Modus PVCu Windows and Doors. Modus is the UK’s first fully integrated window and door system, available with three sash design options. The standard rebate, slim rebate and fully flush sash styles offer developers a much wider range of design aesthetics. 50% of the Modus frames are made from post-consumer recycled PVC-U, from our dedicated Eurocell recycling facility. EurocellPLC.