Prestige combines aluminium’s clean lines with exceptional thermal performance for up to an A+ Window Energy Rating.* Our innovative Thermlock® multi-chamber thermal design, hidden away inside each window and door, helps keep you and your property well insulated against the worst of the UK weather. This closed-cell, insulating chamber acts as a thermal break and works in conjunction with high performance glazing to create class leading thermal performance, far superior to traditional polyamide thermal breaks. Sheerline’s cills also feature this same technology coupled with innovative in-built weather sealing keeping draughts and rain safely outside.