Environmental energy is being studied actively around the world due to the effects of climate change, global warming, and energy policies. Energy policies are being reinforced to reduce building energy consumption. Therefore, environmental-friendly and sustainable building materials have been used to reduce energy consumption. The cross-laminated timber (CLT) wall is an environmental-friendly material that stacks layers at right angles, and bonds them together to form large solid panels. However, there is no standard for CLT structure walls in Korea. This study focuses on analyzing the hygrothermal properties of the CLT wall by showing the water content of the CLT wall, mold growth risk of CLT by WUFI simulation, and energy load by DesignBuilder using the climatic conditions of Seoul, Korea. CLT walls Ext_EPS, Ext_FG, and Ext_EPSFG based on an external insulation system, and walls Int_EPS, Int_FG, and Int_EPSFG based on an internal insulation system, were prepared for simulation analysis. The total water content (TWC) of Wall Ext_EPSFG was measured to be 8.67 kg/m2, which was the lowest TWC. This indicates that the TWC of the external insulation system wall is lower than that of the internal insulation system wall. Furthermore, the water content (WC) of structure based on the external insulation system is lower than that based on the internal insulation system. This indicates that the WC of Wall Ext_FG, measured to be a maximum 8.69% of WC, is lower than Wall Int_EPS, measured to be a maximum 10.45% of WC. According to the risk of mold growth, this indicates that all of the CLT wall layers have low mould growth risk, and the maximum mould index of walls Ext_FG and Int_EPSFG was measured to be 0.019. As a result of the hygrothermal analysis in this paper, CLT walls based on an external insulation system are more suitable than the internal insulation system. Therefore, this study analyzed the energy consumption of CLT walls based on the external insulation system, which was found to be lower than the energy consumption of the internal insulation system walls. (C) 2019 Elsevier Ltd. All rights reserved.