LAUSR

Abstract ISO standard 15927-3 establishes two calculation methods to characterise wind-driven rain exposure on building facades, with different approximations according to the available climatic data: (i) a reference method, using hourly wind and rain data, and (ii) an alternative method using average wind records and the present weather code for rain in half-day intervals when hourly data are not available. However, the equivalence between the two methods was only validated in three British cities with similar environmental conditions (London, Manchester, and Edinburgh), and for only four facade orientations. In addition, the description of the second method also admits different interpretations that can influence its results. This study re-examines the real equivalence between the two methods, comparing their results in multiple facade orientations of 12 Spanish locations subjected to varied amounts of wind-driven rain exposure. The analysis shows that the reliability of the method based on non-hourly data varies significantly according to the methodological interpretation applied, making it advisable to review its current description. Finally, an improvement is proposed that reinforces the equivalence and reliability of the alternative method with respect to the reference method, regardless of the climate of the analysed location.