Research on earth tubes

Discussion in 'Put Your Questions to the Experts!' started by Honey Run Sandy, Dec 31, 2015.

  1. Honey Run Sandy

    Honey Run Sandy New Member

    Joined:
    Dec 22, 2015
    Messages:
    3
    Likes Received:
    0
    Trophy Points:
    1
    Climate:
    Mediterranian
    I live in a Mediterranean climate and want to retrofit my conventional ranch style home with earth tubes for summer cooling. I have been searching all over the internet to find out what tubes and back fill are most effective for heat transference. It seems like some university must have done research on this but I haven't found it yet. Many people say to cover the tubes with sand, others say gravel. Some say perforated pipe, some say solid. Some say you have to be able to clean them out regularly, others say not. Is there some research based information?

    Thanks
    Sandy
     
  2. 9anda1f

    9anda1f Administrator Staff Member

    Joined:
    Jul 10, 2006
    Messages:
    3,046
    Likes Received:
    199
    Trophy Points:
    63
    Gender:
    Male
    Location:
    E Washington, USA
    Climate:
    Semi-Arid Shrub Steppe (BsK)
    Everything I've read on earthtubes emphasize condensation within the tubes and making provisions for drainage plus the possibility of mold forming.
    As I live in a dry (semi-arid) climate this is not such a concern, but I did install cordage to allow me to pull "witness cloths" through the tubes from time to time that hopefully will let me see how much moisture/dust/mold forms. The tubes I installed are sloped downwards to the far (remote) end and have drainage holes should that much condensation form (say during a rain event in summer).

    Almost all plastics are insulators and as such aren't the best solution for heat transfer. Using copper or aluminum pipes (excellent conductors) would be best for heat transfer and might even allow shorter buried pipe runs but for me the cost would be prohibitive!

    My install is an experiment with 40'+ pipe runs fairly close together. The goal is to temper the outside air temperatures for input to the earth-sheltered greenhouse both during summer (100*F+) and winter (it's 6*F right now and can get to -20*F). I have hypothesized that my earth tubes may be too close together. For instance, as heat is drawn out of the air into the soil surrounding the tubes in summer, that earth will heat up and may, at some point, be warm enough to minimize any cooling effect. More widely spaced tubes would provide much greater earth volume around each tube to absorb this heat.

    Here's some more thoughts on earth tubes: https://www.permies.com/t/19764/earthship/Cooling-Tubes (you may have already seen this)
     
    permiewannabe likes this.
  3. Topher

    Topher Junior Member

    Joined:
    Feb 19, 2015
    Messages:
    25
    Likes Received:
    2
    Trophy Points:
    3
    Occupation:
    Energy & Permaculture Consultant
    Location:
    Midcoast Maine
    Home Page:
    Climate:
    Cold Temperate
    Although plastic isn't a great conductor of heat, for earth tubes it really isn't that big a deal. For one thing earth isn't a great conductor of heat either, (which is why earth tubes work at all). Also air is not a great transporter of heat, so you are going to need a long tube anyways.

    While it might be true that you don't need to make provisions for cleaning out the tube, or draining out the water, I would hate to be wrong about that.

    Thank you kindly.
     

Share This Page

-->