Thermal bridging analysis of connections in cross-laminated timber buildings based on ISO 10211

Cross-laminated timber (CLT), developed in Europe for the utilization of low-grade wood, is an engineered wood product (EWP) with high carbon storage and low carbon emissions. CLT wooden houses have advantages such as reduction of greenhouse gases, shortening of construction period through precast and modular construction, improved of insulation performance and airtight performance, the realization of the high-rise wooden house. In this study, ply-laminate cross-laminated timber (ply-lam CLT) was prepared using domestic plywood as the core material of CLT, and the thermal properties and heat transfer performance of ply-lam CLT were analyzed. The thermal conductivities of the ply-lam CLT in the radial, tangential, and longitudinal directions were 0.104 W/(m K), 0.111 W/(m K), and 0.122 W/(m K), respectively. The results of the heat transfer analysis through ISO 10211 indicated that the ply-lam CLT walls had lower thermal bridges than wood frame structure walls. Moreover, the ply-lam CLT walls with exterior insulation had lower thermal bridges. In addition, the self-tapping screw (STS) joining method on all connections was able to maintain excellent insulation performance because of low thermal transmittance coefficient. In addition, it should be noted that the STS applied from inside overlapped with the geometric thermal bridges.