This study analysed the bonding mechanisms and strength between wood and non-wood implants in producing laminated oak-wood beams. The suitability of different types of adhesives, namely for load-bearing and general purpose, was also analysed. Three different types of non-wood implants—carbon fibres, glass fibres, and aluminium were glued with epoxy resin (ER), thermoplastic 1-k polyurethane adhesives (PUR), structural polyurethane adhesives (PUR 2 and PUR 3), and polyvinyl acetate (PVAc) adhesives and bonds were tested for shear strength (SS) according to ISO 6238:2018. Results of the bond quality expressed as the ultimate load to failure and displacement were recorded using the universal mechanical testing machine in combination with the digital image correlation (DIC) method. Before the shear test, all the samples were conditioned in dry and wet climatic conditions. Test results indicated that the application of PUR adhesives for bonding carbon and glass fibres with oak wood could sufficiently replace two-component ER, which is generally recommended for such purposes but is very challenging to utilise in industrial conditions. PVAc adhesives proved efficient only for combination with AL implants and in dry conditions. Aluminium sheets were shown to require surface pre-treatment, such as sanding and degreasing or a different type of adhesive to achieve sufficient adhesion.

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.

Wood as a building material is a good thermal insulator, but in thin wood coverings this is not an obstacle to heating when the heating system is placed directly under the top layer. This study investigated the influence of a safety extra-low-voltage power supply (12 V and 24 V) on the surface temperature, response time and heat distribution of wood covering elements with an integrated heating system. Sixteen oak–plywood elements with copper heating wires 3 mm below the walking surface were tested in daily heating cycles; two of them were insulated with reflective foil or aerogel. At 12 V, the surface reached 29.1 ± 0.5 °C (about 5.6 K above ambient), within the comfort limit for floors, while at 24 V it reached 38.6 ± 1.3 °C (p < 0.001) and local checks appeared on the oak surface. The differences between elements were three times larger at 24 V (4.3 K compared with 1.5 K), but the relative non-uniformity was the same (CV of 8.5% at 12 V and 9.0% at 24 V; r = 0.98). Insulation under the element increased the temperature rise of the surface by 15–19%, while the type of insulation had little effect. A 12 V power supply is therefore a safe and sufficient solution for heating with wood coverings in nearly zero energy buildings.