Rainscreen duo slab is a dual density insulation board with a rigid outer surface and a resilient inner face that is engineered for use in extreme weather conditions. Thermal insulation for ventilated rainscreen and overcladding applications that is effective and non-combustible. Rainscreen duo slab is a dual density slab designed for use as insulation behind rainscreen cladding systems as well as sealed cladding systems like curtain walls and other over cladding systems. When built, the Rainscreen duo slab will securely butt join together, preventing extraneous heat loss that can be caused by gaps in some insulations. Rainscreen duo slab needs less fixings due to its unusual dual density structure, making it a cost-effective option for over cladding applications. Rainscreen duo slabs are lightweight and quick to cut with a sharp knife into any form. They are shrink wrapped in polyethene and delivered on pallets with a waterproof hood suitable for outdoor storage. The product can be left unprotected for an extended period of time after installation due to their durable outer facing surface before the rainscreen cladding is added. With a Vapour resistivity of 5.9 MNs/gm. The slabs, therefore reduce the risk of condensation, allowing natural drying out of the structure. As a result, the slabs reduce the possibility of condensation, allowing the structure to dry naturally. It contains a fire rating of Euroclass A1 non-combustable to EN 13501-1 and is BBA certified.