Herbert,I appreciate that you support the high (low) numbers achieved in the tests you mention. I also agree that the MacCabe tests are not indicative of normally attainable Lambda values. But I have serious reason to doubt that actual SB buildings will achieve the 0.045 you and the tests mention. Nearly all other tests (not only the Mac Cabe test which again I think is an anomaly Check Bruce Kings website for an overview of the tests) show much lower values. I cannot accept that the relatively coarse, open, patchy SB can almost approach the same Lambda value as specifically fabricated insulation materials exhibiting much better capability to entrap air in small pockets.
I am sure the tests have not been tricked or rigged to achieve the high values. I just think values measured are due to the very specific circumstances under which these tests are executed. ie the test does not properly reproduce circumstances that arise under real building applications. I am not saying the tests have been faked, just they don't allow for the specific characteristics of natural building materials exhibiting greater variance and in-homogeneity. We are interested in how the system works as a whole and not what the specific performance is of one single component. Most conventional materials perform quite poorly in this respect then a SB wall system. Which is much more homogenous as a whole then nearly all other insulating wall systems. I would love to execute a few field tests using a heat conductance meter to verify values (to maybe even find that the 0.045 is almost true)
In the meantime though I would not count on 0.045 as this could lead to a serious disappointment regarding the performance of the passive house.
A major issue leading to a lower performance of SB as an insulator is the existence of air circulation in the bales this is bigger then in most conventional insulation materials. Higher density bales like jumbos seem to exhibit a better performance in this respect then normal density(115kg/m^3) bales.
On Mar 8, 2005, at 16:49, strawbale-request@amper....muni.cz wrote:
What is quite realistic? I wonder that you cannot accept, that the OFFICIAL heat measurement-tests in Austria and Germany faced much better results thanthe improvised tests of MCCabe in USA. Be sure, there were no tricks: lambda10tr = 0,038, lambdaZ = 0,045(lambda10tr is the value measured on the dry (tr) material at 10 degreesmiddle-temp., lambdaZ is the measured value + 20% addition)
Rene