“To start with the most often voiced concern; that the bale will deflect when used as a structural element, much like any other piece of rubber. This is true, they will deflect, and the tests have proven it so. However, they have been “deflected” considerably to become “bales” in the first place, and the load required to deflect them further than is acceptable (more than your house will ever weigh), is roughly 1/20 of what has been called a “failure” (150,000# on an unsupported bale; usually when a wire breaks). In other words, your house will NEVER exert that much load on a tire bale wall used as a foundation wall. Also, a steel reinforced concrete bond beam is poured in-place on top of the tire bale wall, to distribute load of the roof framing and possible loads placed on the roof.”

“The Colorado School of Mines study that we have discussed predicts that the thermal conductivity (U) of tire bales can range from:

0.120 – 0.124 Btu / hr ºF ft

Which converts to an R-value range of 0.694 – 0.672 per inch, or a total R-value of 40.0 – 41.6 for a 60″ tire bale wall. This is a far cry from the undocumented claims of R-120 for the same thickness, but it would nevertheless equate to approximately 11.75 inches of fiberglass batt insulation – about what you could put into a 12″ thick stud wall… which is about 3x as much insulation as goes into a standard 4″ stud wall…very good wall insulation by conventional standards. This material should yield super-insulation-like performance if the entire wall is assembled and completed properly from interior to exterior…

Moreover, the tire bales also have a predicted Specific Heat (Heat Capacity) of 0.18 Btu / lb ºF. This compares favorably with other common thermal mass materials like sand (0.20), stone (0.20), and concrete (0.15). So, the heat storage capacity of the tire bales in a passive solar house should be excellent as well. For the house Mikey mentioned in a recent e-mail, the tire bales alone – at a 10ºF temperature drop should have a storage capacity of:

130 bales * 1T/bale * 2000 lbs/T * 10 degF * 0.18 = 468,000 Btu

Nearly half a million BTUs is a considerable amount of heat! The interior plaster will add even more heat storage… So – perhaps it is possible to have one’s (thermal) cake and eat it, too…!! The tire bales should provide excellent insulation – and – provide good heat storage as well. The price one must pay for this, of course, is the massive thickness and weight of the tire bale wall.” … Thanks, Leonard.
the resultant house

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