• High-precision testing and empirical characterization of three WRBs • Spatial modeling of WRBs with quantified moisture transport properties • Wall configuration and climate effects on the severity of WRB performance outcomes • System-level mould index comparison for three wall types and four climates • Seasonal mould-index peaks analyzed across the wall types and climates . Water-resistive barriers (WRBs) are essential in building envelope systems, especially in wood-frame structures where moisture-related decay is a major concern. This study delivers a detailed experimental characterization of three WRB membranes, spun-bonded polyolefin (SBPO), a self-adhesive film, and building paper, quantifying key transport properties such as vapor permeability, liquid diffusivity, moisture storage, and saturation content using high-precision gravimetric methods. The moisture-dependent functions were integrated into DELPHIN hygrothermal simulations, and mould growth risk was assessed using the VTT model across varying wall configurations and climates. The results show that although material properties like vapor permeability and liquid diffusivity strongly influence wall moisture behavior, they are not sufficient on their own to ensure effective moisture control. Wall design and climate conditions also play a critical role in determining overall performance. Results show that in cold-wet conditions, wall types I and III incorporating the high vapor-resistance SBPO membrane exceeded the ASHRAE 160 mould index threshold of 3.0 at the outer OSB surface, indicating visible mould potential. In the warm-humid climate, Wall Type II showed a marked increase in mould index at the inner OSB surface, as the drying direction reverses relative to cold climates. Under these conditions, it behaved oppositely to Types I and III, with greater inward moisture accumulation. These results first show that mould severity is higher on the outer surface of OSB; second, show that WRB vapor resistance influences the magnitude of mould index in a climate-dependent manner, higher resistance increased mould severity in cold climates by limiting outward drying, while in warm-humid climates higher liquid water transport governed mould accumulation due to inward drying. Moreover, the timing of mould peaks was controlled by climate and wall configuration rather than membrane selection. These results, derived from precise laboratory measurements and system-level simulations, form the core contribution of this research and support a data-driven framework linking WRB properties to wall durability while guiding membrane selection across different climates and wall designs. .

• Extensive wind tunnel experiments were conducted on SSV via a roof opening. • A benchmark dataset with generic models was created with varied configurations. • Links were built between free-end flow separation and ventilation mechanisms. • Flow pattern above a high-plan aspect ratio cuboid was studied across yaw angles. • Marked enhancement of ventilation was observed with presence of conical vortex. Previous studies have rarely addressed single-sided ventilation driven by the external flow over the roof, which exhibits strong potential owing to its highly turbulent nature and strong suction associated with leading-edge flow separation. In this study, wind tunnel experiments on single-sided ventilation through a roof opening were conducted using two isolated generic models: a cylinder and a rectangular prism, each with a set of replaceable openings. Both models were tested either flush- or floor-mounted. Two inflow conditions, each with three free-stream velocities, were considered. For both models mounted beneath the floor, the nondimensional ventilation rates ( Q* ) are comparable to values reported in the literature; for the prism, a slight increase in Q* with orientation suggests the development of a mixing layer along the streamwise extent of the floor-level opening. In the floor-mounted configuration, body-induced flow disturbances tend to enhance ventilation. Three primary governing rooftop flow regimes are identified—recirculation zone, flow reattachment, and conical vortex—whose relative dominance over the opening depends on inflow turbulence, wind incidence angle, and model configuration. When the opening lies entirely within the recirculation zone, Q* is proportional to the normalized local fluctuation intensity, with a coefficient of about 0.16. For certain yaw angles, the marked increase in Q* strongly correlates with the presence of a conical vortex over the prism model roof, which features strong suction and intense fluctuations. Direct advection through the opening could occur with a favorable opening size and location, allowing deep penetration of the reattaching shear layer.