Expanded Polystyrene Boards
While these are suitable for insulating floors, they do not insulate as effectively as other materials when used for external wall insulation, so a greater thickness is required to insulate an external wall. This type of insulation material can give off toxic gases in the event of a fire, so particular care must be taken to ensure it is sealed in correctly, which is difficult around door and window frames.
Phenolic Foam Boards
Phenolic foam boards offer better insulation than expanded polystyrene, so a thinner layer of insulation can be used to offer the same amount of insulation which is particularly important when retro-fitting homes.
This material is rather like the fibreglass roll in your loft, but compressed into hard workable pads or panels. Mineral wool has a similar thermal rating to polystyrene but has much better fire proofing qualities.
Polyisocyanurate, also referred to as PIR, polyiso, or ISO, is a thermo set plastic typically produced as a foam and used as rigid thermal insulation. It has a high thermal efficiency, so the panels are relatively thin.
Fixing External Wall Insulation
On level walls, the boards can be fixed using plastic plugs and anchor bolts. On walls which are not even and level, a bonding adhesion coat is used to level the boards. Once the bonding has been left to set for 24 hours, plugs and pins are used to further secure the boards.