Innovative Solutions: Comparative Study of Laboratory and In Situ Measurements of Thermal Properties of Bark Insulated Exterior Walls

The study aimed to investigate the thermal storage potential of oak tree bark as a natural and easily accessible material and to examine the possibility of incorporating this raw material into external prefabricated walls. The U-values of oak tree bark were compared with mineral wool (MW), which is a standardized and well-known insulating material. Oak tree bark, a residual material, is mainly used as an energy source. However, in light of actual green policies at the European Union (EU) level, raw wood and its components, e.g., bark, should be used for long-lasting products and not as an energy source. According to the Croatian Technical Regulation on the Rational Use of Energy and Thermal Insulation in Buildings, the maximum U-value for external walls in Croatia is 0.30 W/m2K. Here presented test results show that the U-values of the experimental wall compositions were 0.22 W/m2K for the wall with mineral wool (MW) and 0.29 W/m2K for the wall with oak tree bark. Despite mineral wool having a thermal conductivity (λ, W/mK) 53% lower than the experimental tree bark, walls with bark fulfill the national insulation requirements; therefore, they present an alternative and sustainable insulation option. Furthermore, the Blower door test (n50 value) of the bungalow was measured to be 3.75 h−1, proving the potential of tree bark as an alternative eco-friendly insulation material in exterior walls. However, further investigations are necessary in order to create and optimize the panel, its thickness, density, adhesive technology, the size of bark particles, production parameters, etc., as these influence properties of the final product to be placed on the market.

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