Moisture convection performance on the joint of external wall and attic floor - laboratory tests and two-dimensional simulation model validation

Full-scale laboratory measurements were conducted to determine moisture convectionperformance on the joint of external wall and attic floor. According to field measurements inprevious studies this joint is one of the most typical air leakage paths. On this joint also thehighest air pressure difference forms in winter. Two commonly used external walls: timberframeand autoclaved aerated concrete walls were measured. The attic floor was in both casesa timber-frame structure. Results from the first laboratory measurement series showed that inleaky joint the moisture convection due to positive air pressure remarkable raised moistureaccumulation rate on the inner surface of sheathing. A two-dimensional heat, air, andmoisture transport computer model was validated for future analysis. The simulation resultsshowed that CHAMPS-BES program is useful tool in assessing the moisture behaviour ofbuilding components including moisture convection.