Evaluation of the risk of decay of wooden beams embedded in internally insulated walls by long-term measurements

Belgian Building Research Institute, Energy Division, Av. P. Holoffe 21, 1342 Limelette, Belgium

^* Corresponding author: timo.de.mets@bbri.be

Abstract

Internal insulation of existing walls is crucial to increase the energy efficiency of the building stock. However, this technique influences the drying potential of the wall and could consequently increase the decay risk of wooden beams embedded in the existing wall. We performed a long-term field study on different test walls with wooden beams. This paper discusses 2.5 years of measurements by analysing the moisture contents at the beam ends for the different test walls. The use of vapour open insulation materials has only a slightly favourable impact. On the other hand, measures to lower the moisture content of the wall have a significant effect, either by locally interrupting the insulation at the beam junction or by applying a water repellent treatment. Controlling the rain load on the wall seems to be a key point towards a moisture-safe application of internal insulation with embedded wooden beams.