Ground Heated Air Tubes to Maintain a Base Temperature in Your Home

I think I saw the idea used for a greenhouse (maybe here), but would it work to keep a home above freezing and also keep it cooler?

The idea is to have an exhaust vent with a fan that blows the hot air from the highest, hottest place in your home down through a tube that goes underground to the core temperature, snakes around some, and goes back into the house at floor level.  The fan could operate on a thermostat to kick on if temperature is too high or low.

Is anybody doing this? What would be the downside? I thought perhaps a small solar setup would power the fan and thermostat.

The use of ground tubes aka earthtubes is a form of passive solar.

They are recommended for sustainable non-electric geothermal heating and cooling.

Here is a book you might find interesting:

https://permies.com/wiki/151014/Dan-Chiras-Author-Chinese-Greenhouse

Some threads:

https://permies.com/t/167069/geothermal

https://permies.com/t/120406/Walipini-underground-greenhouse-geothermal-greenhouse

I have seen several good discussions here on the forum so my hope is that some will give you their experiences.

Thank you Anne Miller.

The best reply for me was that the earth tubes are best used in hot, arid climates for cooling. They are problematic in northern climes due to condensation/mold issues mostly. Therre are ways, of course, so if you are determined follow Annes links and learn more. Since I am in the north I will let it go.

Therre are ways, of course, so if you are determined follow Annes links and learn more. Since I am in the north I will let it go.

Hi Tom,
I will say that the post I looked at from Anne Miller brought me right to another post that describes exactly what you were describing. Having a long run of tubing in the ground that has a fan blowing through it to heat or cool the air. I would not be too quick to simply let it go. The wording could easily be misunderstood as ungrateful to Anne's time to reply and post those links.

Now, specific to your question, yes, those sorts of tubes do work, and yes they can have all sorts of problems with mold. I live in the north as well, and generally it is not a problem to keep the air cooler. We want the heat. If money is no object, then running water pipe underground and connecting it to a geothermal heat pump is an excellent way to get hot or cold. It is super efficient but also really expensive.

If you are only interested in heat and want something less expensive, you can look into wall panels. I forget the term, but you put a large panel on the outside of the house. It is maybe 4-6 inches thick with a serpentine path through it. All painted black, with glass or plastic on the outside. There is a a hole at the top and bottom that goes through the wall into the house. With a small fan, you can pull the air in at the bottom where it is the coldest, then back and forth through the path as it gets higher, it gets warmed by the sun, and finally exits through the top vent adding warm air to the room.

Lastly, (also not cheap), is insulation. I know of one house up here in New England that was super insulated. The guy lost power for like a week during sub zero temps. No added heat, his house was still above 50F at the end of the week. In a normal house, the pipes would have been frozen. So while ground heated air tubes are nice, you can also help maintain your base house temperature by insulating it very well so you don't need as much heat to keep it at temp. It costs a lot up front, but you have no ongoing costs, and heating and cooling costs are decimated.

Tom, where are you such that you have heat and freezing conditions?
What sort of temps are we looking at, because that will alter the range of ideas?
Is humidity an issue at any time?
Earth tubes work well without fans and using natural draft techniques.
Wind towers, which I have mentioned on the site may work for you if you want a current of air through the building.

It's an approach that is potentially valuable. I think John C is asking important questions. It's pretty much essential to know your typical environmental conditions, in the hottest and coldest seasons, to give any meaningful feedback. The physics are what they are, and that means sweating out the details. It would be sad to see effort invested and wasted. My 2 cents'.

If I had any say in how questions get asked on the site I would suggest that any energy related question should start out with "where are you".

I have seen that system being used in Canada and upstate New York, so don't dismiss it too easily.

There are lots of passive solar things that are easier in dry climates.  Earthships for example do not work in the neast WITHOUT MODIFICATION for the humidity.  

Tom Bergman wrote:
The best reply for me was that the earth tubes are best used in hot, arid climates for cooling. They are problematic in northern climes due to condensation/mold issues mostly. ...Since I am in the north I will let it go.

I'm hesitant to post because you seem willing to let it go pretty quickly, but I'll give it a shot.

The guy that wrote "Citrus in the Snow" is using earth tubes for heating his Nebraska greenhouse enough to, well, grow citrus in the snow.  He also used them to heat his house, in conjunction with a heat pump.  He basically created a room that he heats to 50 F (if memory serves) with earth tubes, and then uses a heat pump to heat the air from 50 to 70 or whatever.  He addresses the (non)-problem of condensation/mold, but summary his, he doesn't have that issue.  I think earth tubes have a place for heating and cooling in northern climes, and my greenhouse here in WI will utilize them.

As others have mentioned, where you are is a criteria for answering these type question, and, as you might imagine, "fudgesucker" is less helpful than one might first think.

So long as you include a fish tape inside each tube, so you can attach another tape and say a towel soaked in something to clean the tubes, then once or twice a year you pull the towel through to clean out anything trying to grow in there. You can also start with a good furnace filter covering the intakes to limit what gets pulled in too. I don't have my notes in front of me, but there's a certain schedule sewer drain pipe that has pretty thin walls (which improves heat transfer) that is recommended, and of course if you include a gentle slope to one end the condensation can work its way out.

Humid climates certainly are an issue, many people get clogged AC drain lines when they don't proactively clean them, but those tend to be 1-2" diameter. But if you're going to draw air in to breathe, mold and radon gas should be planned around.

I haven't given up on it completely. I have some of this tubing that could be used. I don't intend to do any excavating soon so it will be some time before I could implement anything.
Anne's thread contained many links, with links. I read through quite a bit of it, and I thanked Anne first off.
Off to fix my profile.