This research investigates the hygrothermal performance of cross-laminated timber (CLT) and dowel-laminated timber (DLT) constructions in combination with conventional and bio-based insulation materials, focusing on the impact of built-in moisture. Heat-Air-Moisture (HAM) simulations in Delphin software are used to assess the effects of moisture on these timber constructions. The study compares traditional CLT, which uses adhesives between layers, with DLT, a non-glued alternative. It examines how different insulation materials—conventional (e.g. expanded polystyrene) and bio-based (e.g. cellulose and wood fiber)—affect moisture transport and the ability of the timber structures to manage built-in moisture introduced during construction. The Delphin simulations form the basis to analyze moisture risks (mold growth, wood decay and degradation of the bio-based insulation) under both historical climate conditions and different climate projections. Results show that DLT exhibits improved moisture tolerance compared to CLT, due to the absence of adhesives, which allows for better moisture transport and faster drying towards the interior surface. Bio-based insulation materials contribute to more stable moisture conditions within the wall structure. They show potential for reducing risks of mold and wood decay at low initial moisture levels, especially in combination with DLT. However, for these bio-based alternatives built-in moisture has a high impact on the thermal performance.