I was reading an old issue of Countryside (69/2 published in 1985) and was fascinated by an article on heating outbuildings by burying half a dozen PVC pipes twelve feet underground in a radiant pattern from the end of a building. The ends of the pipe closest to the building then come into some kind of fan/ventilator to draw air through the pipes. The outer ends of the pipes have a 90 degree elbow in them at their end and another pipe connected so it comes straight up out of the ground and then has a little roof on it to keep the rain and animals out. The principle is that the ground temperature remains quite stable at twelve feet so when you are having cold weather or hot weather outside, the temperature at twelve feet below is much different. By pulling outside air through these tubes, it cools or heats the air and then the air is conducted into the building. It really looks like a quite simple and inexpensive system except for figuring out how to get the pipes buried twelve feet under. The article said that it could only meet about 60% of your heating and cooling needs but it sure seemed like a winner to me. I was just curious if anyone uses a similar system to heat/cool their outbuildings or home. I would love to hear more about it and how they installed it since the article was not very long and did not give a lot of particulars about it because it referred you to somewhere else for more info.

-- Colleen (pyramidgreatdanes@erols.com), August 08, 2001

Answers

Did it mention the lengths of these buried PVC pipes? I really don't know much about geo-thermal heating/cooling... but I'd hazard a guess that the system would be huge.

cheers,

-- Max (Maxel@inwindsor.com), August 08, 2001.

Colleen, I was reading about something similar a few years back and getting all excited about it. However, more digging around informed me that mold/mildew would/could grow in the tubes, and then you're blowing that into your house! So I gave up pursuing it. As I said, it was years back, so I have no sources to give you.

-- Joy F [in So. Wisconsin] (CatFlunky@excite.com), August 08, 2001.

I've heard the same thing about mold/mildew. Also, who would want fifty degree air blowing into their home int the winter? That would feel pretty awful, unless your house were normally forty degrees.

I have had the idea to do pretty much what you suggest, but blow the air over the outdoor unit on a heat pump, to raise the heat pumps efficiency. The fifty degree air would be warmer than the ambient air in winter, and colder than the air in summer. Plus, the heat pump wouldn't get bronchitis from mold.

JOJ

-- jumpoff joe (jumpoff@ecoweb.net), August 08, 2001.

I wonder if a HEPA filter wouldn't take care of any mold problems? Or periodically running a cleaning rag through on a line?

-- Laura Jensen (lauraj@seedlaw.com), August 08, 2001.

Yup Colleen, I have one. Consists of 6 200' lengths of 4" drain tile wrapped around the footings of my house, about 8' below grade. Inlet and outlet inside the basement. Inlet (soon to be) filtered, outlet in the air handler. Squirrel cage blower sucks air thru the tubes. Air is cooled and blown thru the ductwork. Important to put 4-6" of dirt around each tube as a heat sink. Also important to provide drainage in the tubes to eliminate the condensate that would otherwise build up. I did this by setting a circle saw blade so it would cut about 1/16" deep and cut slots on the raised portion of the drain tile. I'm happy with it and it definitely help to keep the house cooler. I've run it three yrs now and no evidence of mold.

-- john (natlivent@pcpros.net), August 08, 2001.

I just read an article on it in a recent issue of Countryside or Mother Earth News. There also have been articles in Popular Science about a man who figured out a simple system that would work for any home, even in a subdivision where space is limited. He plans to market it to Apartments and Condos. I'll see if I can find the details and post it here.

Chris

-- Chris Tomlinson (cdtomlinson@hotmail.com), August 09, 2001.

JOJ- I think the idea behind having 50 degree air coming into your house in the winter is that it costs less to heat 50 degree air to 70 degrees than it is to heat 10 degree air that would be seeping in anyway. That's the rational I've always read for these systems anyway.

-- debra in ks (windfish@toto.net), August 09, 2001.

Debra, I've heard that case made, but think about it. Would you open all your windows if it were fifty degrees outside, to let in the "warm air"? I don't think so.

JOJ

-- jumpoff joe (jumpoff@ecoweb.net), August 10, 2001.

I found it. The May Mother Earth News discusses Geothermal, but the best article was in March Popular Science. John Genung is a retired TVA engineer and he started a company called Energy Recycling Group to build the Geo Column. Short article, but worth reading/researching.

Chris

-- Chris Tomlinson (cdtomlinson@hotmail.com), August 11, 2001.

John, I'm a long time lurker and have only posted a few times but I have a possible concern about your set up. Radon gas is a problem in some ares of the country. I would be worried about your system drawing it into your home, especially with the slots cut into the pipes, and with drawing air through the system instead of pushing it. Maybe you have already accounted for this, but if not I would have the air tested. I believe there are kits available to do this.

-- Bruman (bruman@bright.net), August 12, 2001.