Investigation on the influence of the panel composition on selected properties of three-layer solid wood panels

The coefficient of thermal conductivity, the equilibrium moisture content, the in-plane swelling and the water vapour resistance of laboratory-produced three-layer solid wood panels of Norway spruce wood were tested. The coefficient of thermal conductivity is in the range of 0.09-0.11 W/m . K in normal climate. The voids in the middle layer (slots, spaces between the lamellas) cause a slight decrease of the coefficient of thermal conductivity. The orientation of the growth rings has an effect on the thermal conductivity as well. The water vapour resistance is affected by the orientation of the growth rings in the layers and the voids in the middle layer. The equilibrium moisture content above a relative humidity of 35% is slightly below the one of solid spruce wood. The equilibrium moisture content of solid wood panels with a middle layer of wood-based material is smaller because of its lower equilibrium moisture content compared with solid wood.