Hygrothermal behavior of wood fiber insulation, numerical and experimental approach

Many new insulation materials are being developed and thermally tested aiming at understanding and improving their insulation characteristics in order to improve the energy performance of new and existing buildings. Bio-sourced materials appear among the new insulation solutions presenting the advantage of being able to save energy on one hand and having a low environmental impact on the other. The wood fiber material is one of the most successful natural insulation materials being recently used in building constructions. It presents many advantages besides its insulation performance; due to its density, it stores moisture thereby improving the indoor air quality; it is also an excellent acoustic insulator because it has a natural tendency to absorb and reduce sounds. In order to evaluate its effectiveness in building applications, this study analyzes the hygrothermal modelling and performance of the wood fiber insulation in building applications by adopting two approaches: A numerical approach using a mathematical model that describes heat and mass transfer within the wood fiber material being considered as porous media. The hygrothermal characteristics of the wood fiber material are first determined experimentally for this purpose, namely the thermal conductivity, the heat capacity, and the isotherms of sorption and desorption. An experimental approach is carried out in controlled and uncontrolled ambiance conditions in order to validate the numerical model. A 50 cm x 50 cm wood fiber sample having an 8 cm thickness is tested for this purpose. A very high accordance is observed between the measured and modelled results for both the temperature and the relative humidity evolutions within the sample at x = 2 cm and x = 4 cm with a mean difference (Delta T) over bar of 0,21 degrees C at x = 4 cm and 1 degrees C at x = 2 cm. The maximum recorded differences for the relative humidity are: 5,5% and 4,5% at x = 2 cm and 4 cm respectively. The ability to predict the thermal and the hygric behavior of the wood fiber insulation will thus allow a better understanding of the efficiency of natural insulation materials.

Automated summary

Wood fiber material is a successful natural insulation material, providing good insulation performance and improving indoor air quality by absorbing and reducing sounds due to its high density. The ability to predict the thermal and hygric behavior of wood fiber insulation contributes to a better understanding of the efficiency of natural insulation materials.