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Old 09-09-15, 08:15 PM   #1
MEMPHIS91
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Default Earth Air Heat Exchanger

Pretty sure this is the right place for this thread since it is Geothermal.
I have been studying for a while on how to keep things cooler/warmer in the house without any AC.
This project is NOT meant to make it feel so though the AC is on and working great. This systems goal is to only make it feel better with no AC. Though after doing a lot of research I believe that a somewhat reasonable temp/humidity can be achieved.
The basic concept is to bury a length of pipe 5-7 feet deep in the ground, one end is connected into the house, the other end is open to the outside.
The type of pipe, length, lay out, size, depth, drainage, and many many other variables is what mean success or failure.
I have a 2 story house on a large hill. My plan is to have 1 or 2 pipes per room of the house on ground level, then have a slow moving, solar powered fan venting the hottest air out of the tallest point of the house.
I will be posting pictures of the house, and diagrams of the idea I have soon. Here are some links to some sites I have gotten good info from.

http://libraryfiles.tripod.com/00.pdf

(641) 472-4953 Natural Air Conditioning and Heating using the Earth!

Earth tube heat exchangers

https://www.google.com/url?sa=t&rct=...73utKCjM9bhJwg

There are many more but google quickly pulls up a lot of info.

Plan as of right now is to use this stuff
Shop ADS 6-in x 100-ft Corrugated Solid Pipe at Lowes.com

And cut a very small hole/slot into the bottom of each corrugated rib of the pipe. I will dig 5 feet deep at the edge of the house and end up at 7-8 feet deep where the pipe comes out of the side of the hill. The pipe will be laid with the slots on the bottom to allow any condensation to drain out. The pipe will have a curve in it every few feet as well. I will put 3 inch of gravel under the pipe and fill in around the pipe and on top with at least 2 inch of gravel. Then lay down a filter fabric to keep the dirt out of the gravel. Then I will feel the ditch up to about 2 feet from the surface and lay down some rigid foam in the ditch, and finally cover it all back up. There will be a wooden filter box on the open end of the pipe.
My idea to use the corrugated pipe was to keep the air tabulate, this is also the reason for the curve every few feet, thus "washing" the air over as much surface area as possible.

My only concern is condensation. I have a kinda high water table but I think with the 3 inches of gravel in the bottom under the pipe and slopped to the open ended hill side, drainage should not be a problem.

I will install one of these this fall in order to use it as a pre-warmer for the air that fireplace sucks up the chimney. And real testing will begin next summer. If all goes to plan I will be putting at least 8 more of these in the house.

Ideas? Concerns?

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Old 09-09-15, 09:04 PM   #2
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Earth tubes were REALLY big in the late 1970's as a free way to heat (and cool) homes. Mother Earth News touted this highly.

Fast forward ten years. Mold was (and is) the killer on this idea. In the tubes, you have moisture, warmth and dark - the three essential ingredients for mold growth.

I watched as several clients put these in and then closed them off after having allergy issues - some severe.

There are still those that claim and assert that there is no mold. I am sorry to be such a skeptic, but I am unaware of putting in a liner (on the tube inner surface) that eliminates this. And it cannot just be minimized - it needs to be eliminated.

The physical problem is that earth temperature is ALWAYS going to be below the dew point of the air at some time in the year. Volia - condensation.

The other issue is that the air comes into the home at ~ 100% relative humidity. Yes, it is cool air, but it is damp, cool air. And without a very dry air mass (such as in Arizona where "swamp coolers" work well, with a relative humidity in single digits) you just get nasty damp air.

Yes, you can put in slots in the tubes, you can put in drainage "canals" at the base, but you can't overcome physics.

I love the idea for makeup air for fireplaces and for inlets to wood stoves. But for house air, I would say not.

Great idea, but it failed miserably when tested considering the health issues. It works GREAT as a cooler with 100% humidity introduction into the home. And in winter, it GREATLY prewarms incoming tube air and bring in all the mold spores as the surface mold dies (cold air kills mold) and the former mold growing biology in the tubes now releases billions of billions of mold spores.

Uggh . . . .

Sorry to be a wet, cold and damp blanket . . . . but you gotta know the history.


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Old 09-09-15, 09:59 PM   #3
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Steve,
Mold/condensation is my number one concern. But I believe that the cases of the mold that really caused bad problems were badly installed systems. (http://www.greenbuildingadvisor.com/...rth-tube-story) The good news is that I have access to a high pressure jet machine used in the plumbing world. So if/when some mold forms I can completely clean the pipe out, and do this on a routine, kinda like cleaning your shower.
Also I am not using the PVC solid pipe. I think a lot of systems used PVC and I believe it is impossible to get every drop of water to drain out of a long piece of PVC. With corrugated pipe each and every inch will have its own drain.
Pull no punches, I will do nothing that will endanger my family. I will take every warning seriously and as always TEST TEST TEST before I go full scale.

