Polyisocyanurate (PIR) Pipework Insulation

High-Performance Industrial Insulation for Pipes, Ducts & Process Systems

Polyisocyanurate (PIR) is a rigid, closed-cell foam insulation material designed for superior performance in industrial pipework and ductwork systems. At Thermal Clad, we specialise in supplying and installing PIR insulation fabricated into preformed pipe sections, slabs, and custom shapes. Our focus is on pipework and industrial applications, where thermal efficiency and durability are required.

The photo shows Thermal Clad’s recent project using PIR section pipework insulation and white aluminium cladding to external refrigeration pipework.

What Is Polyisocyanurate (PIR)?

Polyisocyanurate (PIR) is a thermoset plastic foam created by reacting polyols and isocyanates in the presence of blowing agents. The process produces a rigid, closed-cell structure that makes PIR one of the most effective insulation materials available. Because PIR is closed-cell and rigid, it maintains its thermal and structural performance over time rather than absorbing moisture like fibrous alternatives. PIR is manufactured CFC and HCFC-free

Key properties of polyisocyanurate (PIR):

• Thermal conductivity (λ-value): typically 0.022–0.028 W/m·K, delivering excellent insulation with less thickness.
• Closed-cell structure: resists water absorption and vapour ingress, supporting long-term performance
• Temperature range: reliable operation from –120°C to +120°C, covering cryogenic, chilled, and medium-temperature applications
• Compressive strength: high compressive and dimensional stability allow PIR to be fabricated into pipe sections and slabs without losing shape
• Density: typically 30–40 kg/m³, making it lightweight yet robust.

Why Choose Polyisocyanurate (PIR) for Pipework Insulation?

Choosing polyisocyanurate (PIR) offers distinct advantages over traditional insulation products:

• Outstanding energy efficiency – Low thermal conductivity reduces energy loss, improving system performance and lowering operating costs.
• Moisture resistance – PIR’s closed-cell structure ensures it does not absorb water, unlike some fibrous alternatives
• Durability – With proper installation, PIR pipe insulation lasts for decades, often as long as the system itself.
• Lightweight and easy to install – Reduces labour costs and speeds up installation compared to heavier mineral alternatives.
• Environmentally responsible – Manufactured CFC/HCFC-free, compliant with modern sustainability standards

Applications of Polyisocyanurate (PIR)

PIR insulation is fabricated by the manufacturers into different forms for specific uses by Thermal Clad:

• Preformed pipe sections – manufactured to fit a wide range of pipe diameters and insulation thicknesses
• Rectangular ductwork slabs – for air handling systems, HVAC units, and ventilation ducts; PIR sheets and slabs are used to insulate rectangular ductwork located externally to a building.
• Tank and vessel insulation – PIR slabs applied to large industrial tanks, refrigeration units, and process vessels.
• Custom fabrications – tailored PIR components for complex plant geometries or project-specific needs.

Industry Use Cases

• Petrochemical and chemical processing – polyisocyanurate (PIR) insulates hot and chilled pipelines, protecting workers and improving efficiency. It is widely applied to process pipework and cold services in this sector
• Refrigeration and cold storage – PIR performs at cryogenic levels down to –120°C, keeping facilities energy efficient
• Food processing and breweries – PIR keeps production lines and storage tanks consistently chilled, supporting quality and hygiene standards
• Pharmaceutical manufacturing – precise thermal control for clean, regulated production environments.
• HVAC and building services – PIR slabs insulate ductwork for large commercial and industrial buildings.

