Improving Durability of Wooden Beam Bearings in Inside Insulated Walls by Tempering the Beam’s Heads

Abstract

Improving durability of wooden beam bearings after a thermal renovation via interior insulation is highly demanding for planners. Because of an isolated thermal bridge in the area of the wooden beam head the risk of condensation water forming in this area increases after installing interior insulation. The problem with wooden beam ends has been analysed increasingly in the last few years by many research institutions as wooden ceiling constructions are common in existing buildings. Furthermore, thermal renovation makes a vital contribution regarding improving the energy-efficiency of existing buildings. In this paper a method to temper wooden beam ends is introduced. It is a patent pending which is currently developed further using laboratory-prototypes in a double climate chamber. This technology is based on thermo conductive types of sheet metal, which are driven into the construction at the joint between the wooden beam and the surrounding masonry. The thermal energy is provided by a heating pipe and fed into the metal. Because of the metal's high thermal conductivity, heat can be fed specifically into the beam's end in order to avoid wood rotting at this crucial point. Calculating the beam's end temperature control was done using three-dimensional HAM simulations with air flows in the ceiling cavity being taken into account. The results of different measurements in the double climate chamber as well as the HAM simulations clearly show that the durability of an interior insulation can be increased via a temporary and local tempering of wooden beam bearings. At the same time the risk of wood rotting at the ceiling's bearing structure is minimised. Comparative analyses show that this method of tempering the beam ends is especially energysaving as the energy input is low due to the special feeding of heat via thermo conductive types of sheet metal.

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

“…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 (23 °C, 60 % RH). Sealing of joist pockets together with tempering, either performed passively [6] or actively [7], could be two necessary technical measures for moisture safety of joist pockets. For instance, suitable metal profiles could be used as strengthening and also conducting elements bringing heat from internal environment into the joist pocket.…”