Interior panel selection for light-timber structure buildings under intermittent energy use: Balancing mould risk and energy efficiency

Light-framed timber structure (LTS) buildings are increasingly utilized in the hot summer and cold winter climate zone due to their renewability, energy efficiency, and low carbon footprint. However, heat and moisture transfer (HAMT) within the building envelope becomes highly complex under the intermittent energy consumption mode commonly adopted in this region, impacting energy performance, indoor environmental creation, and moisture risk prevention. In these processes, interior panels, serving as the primary pathway for HAMT between indoor environment and building envelopes, play a critical but often overlooked role in mould prevention and moisture regulation. To assess the comprehensive impacts of energy consumption mode and identify the optimal strategy for interior panels, this study employed numerical simulations conducted using WUFI-Plus, validated through in-situ experimental data. Results showed that, although intermittent modes met indoor hygrothermal requirements only about 25 % of the time and were less effective in controlling temperature and relative humidity compared to continuous modes, they significantly reduced mould growth risks by leveraging daytime ventilation while achieving a 72.0 % reduction in annual energy consumption. Interior panels with high water vapour permeability helped lower envelope moisture content and improve humidity control, though they may also induce moisture fluctuations. Inorganic materials with moderate vapour permeability are thus recommended as a balanced choice. This study highlights the value of considering interior panel configuration in tandem with typical operational modes, providing practical guidance for hygrothermal optimisation of LTS buildings in humid climates.