavement and buildings. .. Ive also noticed very simple things like using well water over, under and next to my van after the sunsets makes a difference… So I was wondering …if drive an 8inch x 10′ pvc pipe deep into the ground and flushing out the soil knowing the bottom will fill with cool well water. Will blowing air in this pipe and up into my van will make my a noticeable difference in cooling a 50sqf van?

  14. I’m building an off-grid passive home in Northern Ontario. Under the slab I have 900 cement blocks lying on their side so the holes line up. A few vents through the slab at the south side of the house and a few at the back create a convection air flow from the north side (cooler air), under the slab through the block holes to the south side. Windows on the south heat the slab that heats the air in the blocks under the slab, the warmed air flows up through the south vents and cooler air is drawn down into the north vents. The whole slab gets evenly heated during the day and a fan helps distribute the heat at night. In the summer the under slab blocks are used for cooling.

    The home is approximately 2000 sq.ft.. The walls are R40+ and the roof is R60+.

  15. Check out greenhouse in the snow on utube. We just installed this geothermal heating and cooling system in our backyard for our greenhouse. We used 10, 250 feet perforated drain tile tubes in a 9 foot trench run in one end and back around to the other end of a 60 foot greenhouse. There’s more details to the system but too much to list. This concept most definitely does work however for being used in the home I would be worried about air quality. The concerns of mold drainage radon and particulates are my concern and would need to be addressed before I felt comfortable doing this for my home.

    1. Why perforated? Perforations definitely allow for Radon infiltration – that’s how radon evacuation systems work. Seems to me a thinner-walled solid pipe would be most effective. (Something thinner than schedule 40 pvc)

  16. I love how a bunch of “experts” come on here and start criticizing someone who actually got off their a$$ and did something for other people, and free at that. Ill bet not a single person who posted on here has any idea what they are talking about and cant back any of it up with common sense or foundationally solid information. Anyone can Google anything and come on here and regurgitate what they see so they sound so smart and sophisticated. Truth is, you are miserable people who are in need of constant psychological validation. This is whats wrong with the world today, its sociopathy is a borderline epidemic.

    How about just saying, “Hey, thanks for taking the time out of your life to write the article. It gives me some great ideas!” No, you have to come on here and pi$$ and moan and show everyone how big your w3iner is. Its pathetic.

    Ill just say thanks to the author, gives me some great TANGIBLE ideas that I can actually see through to fruition…unlike some people on here.

    Morons

    1. Thanks Murray for your “voice” delivering my conclusions upon reviewing each of these Posts.

      My Mennonite building partners & I built 33 of these for residential use in the SE, along the Western TN/KY line. Thousands of Caves in the region making general knowledge of the concept readily understood.

      As stated above, MOLD is the Primary concern. Weep Holes reduce standing ‘water”. A RAG DRAG performed at least every 45 to 60 days is a MUST, in the SE ONLY. For the desert climes the rag drag is employed twice a year IF the Tube is employed as an A/C ONLY. More often during colder season which coincides with the rain season, hence greater level of condensation being passed thru the tube.

      RAG DRAG: Metal Cable is laid within your chosen pipe from end to end. At 1 end a “rag” is attached. At the other end is a loop used to grab & pull the “Rag”. The rag is covered/sprayed/dipped in a off the shelf cleaner or homemade. Is greater detail needed. At this point imagination & your preference is all U need.

      All of ours are at a min. Of 75 feet long. Max: 125. $” to 6” diameter. Initially we used schedule 40. Quickly evolved to thin wall sewer blue/green pipe.

      Currently (July 2022): trenching 3ft deep with 2 layers of insulation board touching top of pipe. 118’ in length with two 45s. Definitely prefer a 48” depth minimum BUT . . . That equipment is all but non-existent & the wait time (on a existing list!) is another 4 months. Screw that, lets rock n roll. Have not set in stone the blower make or volume. Will test different makes/configurations & volume levels. Definitely including charcoal at both ends as well as air filters. Almost 4got: 25 feet will be under a 4 ft deep body of water (partial above ground pool). Again . . . Use your common sense as to the result of this inclusion.

      We R located in the SW corner of Riverside County California.

      1. I’m in Arkansas and would appreciate all the information you are willing to share. Hubby and I are considering DIYing a system like this, temp. Today 7/16/2022 was 102*f, … considering 4-5ft deep for pipe, 2 story house, would heat out from top of second floor, and cool in on ground floor and house is on Pears..

      2. Thank you so much, Steve.
        The Rag Drag was a confirmation of my own thoughts about how to keep the air clean and healthy.
        Please come back and share links where you can be found to learn more about your experience in doing this.

    2. Could not agree more.Great starting point. I got some great ideas from the information shared.

  17. i m considering a system like this for a 100 sf cabin in TN hills. Im thinking run tube from interior of house as air entry and the other end as AC exit . In other words recirculation. running on a down slop digging a 1,5 by 1.5 hole mid way and lining with sealed brick having piping end at one end and pick up at other allowing moisture to drop into trap and drain out via drain tube. Lining the brick with stainless steel completely. with a filter (With ability to be changed )on the exit side.

    Does it sound doable? Is there a reason I wouldn’t want air recirculation? Please only helpful answers.

    Thx

  18. Thank you for sharing this insightful article! It highlights the ecological and energy consumption issues associated with traditional air conditioning and presents an intriguing alternative with earth tubes. The idea of utilizing the naturally cooler ground temperature to cool homes is both innovative and environmentally friendly. It’s a great reminder of the importance of considering sustainable solutions for our modern comforts.

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