This Eurovent document specifies a method for measuring the water rejection performance of louvres, subject to simulated rain and wind pressures, both with and without air flow through the louvre test. For the purpose of this test, a 1000 mm x 1000 mm section of wether louvre or the nearest possible blade increment is to be tested. The first edition of Eurovent 2/5 was published in 1985. Since that time, the work has been carried out in the CEN/TC 156, in order to prepare a new European Standard needed to support essential requirement of EC Directives. The present edition, approved by Eurovent WG 2, is conform to the projected European Standard. This document is available in English.