EARTH AIR TUNNEL || HOW IT WORKS || passive cooling technique

An Earth Air Tunnel (EAT) is a unique approach to building ventilation that uses the stable temperature of the earth to pre-condition incoming air before it enters a building. This technology can significantly reduce a building's energy consumption and environmental impact by reducing the need for traditional heating and cooling systems.

In an EAT system, a series of underground pipes are buried beneath the building, allowing outdoor air to be drawn through the earth and naturally cooled or warmed to a stable temperature before entering the building's ventilation system. This process also helps filter the air, removing pollutants and allergens, and can even provide humidity control.
earth air tunnel is passive heating and cooling technique using geo thermal energy.
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[alidycepaisley]

For those who are skeptical of the general principle of the system, this is not actually a new design but is a slight variation of a very effective form of passive cooling that has been in use in larger structures in desert climates for centuries or even millennia.

The scale of the system is different. For instance, the underground pipe would normally be more of a tunnel and the inlet would normally be situated atop a high structure such as a tower or turret, not close to the ground. The system outlet would also be situated up high.

Concerns about insect intrusion are valid but I've never understood why you couldn't just cover the inlet with filter material and grating.

Desert climates tend to be more arid but the aforementioned tunnels often have significant quantities of water inside of them that has condensed and settled out of the air and mold doesn't seem to be a problem for some reason.

Interesting concept.

[rronmar]

If you cool the air below the dew point moisture will condense in the pipe. The air is full of various spores which will love the dark, cool and moist environment inside this pipe. In order to move air with the least resistance, the pipe will need to be larger and will need something to cause turbulence for the best heat transfer. You also need a structure that is sealed well enough to develop enough stack effect and enough Vacuum to draw air thru this pipe instead of thru every leak in the envelope. IMO, a far better way to do this is to bury water pipe in the ground and circulate water thru it to chill the water and run it thru a fan-coil/radiator. Any condensation will occur at the radiator where it can be dealt with. You can also circulate room air thru it for increased cooling and better climate control. A little more expensive and complex, but all commonly available components…

[NineInchTyrone]

Great idea to have music louder than the narration ! Genius !

[alexjack]

Hi, here, in France, we call this a 'puit provencal' or ''puit canadien' (puits= well). We use it since...; roman times. Used in persic golf since... long times, I saw the heat system in ancient korea is similar. The tunnel have to have a of 5°(+-) gradient to allow water and vapor to flow out of the tunnel in order to avoid bacteria or fungus. Tunnel, best build in ... 'terra cotta'. No radon, no infiltration, no bad smells. Concrete has radon isssu. Metal will be 'eaten' in less than a year, PVC can break, develop bateria, bad smells. Best to have the fan in the house, in basement for maintenance. Not necessary to dig 4 meter, it can be effective with 2 meter start (remember, gradient is needed). The size have to be calculated between heat exchange effectiveness air air flow ( to avoid issue and to heat/cool the building with efficientcy).
Here, i saw the system connected to 'heatpump'. it used as a pre treatment of the air (air is already cooled a little in summer, and, already warm in winter, so the sytem have to spend less energy to warm/cool the building.

[randallshuck]

My uncle, a civil engineer, set up a system at his home in Kansas that was essentially the same. He put it in in 1948 and it still was working flawlessly at his death in 1999. He kept his house at 65 to 70 degrees Fahrenheit year round without a furnace or air conditioner just a small fan governed by the thermostat.

[gkw]

Thank you that's interesting, managed to hear most of your lines in spite of the too loud music.

[bobsherrill]

I first saw this system in about 1973 in Texas. They used concrete pipe and the constant air flow kept the air dry. I would put gravel under it and a french drain. The one I saw was 150' long and about 15' about 36" in diameter.

[rockyraccoon]

Thank you. There are some posts that mention, what I consider to be important issues, mold, and flooding even radon gas. But interesting idea and nice to see some innovation.

[robertchristianson]

This tech has been used for centuries and works amazingly well. It is a form of geothermal heating and cooling.

[necspenecmetu-]

this principle had been used for centuries in the city of Yazd in Iran and actually uses the wind to move the (hot) air coming from the desert surrounding the city to below the house for cooling and then back up to the rooms now cooled. this system is entirely passive and surprisingly efficient. When I was there the temperature outside was very hot but in the houses it was very fresh and pleasant. I am still surprised that it took so long to adopt it in the western countries.

[jrs]

Rodale's New Shelter Magazine introduced "cooling tubes" for homes back in the early 80's. I remember they spotlighted a home around the Atlanta, GA area. The concern about Legionnaires' disease turned interest away from cooling tubes for passive home cooling. They also had solar chimneys in their design. Great magazine ahead of its time.

[davidchapman]

I saw a similar device in service at Sion National Park in Utah some years back. I am glad to learn how it works and impressed at it's simplicity and efficiency.

[jeffreyyoung]

When I was a kid, a friend lived in an underground house, and it was very cool in the summer, and warm in the winter.
Why we still keep building up, rather than down is beyond me.

[Nikola__K]

The tunnel shouldn’t be very long, just an ordinary waterproof ceramic pipe would do.

Plastic isn’t a good heating conductor so it wouldn’t be good, metal is but it could rust.

The tunnel should have a service port inside the home, where you can service the ventilation fan and filters.
It would be nice if it also had a filter on the other side.

A nice option would also be a drainage system on both openings in the house and outside, so if insects or something else goes into the system to nest you can fill it up with high concentrations of chlorine and water for a day or two to eliminate them, then drain it away. You should also have a valve inside the house to close it so the chlorine doesn’t get in the home when you do it.
This would also come in handy in winter.

[chulee]

Marty from homestead rescue has proved that this type of A/C really does work!
He used a 12v muffin fan to move the air through and lots of PVC pipe.

[DaveE]

You can build a pond/natural pool, raise salmon in it, etc, and install geothermal under that, and the water would keep it a constant temp of deep enough

[mando]

I think I experience this now. I have an enclosed crawlspace and my house stays cool in summer even with little or no AC.

[anthonymonaco]

The earth is not 24C, it is more like 15C at that depth.If you have a well or even city water. Just run you tap water for 5 minutes and measure the temp of the water. That will give the temp of the ground.

[ANJA-mjto]

Clearly approach to reduce cooling! Brilliant cooling example! Great way how to stric temperature control. This is objectivity approach underground with influence of water but with respect to both natural and mechanical cooling is ONE OF THE MOST REFRESHONG AND WORTHWHILE FEATURES that I have seen to be ptojected nowdays. Comprehensive approach 🤩

[williamburroughs]

Looks promising. I would suggest raising the opening to much higher. So the air coming in isn't so hot or dusty to begin with. More heat and particles will be closer to the ground. Heat rises of course but will disperse as it rises.