# Earth tubes, (heating and cooling)



## farminghandyman (Mar 4, 2005)

Earth tubes, (heating and cooling) 

Does any one have any practical experience with earth tubes, 

they are tubes that are buried in the ground below frost line, and air is blow through them in the winter heating to an extent and summer cooling 

much like haw a cellar works, 

what My Idea is to have a system that is vey low on power usage, that could keep a small cabin from freezing up in the winter, and would be basically maintenance free, and in the summer possibly keep the building at a reasonable temp, or help, any way, 

what are the pit falls and what mistakes does one need to watch out for, 
how effective is it?


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## unregistered353870 (Jan 16, 2013)

I don't have practical experience with this, but have studied them a ton. The biggest problem I've seen is mold growth from the condensing water, so you need to slope them to a drain of some sort.


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## SolarGary (Sep 8, 2005)

Hi,
I've collected some experiences from earth tube projects and some design info here: http://www.builditsolar.com/Projects/Cooling/passive_cooling.htm#Other

This is a sort of summary of what's in the links above: 
http://www.builditsolar.com/Projects/Cooling/EarthtubeNotes.htm

Some of the Passive House homes have used earth tubes to preheat the air going into Energy Recovery Ventilation systems that supply fresh air to the house. 

This is another home that uses earth tubes: 
http://pesn.com/2012/06/24/9602115_Tour_of_David-Allans_Solar_Home/
The video describes the installation and how well they work.
Its a pretty interesting house with or without the earth tubes.

Gary


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## 1shotwade (Jul 9, 2013)

Don't know about that but what I have done is use a post hole digger and go as deep as possible with a hole in the ground then Lay blocks around it with a sheet of plastic on top. I used this for a passive heat/cool for my bee hives.Just placed the hive on top as usual.I don't know if it helped or hurt in the winter 'cause they go somewhat dormant but it definitely kept them cooler in the summer.


Wade


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## fishhead (Jul 19, 2006)

No experience with them YET but I thought they would make a great dehumidifier or a person could sink a dry well in the basement and force air down to the bottom to cool and dry the air inside the building.

I worked for a guy who claimed to gotten a patent for an "air well" at a previous job. He claimed that the water it produced was super clean of pollen, mold spores and bacteria.

I have read that in order for the earth tubes to transmit heat they need to be enclosed in moist earth not dry.


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## Jim-mi (May 15, 2002)

And that moist air leads to Mold...............


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## Wolfy-hound (May 5, 2013)

In Florida the water table is really high, so it would make the air more humid, instead of dehumidifying it. I researched the idea(they didn't call it 'earth tubes', no fancy name, just the idea of burying hoses or piping to use as a heating/cooling coil) but I've never had the means to do it. There's so many roots on my place that digging it out would be a ton of work.

Other than the moisture, I don't see why it wouldn't work. You might have to run a dehumidifier inside if it became an issue.


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## Jim-mi (May 15, 2002)

And the dehumidifier would run 24/7 chewing up a lot of electric.
The one I have is a huge pain to try to remember to empty the condensate pan. 

So not at all a 'perfect' solution.

I have read of way too many folks finally admitting to the mold problem.


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## fishhead (Jul 19, 2006)

I don't see why you can's slope the pipe so as to collect the water where you want to prevent water sitting in the pipe. If you were in sand as I am a person could put a hole in the collection spot and let it drain out of the pipe as it collects. That would keep the pipe dry and add needed moisture to the ground around the pipe.

The earth tubes would act as a dehumidifier as long as the temp inside the pipe is below the dew point.


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## farminghandyman (Mar 4, 2005)

on the average were normally at about 10% humidity


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## fishhead (Jul 19, 2006)

In that case you probably don't need the dehumidifier. You may have to figure out a way to keep the ground moist around the tubes to help with heat transfer.


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## bowdonkey (Oct 6, 2007)

I've read of radon problems where soil contains that. Here in MN we are the highest in the nation with radon problems in homes.


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## farminghandyman (Mar 4, 2005)

First of all if one has a sealed pipe, soil moisture and radon would not be an issue on the air quality. as it would be separated from the soil and the radon, 

now I had not heard of the soil moisture helping it work, were dry in general around here, so that could be a area for further study,


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## Harry Chickpea (Dec 19, 2008)

Add an air to air heat exchanger. Moisture and radon issues solved.

The mental trap people fall in is seeing these as completely passive. If the airflow is sufficient, using something like these in conjunction with a heat pump or even as furnace intake air can improve efficiencies.


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## gobug (Dec 10, 2003)

John Hait is a Missoula MT engineer who used 2 very long adjacent tubes (air in & out)under an umbrella of insulation on top of a cement dome buried 6 ft beneath the dirt. He called it PAHS (passive annual heating system). He kept the temperature at about 68degrees F using only a small fan.

Missoula is not dry. So the higher heat conductivity of damp soil could be part of his success. Since most of CO is arid or close to it, wouldn't the length of the tubes be the variable to adjust for adequate heat exchange?

Don Stephens is an architect who has used this technique in several locations around the country. He used a wide border of insulation to go around quasi-conventional style homes (his designs, not subterranean). Mold and mildew are certainly issues of concern. IIRC, he had a sponge in the middle of a string long enough to pull a disinfectant soaked sponge through the air tubes.

Radon is another complication. CO is not the worst, but still a concern. The tubing must form a complete vapor barrier to prevent the radon from getting into the structure. Since radon is a lot heavier than air, the air tubes could provide a path for the radon to leave the structure instead of pooling inside. Regardless of the tubes, the soil beneath the structure needs a vapor barrier. Cement wont work. And a radon reduction vent with the option for a fan is fairly common in CO.


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## mrs whodunit (Feb 3, 2012)

I know of a house that has them. They dont work because the pipes aren't big enough. He didnt have the $ to do larger and thought that size would work. His is supposed to be natural air flow. I dont know if he could do a fan to assist or not.

I think he has about 4 inch pipes.


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## fishhead (Jul 19, 2006)

gobug said:


> John Hait is a Missoula MT engineer who used 2 very long adjacent tubes (air in & out)under an umbrella of insulation on top of a cement dome buried 6 ft beneath the dirt. He called it PAHS (passive annual heating system). He kept the temperature at about 68degrees F using only a small fan.
> 
> Missoula is not dry. So the higher heat conductivity of damp soil could be part of his success. Since most of CO is arid or close to it, wouldn't the length of the tubes be the variable to adjust for adequate heat exchange?
> 
> ...


Do you have any articles on his construction technique?


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## SolarGary (Sep 8, 2005)

fishhead said:


> Do you have any articles on his construction technique?



If you search down this page for "Hait" there is some material on his publications and a book review.
http://www.builditsolar.com/Projects/SolarHomes/plansps.htm

Gary


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## fishhead (Jul 19, 2006)

Thanks Gary.


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