An onset is given to whole building modelling for investigating the impact of wind-driven rain (WDR) on the hygrothermal response, indoor climate and mould growth at interior wall surfaces of historical brick wall buildings. First the WDR load on the facades of a 4×4×10 m3 tower is numerically determined. Then the hygrothermal behaviour of the brick wall is numerically analysed on a horizontal slice through the tower. The simulations demonstrate that the impact of WDR loads on the moisture contents in the walls is much larger near the edges of the walls than at the centre. For the case analysed, the absorption and transmission of WDR forms an important moisture source for the indoor environment, and may cause increases of indoor relative humidity in summer and winter, which can reach up to 55 % in winter. The increased thermal conductivity and latent heat effects due to WDR loads yield an increase of 18.7 % in total heating energy consumption in winter; while a much smaller impact on indoor humidity and a very small impact on energy consumption are seen in spring and autumn. Finally, the obtained relative humidity and temperature at the interior wall surfaces are combined with isopleths of generalised spore germination time of fungus mould. The comparison of the results with the WDR load to those without WDR shows significant WDR impacts on mould growth in summer and winter and much smaller impacts in spring and autumn. The results also explain that WDR impacts on mould growth are more pronounced at the edges of the walls than at the centres.