Earth tubes

I’m trying to find a site that discusses alternative heating and cooling for a home in Florida, does anyone know of a forum site that can help me understand if earth tubes could work on a 900 sq ft home in N. Florida, I’ve spent 6 hours today with no success, sorry for asking since it doesn’t pertain to growing fruit.

Is this the kind of thing you’re looking for?

A lot of us here first met on the old GW site. It still has some good stuff even without us!

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I forgot all about that site since I found this site and for some reason that site never popped up in my searches today. Thanks.

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Most of the successful earth tube systems I’ve seen are in dry climates a solar water system might work for a mild climate

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I would be cautious about an earth tube type system in any climate, but especially in moist ones.

I do use an earth tube like system in one of my greenhouses, but molds are less of a concern there (and if I stop irrigating the soil is dry in just a couple of days in my dry climate).

Ultimately the limiting factor in any passive (vs heat pump) system is that the storage media (dirt in the case of earth tubes) heats up or cools down as you try to push/pull more heat to/from it and the transfer efficiency goes down. You can bury the tubes deeper and over a bigger area which helps some, but ultimately the long term efficiency degrades. Not much you can do about that as eventually the storage media will approach your air temps. Even when your “transfer location” is at a point of constant temp, it takes some time for the temp anomaly the system creates to equalize.

For a home, I think the newer heat pump systems may be a better choice. First, their air ducts are not underground and so molds from underground air passages are not an issue. They also can be designed with air to air or air to ground (with a fluid going underground); and efficiencies have improved in recent years.

Just my 2 cents on this.

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We’ve had a ground source heat pump for 10-12 years or so and it’s done well. Our ground water is not too deep and we have an open loop (i.e., less than optimal) system. We had a well sunk and it has made irrigation really cheap too. But a closed loop system would be a lot better- just not particularly feasible in our situation.

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I was wondering if a closed system would work like the sketch attached, it would only be used 5-7 months for cooling the hotter months in Florida, maybe the ground would cool back down during the winter when I’m not using it so come the summer it’s ready to turn on again? During the winter I would just us a couple space heaters if need be. I also worry about health issues. Might be better off using ductless ac/heat system in the metal conex home.

These ground source systems are actually more demanding in terms of design than you might think, and I suspect that a lot of installers aren’t really that good. One actually needs to get somebody who knows how to do the calculations (which depend on variables such as site orientation, window design, and so on). I’d be hesitant to go the earth tube route without having a real engineer work on the design.

Insulation, berming, shade- they all are considerations that can affect your system. I’ve always wanted an underground house, myself!

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The issues to consider (probably not all of them, but for starters):

  1. You need to so some serious heat calculations. What the average ground temp is at the start of the cooling season, how much heat you will be putting into the soil and how will that effect the soil temps near the tubes, and how quickly will that heat will dissipate, or be used during your heating cycle. If you are not planning on insulating the soil with the tubing to decouple it from the surrounding environment then the calcs get more complex. You will need to account for natural soil temp as the seasons progress.

  2. With 59" of precip a year, seems like there could potentially be quite a bit of water moving through your soil. That might work for or against your heat moving, but likely needs to be factored in. Also with that much moisture around dealing with water infiltration into the pipes needs to be considered and the potential for molds and other growths in the pipes may be a concern. One also need to address how the water that condenses inside the pipes as the air cools will be eliminated, if you don’t mold will likely result.

  3. What folks who use the SCHS system (an underground soil contact tube heat storage system) in their greenhouses have generally found is: At the beginning of the heating season, the ground is cool enough for the SCHS to do an adequate job of cooling the GH (and storing daytime heat for use at night). But by the middle of the summer, cooling efficiency is way down, as air temps are higher and the soil around the tubes has warmed reducing its ability to absorb more heat. (and the reverse becomes true when you try puling heat out in the fall) Unless you have a way of “getting rid of” that heat you moved it reduces the heat transfer efficiency. That is one of the big advantages to air-air heat pumps and heat pumps which use ground water which can flow away along with the heat it carries. Stored heat transfer system have their uses, especially when you will be using that stored daytime heat at night, but when there is a lot of heat to be pushed into that same thermal mass, it gets less and less efficient the more heat is in there.

  4. Knowing the depth of your water table throughout the year will be important. No matter how carefully the pipes are put in, there WILL be leaks if they are under water. This needs to be planned in to your design.


I’d be very cautious about such a system for a house in FL. The potential for mold seems very high. Unless you can find someone else using that system successfully you stand the chance of damaging both your house and your health. AC lowers both temperature and humidity inside a home in summer. That would be my choice regardless of cost. Spend your money on insulation and AC.

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I second that- wish I could have more insulation in my walls; it just makes everything so much simpler.

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