Awesome article: https://milligansganderhillfarm.word...ool-your-home/
I also have a pipe line inspection camera, so when the test do start I can get a good picture of the pipe if it starts to form mold.
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Old 09-10-15, 06:48 AM   #4
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Memphis,

I have read that article and it again sounds encouraging. But I have read many of these "no mold earth tube" techniques over the years.

When corrugated tubes are used, you can get substantial mold now growing in the dirt that is drained at each point in the tube. Mold also needs air - and together with moisture, warmth and dark you still have the "recipe" for mold.

Build a small tube and use it for your fireplace/wood stove make up air. Easy to test for mold spores in that trial aspect.

We are recognizing that mold can be a very dangerous situation with it causing many other issues - some quite dangerous. Older homes had some mold, but they were also so loose and drafty that it was not a substantial issue. But couple a tight house with low air changes per hour (ACH) and then a mold introduction section, then you have danger.

Mold is not something that you take away and the medical problems disappear. Mold seems to trigger a whole pathway, that once initiated, continues to cause a lot of medical problems. Allergists find this very frustrating.

Recall underground homes from the 1970's? Another great idea that minimized the heating cooling delta t, minimized air infiltration, etc? The idea was to cover the outside of the concrete structure with foam panels to prevent critical dew point condensation on the interior walls. But ANY tiny gap in that exterior insulation and condensation (and mold) occurred.

Interior condensation remains a big problem and many of these homes had to be complete covered now on the inside with insulation panels to prevent dew point condensation (and mold). But that just kept the mold behind the panels where it was now dark, humid and wet. Eventually mold spores get out and again cause home air quality issues.

I do a lot of work for the American Lung Association (allergy and construction issues) and we are coming to the conclusion that mold is far more of a home problem than we ever imagined. Tight homes, when ventilated properly with ERVs, still can have critical mold issues. The key is to prevent mold and not just to wash it away with more air changes.

Underground construction is now waning as above ground envelope techniques and better insulation and installation techniques nullify the low delta T aspect.

You have seen the power of the geocoupled heat pump. I would use that technology first, but give the fireplace tube a try.


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Old 09-10-15, 07:57 AM   #5
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Steve, that is something I had not thought of, mold in the dirt around the pipe. That is a very good point, and maybe what makes me use PVC instead. I could use the money I saved not putting gravel in to buy some thin wall 6" PVC. This would also make it MUCH easier to clean and I could add some bleach into the Jet machine. Though I'm guessing I'll need to go longer than 100 feet now.

Mold is terrible and in the south we have lots of it. Good to know that people are getting serious about how bad it is for everyone.

There are a few underground homes here in Lafayette County. I have pumped their septic tanks. Must be a newer way of building because they said they had no mold issues and the houses have been there for over 20 years.
Speaking of septic tanks that gave me an idea. With Advanced treatment unit, a 80 Liter per minute air pump is pump air under the water in the septic system 24/7/365. Then is vented out of the vents on the house or out the discharge line. I have never seen any mold. Warm, wet, and dark. I wonder if the septic waste has a low enough PH to kill it? Just a thought.

Not that it will fix the problem at all, but the house will have many air changes when the tubes are used for cooling and thus more chances for mold.
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Old 09-10-15, 08:01 AM   #6
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Memphis

I have some first hand knowledge of the earth tube. As Stevehill has described mold and related issues.

On this particular installment albeit not with all the drain holes (that may get clogged with mold) the first season was awesome. The following years there was a foul stench emanating from the tube. The question. How can I repair this??? It was capped off.

I would caution against this installation. A humid warm climate would promote mold growth. Even with our -22 Deg. C. winter the air did warm on its way to the house and mold was not killed-off in those last few feet.

Don't mean to rain on your parade.


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Old 09-10-15, 08:37 AM   #7
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Do you have more details on your installation?
I'm a stubborn man when I know that it has and is working on a number of houses. If mold build up in a year then twice a year cleaning should be fine.
Haha no parade to rain on here, I'm diving fence post this morning.

I am interested in all the success and failure stories.
Thanks for your guys input.
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Old 09-10-15, 07:05 PM   #8
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Just an idea. Would placing a few of these type lights inside the pipe help the mold problem? If I got white pvc that would reflect nicely.
Air Purifier UV Light for AC HVAC Ultravaiolet Dual Lamp Duct Air Cleaner Deal | eBay
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Old 09-10-15, 07:15 PM   #9
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Memphis,

Yes, high intensity UV light does kill mold spores, viruses, bacteria, fungi, etc. But only when they are at low concentrations and when the system recirculates the air over and over again (as in a conventional HVAC system).

Sadly, PVC is well known to grow vigorous colonies of mold and mildew. I have a very nice, formally white PVC fence that grows mold quickly - and it is not even in the dark!


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Old 09-10-15, 07:28 PM   #10
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Good point, maybe then that is why a lot of systems have failed, the material , that being PVC in most cases, is a terrible choice.
I will look into pipe that is less prone to mold.

Maybe http://www.homedepot.com/p/Advanced-...0010/100135310

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