A badly oriented vent lets rain in or blows an unpleasant draught. On a uPVC window, the fitting direction follows simple, consistent rules.

The golden rule: fins sloping down on the outside

Outside, the canopy (or hood) is fitted with its fins facing down to deflect rain. Inside, the air-inlet grille is mounted with slots facing up: fresh air is thrown towards the ceiling, where it mixes with warm air without creating a draughty feeling.

Position on the window

On the top rail of the sash or frame: the standard location, which optimises air diffusion
The slot is usually cut as two oblong openings of roughly 172 × 12 mm, depending on the inlet model
Never fit the grille low down: cold air would drop straight into the room

Why you should never block vents

In a home with mechanical ventilation, window air inlets are the entry point of the air-renewal circuit: blocking them causes condensation, mould and degraded indoor air. If you feel an excessive draught, replace the grille with a self-regulating or humidity-controlled model rather than sealing it.

Our teams replace air inlets, grilles and accessories during their window and roller shutter work throughout Île-de-France.