Laboratory demonstration of solar driven inward vapour diffusion in a wall assembly

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Conference11th Canadian Building Science and Technology Conference: 22 March 2007, Banff, Alberta
Pages18; # of pages: 8
AbstractOn-going discussions on various forms of moisture transport in buildings have often focused on the nature of vapour diffusion in wall assemblies. Recent field investigations at the Institute for Research in Construction (IRC), NRC Canada, have yielded data on the effect of solar radiation on the exterior surface temperature of wall assemblies. On a sunny day in August 2004, on the exterior surface of a south-facing wall, a temperature rise close to 25°C over the surrounding air temperature was recorded. Coincident increases in the absolute humidity ratio of the air in the cavity behind the brick were measured, suggesting inward drive of brick moisture into that cavity. A laboratory facility at IRC, called the Envelope Environmental Exposure Facility (EEEF) has been used to launch an investigation on the behaviour of the vapour diffusion in exterior walls exposed to solar radiation. A 2.4 m by 2.4 m test specimen of a simple wallassembly was constructed, the exterior surface of the specimen soaked in simulated rain conditions and subsequently heated by infrared heaters to mimic the rise in surface temperature due to solar radiation. The wall was fully instrumented for temperature and relative humidity measurements at both surfaces as well as at every interface. This paper presents a brief description of the EEEF, details of the test specimen and data collection, and data from the above experiment. A clear indication of an inward diffusion of water vapour across the wall as the exterior surface is heated is derived from both laboratory controlled and field experiments
Publication date
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedYes
NRC number49203
NPARC number20377536
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Record identifier72679b7e-dbf1-4734-9b80-137312c3f5e5
Record created2012-07-24
Record modified2016-05-09
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