Numerical analysis of hygrothermal properties and behavior of Korean based cross-laminated timber (CLT) wall system to deduce optimal assemblies

Cross Laminated Timber (CLT) is attracting worldwide attention, due to its durability, usability, and many other advantages. However, since CLT is made of timber, analysis of the hygrothermal performance is essential. In this study, the basic hygrothermal values are measured to obtain the exact hygrothermal performances. The values are put into the simulation with various assemblies which has hygroscopic effects. The effectors are the type of insulation, the presence of the vapor retarder, the climate condition and the type of standards. The final goal of this paper is to find the optimal CLT assemblies. The thermal conductivity, thermal transmittance coefficient, and water vapor resistance factor were measured. The thermal transmittance coefficient of the wall system was measured by using TCi and facing thermo-hygrostat, and applied in the simulation. The water vapor resistance was measured by conducting dry-cup test. In addition, the various conditions that affect the thermal moisture behavior were applied to the simulation for getting stable hygrothermal results. As a result, the standard of Passive house and Domestic wooden house, the climate condition, the presence of breathable water proofing paper, and the insulation alternatives of Expended Polystyrene (EPS) and Extruded Polystyrene (XPS) were applied. It was concluded that breathable waterproofing paper should be installed inside, and the applications of both XPS and EPS made no difference to moisture but the application of Mineral Wool was adversely affect to hygrothermal performance of the CLT wall system. The thickness of insulation should be designed according to the Passive house standard (0.15 W/m²K) rather than the Domestic (Korea) Wooden house standard (0.21 W/m²K).