Polyisocyanurate (PIR) vs Other Insulation Materials

• Mineral wool – good fire resistance but can absorb moisture, which reduces performance; heavier and slower to install. PIR’s closed-cell structure avoids water uptake and maintains performance over time
• Phenolic foam – offers low λ-values, but can be brittle and more expensive; PIR provides a strong balance of performance, durability, and cost-effectiveness. However we would use phenolic foam for any ductwork and pipework insulation applications inside of a building, due to fire safety

Technical Specifications of PIR Pipe Insulation

• Thermal conductivity (λ-value): ~0.022–0.028 W/m·K
• Density: ~30–40 kg/m³
• Temperature range: –120°C to +120°C
• Compressive strength: high, ensuring durability under mechanical stress
• Moisture absorption: negligible, due to closed-cell structure

Manufacturer datasheets can be provided with full details on physical properties and fire classifications for verification and records

Quality, Compliance and Documentation

Thermal Clad works with trusted PIR manufacturers who fabricate cut preformed pipework sections, sheets and slabs to tight tolerances, ensuring repeatable fit and thermal continuity on site. For every project, we can supply product datasheets outlining physical properties and fire classifications so that designers and site teams can verify specification compliance. Our internal QA covers material receipt, controlled storage, verification of thickness and fit, sealing of longitudinal and circumferential joints, checks at supports and penetrations, and final inspection prior to handover. This disciplined approach helps PIR insulation deliver its design performance throughout the asset life while meeting the documentation needs of auditors and insurers.

Installation and Handling of PIR

Correct installation of polyisocyanurate (PIR) ensures long-term performance:

• Storage – Keep PIR slabs and pipe sections dry, flat, and covered to prevent weathering before installation.
• Fitting pipe sections – Ensure a close, continuous fit to minimise thermal bridging and air infiltration.
• Sealing joints – Use vapour barriers and tapes where specified to prevent condensation and moisture ingress.
• Ductwork applications – Fix slabs securely and align with vapour control layers to maintain system efficiency.
• Compliance – Always follow UK building regulations, fire safety standards, and manufacturer guidance during design and installation.

Sustainability Benefits of PIR

• Reduced energy waste – Lower heat transfer means less energy consumption and improved plant efficiency.
• Long service life – Decades of use reduce waste from replacements and maintenance interventions.
• Environmentally considerate manufacturing – Produced without CFCs or HCFCs and finished to recognised industry standards

By reducing operational carbon emissions and improving efficiency, polyisocyanurate (PIR) supports businesses working toward net-zero targets while delivering reliable performance in critical infrastructure.

Extended Guidance for Engineers and Specifiers

When selecting polyisocyanurate (PIR) for pipework insulation, consider the following engineering factors to optimise performance and lifecycle value:

• Thickness selection and U-values – Calculate insulation thickness based on process temperature, ambient conditions, allowable heat loss, and risk of surface condensation. PIR’s low λ-value allows thinner sections to meet targets.
• Vapour barriers and condensation control – On cold and cryogenic lines, pair PIR with correctly detailed vapour control to prevent moisture ingress that can compromise any insulation system over time.
• Interface with supports and fittings – Ensure continuity of insulation at hangers, valves, and flanges using preformed sections, oversize shells, and removable boxes to limit thermal bridges.
• Fire performance and classification – Review the fire classification of the selected PIR system from manufacturer datasheets and ensure the overall build-up meets project fire strategy requirements
• External vs. Internal use – While PIR is suitable for external ductwork and pipework, its use on internally located ductwork and pipework is a significant concern. Thermal Clad would ask clients, engineers and specifiers to check with the PIR manufacturer before applying the material to internal services.

Why Work With Thermal Clad?

Thermal Clad is a trusted partner for industrial insulation projects across the UK. We supply and install PIR preformed pipe sections, slabs, and custom components from leading manufacturers, ensuring consistent quality and compliance. Our teams bring deep experience across petrochemical, refrigeration, food processing, and brewing facilities, and we provide technical support from specification through to installation and QA. We also supply manufacturer datasheets with physical properties and fire classifications for engineer review and project records.

Whether you’re insulating petrochemical pipelines, refrigeration facilities, food processing plants, or HVAC ductwork, Thermal Clad delivers polyisocyanurate (PIR) solutions that combine performance, safety, and sustainability. Contact us for technical datasheets, pricing, or project advice on PIR pipework insulation.