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Thermally modified wood is becoming an increasingly popular material for different applications in buildings. Laboratory tests indicated a positive effect of thermal modification on durability, dimensional stability and thermal conductivity of wood. Therefore, windows and facade elements made of thermally modified Norway spruce and non-modified Norway spruce were tested in the field and installed in different test objects which were exposed at five locations in Europe (Slovenia, Germany, Sweden, and Spain). Results from monitoring showed that elements and windows made of thermally modified spruce (TMS) had considerably lower wood moisture content compared to the ones made of non-modified spruce and that wax further positively influenced moisture performance. Colour changes of TMS were more intensive compared to non-modified spruce but were successfully retarded by adding pigments to the wax. Mould and stain growth was largely dependent on the location, amount of precipitation and relative humidity. [ABSTRACT FROM AUTHOR]

The load-carrying capacity of a timber structure is highly dependent on the strength of its connections. Very limited information exists on the thermal degradation, or the properties at elevated temperatures, of such connections. This insufficient information is one of the major impediments for modeling elevated temperature performance for wood-frame structures. The objective of this study was to characterize thermal degradation of yield load capacity of single-shear nailed connections between wood and oriented strand board (OSB) as a function of time and temperature. The mechanism of degradation was explained using first order kinetics. Using the principles of time–temperature superposition (TTS), predictive models for connection capacity degradation were developed. A total of 450 wood-to-OSB connections were tested laterally after exposure to nine different elevated temperature regimes. The degradation of yield load strength over time occurred at a constant linear rate. Temperature dependence of this rate was modeled using the Arrhenius activation energy theory. Using Arrhenius activation energy theory and principles of TTS, a master curve was developed to predict the performance of connections after exposure to a temperature of 150°C. The predictions matched well with independent experimental observations. The master curve developed using TTS provides predictive estimates of residual capacity in a connection as well as its failure times. [ABSTRACT FROM PUBLISHER]

The major aim of this study was to create a numerical model of thermal bridges in a wooden structure and to discover differences between factual values of linear thermal transmittance utilized in the finite-element (FE) modelling and values given by the European normative method (EN ISO 14683). Thermal bridges of wooden structures were detected using thermocamera FLIR S65 for infrared detection. These measurements allow displaying the temperature distribution of the thermal scan and proving the positive correlation between heat flux and change in the evaluated temperatures of a thermal bridge. A three-dimensional FE model of the structure was prepared for the thermal analysis using the engineering software ANSYS Workbench 13. The transmission heat loss coefficients of a prefabricated wooden house were established based on the Czech normative method (ČSN 730540-4). Linear thermal transmittance values calculated from the thermal analysis and the normative method given by EN ISO 10211 were compared. The results show that even if the transmission heat loss coefficients meet the requirements designated by standards, the real heat losses are increased by thermal bridges involved in the construction. Their influence is determined by the linear transmittance value which is usually not exactly established. [ABSTRACT FROM PUBLISHER]

This study aimed to evaluate physical and mechanical properties and colour changes of fast-growing Gympie messmate wood subjected to two-step steam-heat treatments. To achieve this, Gympie messmate wood was thermally treated under different conditions. Combined steam (127°C and ∼0,1471 MPa) and heat treatments in an oven (180–240°C for 4 hours) were performed. Physical and mechanical properties were evaluated by weight loss, equilibrium moisture content, specific gravity, volumetric and linear swelling and static bending tests, while colour changes were studied using CIEL*a*b*technique. The main findings showed that the steam pre-treatment in autoclave influenced most of the technological properties evaluated, mainly for heat treatments performed in low temperatures (180–200°C). The most significant changes after thermal treatments were observed for dimensional stability, which increased as a function of temperature of treatment. On the other hand, mechanical strength of thermally modified wood was significantly affected, while stiffness did not change. Colour modifications due to the application of two-step steam-heat treatments confirm the possibility to using these samples for aesthetic purposes. [ABSTRACT FROM PUBLISHER]

Two Malaysian hardwoods, acacia (Acacia mangium) and sesendok (Endospermum malaccense), that had been subjected to oleo-thermal modification were studied to determine their sorption isotherm behaviour using a dynamic vapour sorption apparatus. All the specimens were thermally modified using palm oil at three different temperatures (180, 200 and 220°C) and three different times (1, 2 and 3 h). The results showed that there was a reduction in equilibrium moisture content at each target relative humidity due to the heat treatment, but that the two wood species showed different behaviour in this respect. The adsorption isotherms were analysed using the Hailwood and Horrobin model, with excellent fits to the experimental data. The monolayer water and polylayer water were both reduced at a range of relative humidity values of the treated samples, although behaviour between the two wood species differed. Heat treatment resulted in an increase in hysteresis ratio, which was probably due to the increase in matrix stiffness of the cell walls. [ABSTRACT FROM AUTHOR]