2. Watertightness

In contrast to the air barrier, which merely limits the passage of air through the sash-to-sleeper connection, the water barrier must be watertight up to a given pressure (called p _max in test standard NF EN 1027).

To achieve a watertight seal between the sash and frame, the following three elements are required:

• water barrier in the outer plane of the leaf ;

• intermediate space to channel and drain water seeping into the profiles ;

• air-permeability barrier behind this interspace.