CONCLUSION
This paper presents experimental results from the smallscale
tests of the ASHRAE-1235 project on solar-driven vapor
transport in wood frame walls. The objective of the tests is to
produce precise measurements on wetting and drying behavior
of internal parts of the back wall, when a wetted masonry
cladding is loaded under cyclic temperature loading. The walls
are constructed according to typical North American
construction practices, with vapor open mineral wool as insulation
material between the studs. In the presented small-scale
tests, eight horizontally placed specimens with different
weather resistive barrier (SBPO and building paper), interior
finishing (vapor tight vinyl wall covering and vapor open
paint), with and without wood stud are exposed to a constant
or cyclic varying outside thermal loading. The inside loading
is constant and at lower temperature.
The small-scale tests show that, due to the temperature
gradient, an important vapor flow is generated to the back
wall, wetting the OSB, mineral wool and gypsum board.
Moisture uptake by the gypsum board covered with the vaportight
vinyl wall covering is much higher than the uptake of
moisture by the gypsum board with vapor open paint. Vapor
open paint finishing reduces the moisture content of the
gypsum board up to a factor of 4 to 6.
The magnitude of thermal loading determines the rate of
wetting and drying: during cyclic loading, showing on average
a lower thermal loading, the wetting of the OSB and gypsum
board reduces. Also, as a result of the lower thermal loading,
the drying of the OSB and gypsum board reduces resulting in
higher final moisture contents.