Dependence of the insulating behavior of some common woods to the pore network and packing density of their fibers: a microstructural approach

Thermophysical and microstructural behavior of eleven tropical woods widely available and commonly used was investigated. Experimental measurements of thermal conductivity and thermal diffusivity of wood were performed using the heat flow meter and transient plane source technique. The results show values in the range of 0.2–0.37 mm2/s for thermal diffusivity and 0.12–0.34 W m−1 K−1 for thermal conductivity. The correlation between the thermal conductivity and parameters as porosity, pore size distribution, intensity ratio of lignin and microstructure was drawn. The thermal conductivity of wood decreases with the increase in pores volume (vp). For vp > 70%, the values are between 0.1 and 0.15 W m−1 K−1 and reach 0.23 W m−1 K−1 for vp between 40 and 60%. For dense woods with the vp less than 40%, the values are between 0.24 and 0.35 W m−1 K−1. The results show experimental values of the effective thermal conductivity of wood species closer to the values of parallel model. The presence of ray and parenchyma which appear perpendicular to the axis of the fibers in the structure of the wood species makes it difficult to have straight correlation. This suggests that heat flux which travels through the matrix of wood follows a very complex road linked to the microstructural features of each class of wood. These results appear as significant contribution for the future development of sustainable energy technologies in relation to the prediction of energy saving and building energy metering.