Internal Wall Insulation

Internal Wall Insulation

Internal Wall Insulation stops heat escaping by slowing down the rate at which it is lost through the walls. The insulation is applied to the internal walls as opposed to the outside; by doing this it means that the External walls of the property remain the same.

Technical Information

Internal wall insulation solutions usually involve the installation of metal or timber studs with insulation installed between the studs and then overlaid with a vapour control layer and plasterboard. Alternatively, a thermal laminate board or rigid insulation board plus plasterboard can be mechanically fixed to the walls. These systems should not be used to isolate or hide moisture penetration or damp problems in the existing structure. In accordance with Building Regulations, solid walls should prevent moisture ingress arising from exposure to rain and snow without moisture penetrating to the inside and damaging the building.

Insulating internally improves the thermal performance of the wall without affecting the external appearance of the building. However, there will be a small reduction in the internal floor area, typically only1-2%. In a large number of cases, internal wall insulation could be the preferred option because it costs less to install and maintain than external insulation systems, does not require scaffolding during the installation process, the existing appearance of the building is maintained and it provides flexibility during the refurbishment program.


The ThermoShell IWI System is a brand new internal wall insulation system designed for upgrading existing solid external walls. It consists of thermally engineered insulated studs and water repellent glass mineral wool insulation slabs, which can be combined to provide greater thicknesses of thermal insulation than achievable by using a single thickness.

EcoStuds are a composite of high performance extruded polystyrene (XPS) insulation and Oriented Strand Board (OSB). The OSB is manufactured from timber supplied from Forest Stewardship Council (FSC) certified forests. The IWI System has been designed to simplify the process of upgrading solid masonry walls while delivering high levels of thermal performance. The system can be installed by any competent builder.