It was shown that, for the constant and cyclic loadings of
the test, the type of weather resistive barrier does not change
substantially the wetting and drying behavior of the OSB and
gypsum board.
The presence of a wood stud leads to lower moisture
content of the back wall for vinyl wall covering finishing,
since the wood stud absorbs partly possible flow to the gypsum
board. In the case of vapor open finishing, the hygroscopic
behavior of the wood stud leads to higher moisture contents of
the back wall.
In the (severe) tests with constant boundary conditions,
the moisture content of OSB and gypsum board are too high
in all cases producing moisture related problems. In the cyclic
loading with vapor open paint, which is the less severe case,
the maximum moisture content for gypsum board is still 13 kg/
m3
and for OSB 80 kg/m3
which respectively equals to relative
humidity of 86% and 90%. In both cases, ventilation of the air
space was not included to better understand the role and
impact of the interior finish material.
While the tests and analyses are ongoing, we hope that we
have at least met some expectations of the reader, whereby we
point out the existence of solar driven vaportransport and the
possibility of severe moisture damage when a vapor tight
finishing of the gypsum board is applied. We showed that,
even with vapor open interior finishing and more moderate
thermal loading, problems may arise and wall compositions
have to be optimized. In further progress of the project, the
experimental results, including the presented small-scale tests
and the on-going large-scale tests and field measurements,
will be simulated and the simulation models will be validated
and used for further analysis under different yearly climatic
loading.
ACKNOWLEDGMENTS