This paper presents experimental results from the small-scale 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 small-scale tests report
wetting of the different wall components under constant and cyclic high temperature loading. It is found that, due to the temperature
gradient, an important vapor flow is generated to the back wall, wetting the oriented-strand board (OSB) sheathing, mineral wool
and gypsum board. The vapor permeance of the interior finishing determines the wetting of the gypsum board: a vapor tight vinyl
wall covering leads to significant wetting of the gypsum board and very low drying rates during drying. A vapor open paint finishing
reduces the moisture content of the gypsum board by a factor of 4 to 6. The magnitude of thermal loading determines the rate
of wetting and drying. Hence, during cyclic loading, where the average thermal loading is lower than a constant high temperature
loading, the wetting potential of the OSB and gypsum board reduces. With the lower thermal loading, the drying of the OSB and
gypsum board is reduced which results in higher final moisture contents. The presence of a wood stud leads to lower moisture
contents of the back wall for vinyl wall covering finishing, since the wood stud absorbs part of 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.
spun-bonded polyolefin (SBPO) and building paper (BP). On
the gypsum board, two different finishings are used: a two-layer
acrylic paint and a vinyl wall covering (VWC).
The indoor and outdoor conditions aim at representing
summer conditions in Charleston, South Carolina, including
solar radiation on the outside cladding and conditioned air at
the indoor side.
This paper presents experimental results from the small-scale tests of the ASHRAE-1235 project on solar-driven vapor transportin wood frame walls. The objective of the tests is to produce precise measurements on wetting and drying behavior of internalparts of the back wall, when a wetted masonry cladding is loaded under cyclic temperature loading. The small-scale tests reportwetting of the different wall components under constant and cyclic high temperature loading. It is found that, due to the temperaturegradient, an important vapor flow is generated to the back wall, wetting the oriented-strand board (OSB) sheathing, mineral wooland gypsum board. The vapor permeance of the interior finishing determines the wetting of the gypsum board: a vapor tight vinylwall covering leads to significant wetting of the gypsum board and very low drying rates during drying. A vapor open paint finishingreduces the moisture content of the gypsum board by a factor of 4 to 6. The magnitude of thermal loading determines the rateof wetting and drying. Hence, during cyclic loading, where the average thermal loading is lower than a constant high temperatureloading, the wetting potential of the OSB and gypsum board reduces. With the lower thermal loading, the drying of the OSB andgypsum board is reduced which results in higher final moisture contents. The presence of a wood stud leads to lower moisturecontents of the back wall for vinyl wall covering finishing, since the wood stud absorbs part of 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.
spun-bonded polyolefin (SBPO) and building paper (BP). On
the gypsum board, two different finishings are used: a two-layer
acrylic paint and a vinyl wall covering (VWC).
The indoor and outdoor conditions aim at representing
summer conditions in Charleston, South Carolina, including
solar radiation on the outside cladding and conditioned air at
the indoor side.
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