150mm Insulation Board

150mm Insulation Board Types and Applications

A 150mm insulation board is a high-performance specification, typically chosen when thermal resistance is the priority and build-up depth is not a constraint. At this depth, a single layer of PIR or phenolic board can deliver the thermal resistance levels associated with low-energy and high-specification new build projects, making it a common choice for ground floors in passive-standard builds, deep rafter roof constructions, and heavily insulated wall systems. Insulation UK stocks the full range of rigid insulation boards at 150mm from all the leading manufacturers, with competitive trade pricing and fast UK-wide delivery on every order.

150mm PIR Insulation Boards

PIR insulation board at 150mm is the most commonly specified product in this category. Delivering a thermal conductivity of 0.022 W/mK in a foil-faced, lightweight format, these boards are suitable for solid and suspended floors, framed wall systems, pitched roof applications, and flat roof warm deck build-ups.

If Celotex is your preferred option, then the XR4150 is the product of choice at this thickness, sitting in their XR (extra resistance) range and designed specifically for projects where a superior level of thermal performance is required. For floor insulation in particular, Kingspan ThermaFloor TF70 is widely used beneath screed and above ground-bearing slabs, and is compatible with underfloor heating systems. Kingspan ThermaWall TW55 is the go-to board for timber and steel frame wall systems, while Kingspan ThermaPitch TP10 is a standard specification for between-rafter and below-rafter pitched roof work. Recticel Eurothane GP, Ecotherm Eco-Versal, and Unilin PIR complete the range, all sharing the same thermal performance characteristics.

150mm Phenolic Insulation Boards

Where a project requires maximum thermal efficiency within a constrained build-up, phenolic boards at this depth outperform PIR in an identical profile. Kingspan Kooltherm K103 achieves a thermal conductivity of 0.019 W/mK and is widely used for floor insulation where minimising the impact on finished floor levels is a priority. For pitched roofs and loft conversions, Kingspan Kooltherm K107 provides the same performance advantage for between-rafter installations.

150mm Polystyrene Insulation Boards

EPS Insulation Boards 150mm

Expanded polystyrene is a competitively priced option for floor and external wall insulation where the very highest thermal efficiency is not the primary concern. Jablite Jabfloor EPS70 achieves a thermal conductivity of 0.038 W/mK and is BBA certified for domestic ground floor construction. The graphite-enhanced Jablite HP+ range improves on this with a lambda of 0.030 W/mK, offering better performance in the same footprint. Higher compressive strength grades are also available for commercial and industrial floor applications.

XPS Insulation Boards 150mm

Extruded polystyrene at this thickness provides the combination of high compressive strength and negligible moisture uptake required for basement walls and heavily loaded floor slabs. Ravatherm XPS 300SB is available at 150mm for domestic and medium load-bearing floor and basement wall applications, delivering long-term performance in wet or damp conditions where PIR or EPS would not be appropriate.

Where is a 150mm Insulation Board Used?

Walls

Rigid boards at this depth are specified in high-performance timber and steel framed wall systems where a single thick layer is preferred over a multi-layer approach. Celotex XR4150 and Kingspan TW55 are both regularly used in this application and can contribute substantially to achieving demanding wall U-value targets under Part L.

Floors

This is one of the most common applications for 150mm rigid insulation boards. Celotex XR4150 and Kingspan TF70 are frequent choices below screed or between suspended floor joists in high-specification new build projects. Jablite EPS and Ravatherm XPS provide alternatives where compressive strength or moisture exposure are the deciding factors.

Pitched Roofs and Loft Conversions

For deep rafter constructions and loft conversions with generous rafter depth, 150mm PIR and phenolic boards can often satisfy the full between-rafter specification in a single layer. Kingspan TP10 and Kooltherm K107 are both well-established in this application, with phenolic boards offering a clear performance advantage where rafter depth is limited.

Flat Roofs and Below-Ground Applications

Ravatherm XPS 300SB at 150mm is suited to below-slab and basement perimeter applications where sustained moisture exposure and imposed loads rule out PIR or EPS. For flat roofs, PIR boards at this thickness are used in warm deck build-ups where a high level of thermal resistance is required in a single layer.

Why Choose Insulation UK for 150mm Insulation Boards?

Competitive Trade Pricing Some of the most competitively priced 150mm rigid insulation boards available online, with no minimum order value.

All the Leading Brands Celotex, Kingspan, Recticel, Ecotherm, Unilin, Jablite, and Ravatherm all stocked at this thickness and available at trade prices.

Fast UK-Wide Delivery Reliable delivery across the UK, with free shipping on orders over £500 (ex VAT).

Expert Technical Support Our team has over 50 years of experience in the insulation industry. For our customers and yours, our priority is to provide guidance, a sense of security and peace of mind, ensuring your projects run as expected from idea to finished job.