Wind-driven rain exposure on building envelopes taking into account frequency distribution and correlation with different wall orientations

Excessive moisture inside building envelopes makes them vulnerable to moisture damages such as mould, algae growth, rot, corrosion, weathering, fading, etc. One of the main moisture sources for building envelopes is wind-driven rain (WDR). This paper characterizes the WDR for twenty-two locations in South Korea based on hourly measured weather data for 20 years and an artificial typical year from Meteonorm®. This study determines a wind-driven rain reference year using a semi-empirical method, taking into account the frequency of occurrence of the WDR and the correlation between the different wall orientations. The annual amount of the WDR shows a significant range from 125.4 kg/(m2∙a) to 904.4 kg/(m2∙a) with the individual prevailing orientations by location in South Korea. The deviations of the WDRs determined by the wind-driven rain reference year and the annual mean wind-driven rain can be characterized in two groups in terms of the amount and the distribution of the WDR. The first group has a characteristic that only the amount is changed while keeping the distribution across the wall orientations. The second group shows that the amount and the distribution are changing together. The wind-driven reference year can characterize the WDR by selecting and combining the most representative periods from the long-term measurements. By contrast, the artificial typical years from Meteonorm® hardly show any similar characteristics of the WDR determined with the long-term measured weather data.