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We are currently planning on building a 1500 square foot house out of Rastra or Cempo ICF’s. In the July 2000 issue of Fine Homebuilding there was a sidebar written by Scott Gibson that stated that some Oak Ridge Lab found a 10″ Rastra wall to have a static R-value of only 7.6 not the 11 that Rastra claims. The dynamic R-values were higher. My question is what is the difference between dynamic and static R-values? I understand that manufacturers tend to bump numbers a little but this is way out of line. Has anyone else heard of these numbers being so greatly exaggerated and where would one go to find real world numbers? The author stated that these R-values of the Rastra wall put it at less than a 2×4 stud wall with fiber glass batt insulation.
Thanks in advance,
Craig Spaeth
Spaeth Design Works
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We are currently planning on building a 1500 square foot house out of Rastra or Cempo ICF's. In the July 2000 issue of Fine Homebuilding there was a sidebar written by Scott Gibson that stated that some Oak Ridge Lab found a 10" Rastra wall to have a static R-value of only 7.6 not the 11 that Rastra claims. The dynamic R-values were higher. My question is what is the difference between dynamic and static R-values? I understand that manufacturers tend to bump numbers a little but this is way out of line. Has anyone else heard of these numbers being so greatly exaggerated and where would one go to find real world numbers? The author stated that these R-values of the Rastra wall put it at less than a 2x4 stud wall with fiber glass batt insulation.
Thanks in advance,
Craig Spaeth
Spaeth Design Works