Here are some external “earth tube” links…
A Google search for “Earth Tubes” or “Cool Tubes” or “Air Earth Heat Exchangers” or “Ground to Air Heat Exchangers” or a variety of other terms can turn up many more
This is what Wikipedia has to say about it. One of these days, I should improve their content…
Using earth tubes (which he calls GeoAir Energy), Russel Finch heats his home and green house (he also grows and sells citrus).
Oranges in Nebraska; “Every time an expert tells me it can’t be done, I sit back, peel one of my oranges, and marvel at my ability to eat something that is impossible to grow in Nebraska.” ~ Russel Finch (A very similar article) (Citrus in the Snow website)
See the link for more images and details of this Earth Tube installation.
This is an “Earth tube Exhibit” done by the Clean Energy Exhibition. They talk about a study done on the tubes, but i have not been able to get any data. Still nice to see the pics of the install. In this case, they “saved money” by stacking many pipes in a single trench. Personally, I think this dramatically reduces the effect of the tubes, which is sad considering that digging the trench is probably the lowest cost portion of the project.
REHAU manufactures a system of pipes specifically designed as Earth Tubes (Ground Air Heat Exchangers). These include filters and other specialty sections.
Rehau is known as one of the few commercial Earth tube providers (they call them Ground Air Heat Exchangers and use the brand name “Ecoair”). This is a link to a story about one of their homes.