uPVC stands for unplasticized polyvinyl chloride, a hard plastic material commonly used in windows and doors. The material is resistant to pollution, moisture, corrosion, and mold. This makes uPVC windows a longer-lasting alternative to timber and aluminium windows.UPVC window is one that is made from unplasticised polyvinyl chloride – that’s what UPVC stands for. This tends to be very low maintenance, which means unlike wooden or aluminium standards, you generally won’t have to spend too much time or money fixing these frames up.