6 Boards x 90mm Celotex Thermaclass Cavity Wall 21 Insulation - 1190mm x 450mm

Celotex is a brand of Polyisocyanurate (PIR) insulation board - a type of rigid foam insulation board backed with a foil layer, ideal for its exceptional thermal performance. It is a strong and light type of foam insulation board that keeps structures warm by trapping air inside. PIR insulation is lightweight, durable, and offers excellent fire resistance and thermal insulating properties, making it a super DIY-friendly solution that can easily be cut to size to fit rafters, joists and stud walls, and used as Cavity Wall Insulation. We also sell a Celotex PIR Insulated Plasterboard which is ideal to save time in stud wall applications. 

Due to it’s versatile nature, there are many different uses for PIR Insulation and therefore many different ways to correctly install it. However, generally PIR insulation should be purchased to fit the depth of the cavity or space it is to fill. It can be cut to size to fit the height and width of cavities, joists and rafters using a sharp utility knife or handsaw for thicker boards. It is typically designed to be friction-fit to a space, meaning the boards should fit tightly and stay easily in place with no additional fixtures and fittings.

For precise installation instructions for your specific use case, it is recommended to consult your builder, architect or building inspector to ensure installation complies with building regulations. 

Celotex and Recticel are both brands of foil-faced PIR Insulation board available in a range of thicknesses. They are comparable products made from similar materials and methods and from a construction perspective they have the same Fire Rating (Euroclass F Reaction to Fire classification, according to BS EN 13501-1)  and thermal conductivity value of 0.022 W/m.K and so are suitable for largely the same purposes and projects. 

Use the Celotex U-Value Calculator to help calculate the correct u-value of your project to ensure it complies to all of the required building regulations.