Heatsaver is an economical 2mm thick polystyrene liner containing fire retardants that provide basic insulation as well as combating condensation problems and subsequent mould growth for a healthier home. To create a more durable and smoother surface we recommend the surface is overlined - Wallrock fibreliner is particularly tough and strong. This product is suitable as a localised ‘problem solver’ for cold external walls and is not recommended for use in fire escape routes inside your home unless the surface is further treated with a fire retardant covering. This product is class E fire rated and should not be used for projects such as new builds and extensions where Building regulations are applicable