Estimation of the exposure of buildings to driving rain in Spain from daily wind and rain data

In this study, the severity of the exposure of buildings in Spain to driving rain is estimated. The annual driving rain index (αDRI) is determined at 80 sites spread across Spain, based on wind and rain data recorded daily over 30 years. The comparison among the driving rain indices based on daily, monthly and annual climatic data, allows assessing the existence of co-occurrence errors and errors due to averaging. This work also introduces a new reference scalar index to characterise exposure to driving rain during the wetting stages of the building façades based on daily data. Therefore, a new approach to the concept of spell established by the ISO 15927-3:2009 standard is proposed. The combination of the two indices provides a qualitative characterisation based on two temporal criteria, supplementing the estimated exposure level currently set by the Spanish standard for the design of buildings. A driving rain map for Spain is produced. Those sites where exposure during periods of wetting is significant are identified (the northern part of the country, the Gulf of Cadiz and specific areas of the Mediterranean coast and the Canary Islands). An important annual exposure on the north and northwest coast of the country and a slightly lower exposure in coastal areas of the Gulf of Cadiz are also identified. The Mediterranean coast and the interior regions are considered to have a low annual exposure to driving rain. Finally, the major findings of this research are reported.