PIR Insulation Board

Frequently Asked Questions

What is Celotex PIR Insulation Board?

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.

How to Install Celotex Insulation Board

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 vs Recticel

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.

Celotex U-Value Calculator

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.

Why Choose PIR Insulation Board for Your Floors?

PIR (Polyisocyanurate) insulation board delivers unmatched thermal efficiency in compact thicknesses, making it the intelligent choice for floor applications where space is precious. With thermal conductivity values as low as 0.022 W/mK, these boards provide superior performance compared to traditional materials, helping you achieve Building Regulation compliance with minimal floor build-up.

Our floor insulation range features premium products from:

Celotex GA4000 Series - Industry-leading thermal performance with excellent compressive strength
Recticel Eurothane - Proven reliability with enhanced moisture resistance
Kingspan Kooltherm K108 - Cutting-edge phenolic technology for exceptional efficiency
Jablite Jabfloor 70 - Robust polystyrene solution for heavy-duty applications

Expert Solutions for Every Project

Whether you're renovating a Victorian terrace or constructing a modern extension, we stock the precise thickness you need. From 25mm boards for space-critical renovations to 200mm solutions for new-build compliance, our comprehensive stock ensures your project moves forward without delays.

Popular applications include:

Ground floor solid slab insulation
Suspended timber floor upgrades
Underfloor heating installations
Commercial and residential new builds

The DIY Building Supplies Difference

Quality you can trust - We exclusively stock products from established British manufacturers like Celotex, Kingspan, and Recticel, ensuring consistent performance and full warranty support.

Expert guidance included - Our technical team provides U-value calculations, fixing specifications, and installation advice to ensure your project achieves optimal performance.

Competitive pricing guaranteed - Direct relationships with manufacturers mean you get trade-quality materials at prices that work for your budget.

Fast, reliable delivery - With stock held at our Nottingham facility and nationwide delivery network, your materials arrive when promised.

Start Your Project Today

Every successful insulation project begins with the right material specification. Contact our technical team for expert advice on achieving your thermal targets, or browse our comprehensive range below to find the perfect PIR insulation board solution for your requirements.