Influence of glued-in reinforcement profiles on the thermal characteristics of wooden window profiles

Abstract

Nowadays wooden windows represent high aesthetic value to modern buildings. There is a strong trend of increasing their dimensions, especially their height, which causes problems considering their stability and load bearing capacity. Aluminium, stainless steel, carbon-fiber reinforced polymer profiles and glass-fiber reinforced polymer profiles, with different geometry and orientation, were used to reinforce wooden window mullion. Since reinforcing materials have usually higher thermal conductivity as wood, their effect on the thermal performance of the window as a whole, was examined in this study. Thermal transmittance of several different reinforced profiles was analyzed to select an optimal solution. It was concluded that reinforcing material does not have significant effect on thermal transmittance of window frame, if reinforcement is not placed through the entire thickness of the window profile. If this is the case, only glass-fiber reinforced polymer, with a maximum of 22 % reinforcing material in window profile, fulfils the standard criteria for low energy buildings. The effect of type and geometry of reinforcing materials have minor effect on thermal transmittance of entire window, but have great impact on the minimal local inside surface temperatures, which can lead to condensation and mould growth.