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Are Tire Bales Insulation or Mass? — 3 Comments

  1. Thanks for this discussion! It really helps my thinking, and makes sense.

    I’ll just correct one common misconception — tire bales have nothing to do with straw. They are just tires, wrapped up with very thick baling wire, to make a compressed block of whole tires (with the inevitable big air gaps since tires have enough integrity that you can’t get all the air out when compressing them). The photo Kelly posted above shows stacked tire bales (at our local landfill).

    It took many conversations over weeks to get our architect and engineers to understand that we didn’t mean straw bales, and didn’t mean that we were using “tire bales” as infill for stick-built walls! They are baled-tire building blocks.

    Thanks again for sharing your expertise, Paul and Kelly! Very helpful.

  2. Hi.
    With regard the thermal mass question vs insulative value.
    Thermal mass, is prominent in adobe, superadobe, masonry etc, a solid material, that allows the transfer of temperature through the material. These walls often have the capacity to hold a thermal charge, ie being heated by the sun. The logic being that the outside air temperature must drop below the wall temp before the wall is able to release the warmer air. There is simple logic to this, physics. The insulative value of a wall, or material, is it’s capacity to resist the transfer of temperature/air, etc. It is not an ambient system, in terms of construction, it requires that there be additional sources of heat, as it isolates the interior from the exterior, with less/resisted transfer of cold. Temperature/heat/cold, require mass to travel, if we use wool, or hemp, etc, the resistance to the transfer of temperature is great, because there is not a lot to transfer that heat/cold through, and hence why cavity wall (masonry) construction was used, and still used in lot’s of Europe, as they need to create a gap so the cold doesn’t travel right across onto the interior face of the wall.
    You’re correct in assuming that with straw filled tires, that the only thermal mass would be found in the plaster and the tires themselves, the straw wouldn’t help much at all, unless compressed with earth, to form a more structured material. Earthships are thermal mass, as the tires are filled with earth, yet still earth isn’t always the best thermal mass store, sand has less thermal capacity than clay, for instance.
    Hope this helps a little.
    Paul
    http://www.havenearth.org

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