Celotex vs Kingspan PIR Boards – What’s the Difference?

by Robert Haynes on November 09, 2025

When choosing insulation boards for your project, two of the most recognised names in the UK market are Celotex and Kingspan. Both brands produce high-quality PIR (Polyisocyanurate) insulation boards that deliver excellent thermal performance for walls, floors, and roofs. However, there are a few key differences that might affect which one you choose — particularly when it comes to cost.

Understanding PIR Insulation Boards

PIR insulation (short for Polyisocyanurate) is one of the most efficient rigid board insulation materials available. It offers a high thermal resistance (low lambda value), meaning you can achieve the same insulation performance with a thinner board compared to alternatives like EPS or mineral wool.

Both Celotex and Kingspan manufacture PIR boards using similar methods — a rigid foam core sandwiched between foil facings — which makes them lightweight, easy to cut, and suitable for multiple applications.

Where Can You Use PIR Boards?

Celotex and Kingspan PIR boards can be used across almost every area of a building, including:

Solid or cavity walls
Loft and pitched roof insulation
Flat roofs (warm roof build-ups)
Floors, including concrete slabs and timber joists
Garage conversions and home extensions

Because their thermal properties are so similar, they can often be used interchangeably — whether you’re specifying new-build insulation or upgrading an existing property for energy efficiency.

Celotex vs Kingspan – What’s the Real Difference?

Thermal performance: Almost identical. Both brands offer lambda values around 0.022 W/mK, ensuring excellent thermal resistance. Kingspan’s Therma range (TP10, TF70 and TW55) performs on par with Celotex PIR boards. Please note that this comparison refers to the Therma range and not Kingspan’s higher-end Kooltherm range.
Applications: Interchangeable. You can use Celotex and Kingspan Therma boards in the same construction types — walls, floors, roofs, and more. Celotex PIR boards match the performance of Kingspan’s TP10, TF70, and TW55 boards at a lower cost.
Quality and certifications: Both meet British and European building standards and carry BBA certification, ensuring compliance and reliability.
Installation: Virtually the same. Boards from either brand can be easily cut and fitted between studs, rafters, or joists.
Price: This is where Celotex shines. It typically offers better value for money while maintaining the same performance as the Kingspan Therma range.

Why Celotex is the Cost-Effective Choice

While Kingspan has a strong reputation in the construction industry, Celotex offers the same quality insulation at a more competitive price point. This makes it an ideal choice for trade customers, contractors, and homeowners looking to reduce costs without compromising on performance.

At Cut Price Insulation, we stock the entire range of Celotex products in popular thicknesses such as 25mm, 50mm, 75mm, 100mm and 150mm. Whether you need a single sheet for a small repair or pallet quantities for a large-scale build, we canoffer bulk discounts and to keep your project on budget.

Shop Celotex PIR Insulation Boards

Summary: Celotex vs Kingspan

Both Celotex and Kingspan PIR insulation boards are trusted, high-performance products suitable for the same applications. The Kingspan Therma range (TP10, TF70 and TW55) and Celotex PIR boards share the same installation process, thermal efficiency, and certifications — the key difference lies in pricing. With Celotex, you’ll get comparable quality at a lower cost, making it the smarter buy for those who want maximum efficiency for their money.

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