Insulation for Solid Walls
U-value CalculatorStart your U-value calculation >
For homeowners looking to improve the performance of their solid masonry walled properties - perhaps to achieve compliance with modern building regulations, or perhaps to go beyond that and meet a retrofit standard such as EnerPhit - adding more insulation material to the outer face of the wall is sometimes not possible.
Using an insulated plasterboard product such as Celotex PL4000, either adhered to the masonry inner surface or mechanically fixed to timber battens that are themselves fixed to the masonry inner surface, represents a potential option for improving the thermal efficiency of the wall without affecting its external appearance. Another option is a PIR insulation board (Celotex TB4000 or GA4000 can be considered) alongside a separate layer of plasterboard. Lightweight polyisocyanurate (PIR) foam boards from Celotex are easy to handle, and their thermal efficiency means thicknesses can be kept to a minimum, reducing lost floor space
As part of a holistic approach to upgrading, you will also want to consider building fabric, airtightness and controlled ventilation along with improvements in thermal performance. For Celotex PL4000, the composite facing on the insulation board, behind the plasterboard layer, can form part of the air and vapour control layer when the tapered edge plasterboards are taped and jointed.
Alternatively, the solid masonry wall can have timber battens or studwork mechanically fixed to it and the stud zone insulated with a glass mineral wool roll or slab prior to being finished with a suitable air and vapour control layer (AVCL) and plasterboard. In cases where the solid masonry wall is narrower than 200mm, the timber studwork may need to be stood-off the solid masonry wall by 50mm rather than being fixed directly to the wall.
In all cases, specialist advice should be sought in relation to the correct solution for the solid wall for each individual property, especially in relation to moisture movement and the potential of condensation. Breathable membranes and dynamic hygrothermal calculations may need to be considered.
When using Celotex or ISOVER products, you need to satisfy yourself that use of the product meets all relevant national Building Regulations and guidance as well as local, national and other applicable standards relevant for your construction or application, including requirements in relation to fire and applicable height restrictions. In addition to the product datasheet, please refer to the following product documents:
- BBA certificates - where applicable to the application
- Declarations of Performance
- Health & safety datasheets
Celotex products should not be used in the external walls of buildings over 18 metres in height (England and Wales) or 11 metres in height (Scotland). Recent changes to Building Regulations mean that only non-combustible insulation or insulation of limited combustibility can be used in buildings of that height.
The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.
|Product Name||Thickness Range||Sizes||Lambda|
|Celotex TB4000||20-40mm||Width 1200mm, Length 2400mm||0.022 W/m.K|
|Celotex GA4000||50-100mm||Width 1200mm, Length 2400mm||0.022 W/m.K|
|Celotex PL4000||25-65mm (+12.5mm Plasterboard)||Width 1200mm, Length 2400mm||0.022 W/m.K|
|ISOVER Steel Frame Infill Batt||50-100mm||Width 600mm, Length 1200mm||0.036 W/m.K|
|ISOVER Unislab||50-140mm||Width 400mm or 600mm, Length 1200mm||0.036 W/m.K|