Louvre window and door is a window blind or shutter with horizontal slats that are angled to allow light and air, but to keep out rain and direct sunshine. The angle of the slats may be adjustable, usually in blinds and windows, or fixed. allow air to flow through almost 100% of the window area.  Louvre window and door is a window blind or shutter with horizontal slats that are angled to allow light and air, but to keep out rain and direct sunshine. The angle of the slats may be adjustable, usually in blinds and windows, or fixed. allow air to flow through almost 100% of the window area.