Experimental investigations of wooden beam ends in masonry with internal insulation: results contrasting three years of the experiment

This paper deals with hygro-thermal performance of wooden beam ends embedded in masonry walls with lime-cement plaster applied on the external side. Three different insulation systems are attached on the internal side of masonry. The real scale experiment has been monitored for three consecutive years. Microclimatic conditions in joist pockets were assessed by VTT mold growth index. The paper shows the influence of two changes of boundary conditions on the microclimate in joist pockets. First, moisture load on the internal side of building enclosure was increased (24 °C, 60 % in winter 2016/2017 instead 20 °C, 50 % in winter 2015/2016). Then, the artificial short-time rain event brought liquid water onto the external surface of building enclosure in July 2017. The rain intensity was chosen so as to mimic the intensive summer thunderstorm. The increase of water vapor concentration in the air on the internal side led to suitable conditions for mold growth in unsealed joist pockets of a vapor open insulation system. On contrary, microclimate in sealed joist pockets in both vapor open and vapor closed insulation systems stayed in acceptable levels with no mold growth. The artificial rain event significantly changed the hygro-thermal performance of joist pockets. Drying season was shortened and the relative humidity in joist pockets overtook the time profile of external relative humidity