No, with our PVCu casement windows we fit the trickle vents in the head of the outer frame and not the sash. When a trickle vent is specified in a casement window, we use a larger profile section for the head of the window changing it from a standard 56mm outer frame to a 78mm outer frame to incorporate the trickle vent and without compromising on the distance between the vent and your internal plaster line.