Insulated plasterboard or, as it's sometimes known, internal wall insulation is applied to the internal walls of a building and can be mechanically fixed or adhesively bonded to the wall. It is ideal for retrofit projects and improving the thermal performance of existing solid wall buildings, particularly if you cannot insulate a building externally.
When designed and installed correctly, internal wall insulation should not lead to damp problems.
Before carrying out work, installers should carry out a pre-assessment of the building to ensure it is in good condition and dry. Installers should carefully plan and design the installation with close attention paid to junctions around features, such as windows and doors. They will also need to look carefully at junctions around the floor and ceilings and any penetrations such as joists or pipework to ensure a continuous layer of insulation and vapour protection.
As internal wall insulation applications will mean that external walls remain cold at all times, there may be cases where installers advise that solid wall insulation cannot be fitted. This may be the case where the materials used to construct the wall are particularly porous and planning restrictions prevent effective external weatherproofing.
Internal wall insulation systems can be either 'moisture open' or 'moisture closed'. Whether to use moisture open or closed materials is dependent on the specifics of a project, including its use, location, construction, condition, ventilation, moisture load and level of heating. A full assessment and development of a plan for improvement is crucial.
Page updated 02/07/2025
Moisture open systems, such as wood fibre, can allow moisture to pass in and out of the wall, preventing them from being saturated and allowing the construction to dry more easily. However, they still rely on heat escaping from the property to help evaporate moisture within the wall. This means that walls must typically be insulated to a lower level than might be preferred. These systems can also be unsuitable where the walls are likely to be exposed to severe weather conditions such as driving rain.
Moisture closed systems, such as our Kooltherm K18 Insulated Plasterboard, work on the principle of occlusion. This ensures that moisture doesn’t get trapped within the wall construction. The external leaf is designed to prevent driving rain entering the construction and a vapour control layer should also be installed internally to prevent condensation forming behind the insulation layer. A condensation risk analysis can be used to then determine whether a construction in a particular location can handle any residual interstitial condensation that might form. As moisture closed internal wall insulation systems are not reliant on internal heat to warm walls, more thermally efficient insulation specifications can be used.
For more information, see our article on moisture open or closed internal wall insulation.
The Kingspan Insulation One Stop Shop helps homeowners improve their home's energy efficiency by providing a comprehensive, end to end solution for domestic retrofit and refurbishment projects.
The Kingspan Insulation Retrofit Team can offer advice, organise assessments and manage the whole project from start to finish. They also provide access to a range of grants offered by the SEAI (Sustainable Energy Authority of Ireland) to support your home energy upgrades.
Yes, we offer two products - Kooltherm K17 Insulated Plasterboard (for both mechanically fixed and adhesively bonded insulated drylining) and Kooltherm K18 Insulated Plasterboard (for mechanically fixed drylining). Both products provide insulation, drylining and vapour control in one board. They can be used with solid stonework or brickwork, with or without an existing lining. The products have a thermal conductivity of as low as 0.021 W/mK - making them some of the thinnest commonly used insulants for internal walls. This makes them ideal for maximising the internal space of a room when installing internal wall insulation.
