Insulation for Solid Walls

2020 SGIUK External solid wall (IWI)
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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.

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.


Key Considerations

When using Celotex 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:

Celotex products should not be used in the external walls of buildings over 11 metres in height. Recent changes to Building Regulations mean that only non-combustible insulation or insulation of limited combustibility should 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.

Insulation products
Product Name Thickness Range Sizes Lambda
Celotex TB4000 20-40mm Width 1200mm, Length 2400mm 0.022
Celotex GA4000 50-100mm Width 1200mm, Length 2400mm 0.022
Celotex PL4000 25-65mm (+12.5mm Plasterboard) Width 1200mm, Length 2400mm 0.022