Hygro-thermal performance of wooden beam ends: experimental investigations of uninsulated and internally insulated brick wall

Wooden floors were traditionally used in brick apartment houses built at the turn of 20th century in many European cities. Thermal renovation of such houses often involves thermal insulation at interior side of external walls. Internal insulation makes microclimate in the vicinity of wooden beam ends colder and more humid. The real-scale experiment involving a part of wooden floor connected to a 30 cm thick masonry wall was monitored for two consecutive years. Measured data were used to compare microclimate in sealed and open joist pockets. Joist pockets were either placed in the masonry wall with plaster on both sides or placed in the same masonry wall insulated on the interior side (vapour open thermal insulation system). The measured results indicate that the sealing tape alone is not sufficient to keep the relative humidity in joist pockets below 85 % in cold climate and under high internal moisture load. The paper concludes that reasonable trade-off between thermal efficiency, thermal comfort and moisture safety is difficult to reach for masonry with internal insulation and wooden floors. Sealing provisions complemented by tempering of joist pockets are considered as two key technical measures for reliable hygro-thermal performance of wooden beam ends in full-brick masonry with interior thermal insulation in cold temperate climate.