PIR Insulation Board

What is PIR Insulation?

PIR (Polyisocyanurate) insulation is a rigid, high-performance thermal insulation board engineered from a robust, closed-cell foam.

Its unique structure, formed by trapping a specialised low-conductivity gas within countless tiny, sealed cells, makes it an efficient barrier against both heat loss in colder months and heat gain in warmer periods.

This allows for the achievement of excellent thermal performance with relatively thinner insulation boards compared to many conventional materials.

Applications

• Roofs:
  • Pitched Roofs: Commonly installed between rafters, over rafters (creating a "warm roof" where the insulation is above the structural timber, keeping the roof space within the thermal envelope), or a combination of both.
  • Flat Roofs: Used in both warm flat roof constructions (insulation placed above the structural deck and under the waterproofing layer) and inverted flat roof systems (insulation placed above the waterproofing membrane, often with ballast).
• Walls:
  • Masonry Cavity Walls: Available as partial-fill or full-fill boards, designed to fit neatly within the cavity between masonry leaves, enhancing the thermal performance of traditional wall constructions.
  • Timber Frame & Steel Frame Walls: Integrated within the studwork or as an external sheathing layer to provide continuous insulation, reducing thermal bridging.
  • Solid Wall Insulation: Applied to the internal face (often as insulated plasterboard laminates) or as part of an External Wall Insulation (EWI) system on the external face of solid masonry walls, significantly improving the thermal efficiency of older buildings.
• Floors:
  • Solid Ground Floors: Installed either above or below the concrete slab to prevent heat loss to the ground.
  • Suspended Timber Floors: Fitted between or below timber joists.
  • Underfloor Heating Systems: While PIR itself is not a heating element, it acts as a highly effective insulating layer beneath underfloor heating systems, ensuring that heat is directed upwards into the living space, improving the system's efficiency and response time.
• Specialised and Industrial Applications:
  • Composite Panels: Forms the insulating core of pre-fabricated sandwich panels used for rapid construction of industrial, commercial, and agricultural buildings.
  • HVAC Ductwork: Utilised to insulate heating, ventilation, and air conditioning (HVAC) ducting to minimise heat loss or gain during air distribution.

Benefits

• Thermal Efficiency (Low Thermal Conductivity): With typical values ranging from 0.021 to 0.024 W/m·K, PIR is among the most thermally efficient insulation materials available. This allows for reduced insulation thickness to achieve target U-values, maximising usable floor space.
• Fire Performance: PIR insulation is engineered to offer improved fire safety characteristics. When exposed to fire, it tends to form a robust, stable char layer on its surface, which can help to reduce flame spread, inhibit the release of burning droplets, and produce very limited smoke. This contributes to the overall fire rating of the building.
• Moisture Resistance: The predominantly closed-cell structure of PIR foam renders it highly resistant to water absorption and water vapour transmission. This property ensures that its thermal performance remains uncompromised in damp conditions and helps protect the building structure from moisture-related issues like mould.
• Lightweight, Rigid, and Durable: PIR boards are strong, stable, and lightweight, facilitating easy handling, cutting, and rapid installation on site. They exhibit excellent dimensional stability, resisting sagging, slumping, or settling over time, maintaining consistent thermal performance throughout their lifespan.
• Versatility in Application: Manufactured with various facings and in diverse formats (e.g., general purpose boards, cavity wall boards, insulated plasterboards, floor boards, flat roof boards), PIR can be effectively integrated into virtually every part of a building's thermal envelope.
• Long-Term Performance: When correctly specified and installed within the building fabric, PIR insulation boasts a very long service life, often exceeding 50 years, ensuring sustained energy efficiency and comfort for the duration of the building's life.

Understanding PIR Board Facings

PIR insulation boards often come with different facing materials on their surfaces, and understanding these can be important for your project:

• Foil Facings (Low-Emissivity): These are the most common. The multi-layered aluminum foil not only enhances the board's thermal performance by reflecting radiant heat, but it also acts as an excellent vapour control layer (VCL). This is crucial for preventing moisture from moving through the insulation and condensing within the building structure. When using foil-faced PIR, ensuring all joints are correctly taped and sealed is essential for the VCL to be effective.
• Glass Tissue Facings: Some PIR boards feature non-woven glass tissue facings. These are typically designed for specific applications where adhesion to certain glues or membranes is required, or where a less reflective surface is preferred. They may or may not provide the same level of vapour resistance as foil facings.
• Bitumen-Coated Facings: Specialised PIR boards for flat roofing systems often have a bitumen-coated glass fibre facing. This allows for direct bonding or torching-on of bituminous waterproofing membranes, ensuring compatibility and a robust roof build-up.
• Composite Facings (e.g., Plasterboard Laminates): As mentioned earlier, PIR can be pre-bonded with plasterboard, forming a composite panel that simplifies internal insulation and finishing in a single step. These are designed for direct internal application.

Choosing the right facing is vital for the correct integration of the PIR board into your specific construction assembly and to ensure optimal performance of the entire system.

Installation Best Practices

While professional installation is always an option, PIR insulation is quite DIY-friendly. Here are some tips to ensure effective and safe installation:

• Accurate Cutting: PIR boards can be cut precisely using a fine-toothed saw, a sharp utility knife, or a hot wire cutter. Measure accurately to ensure a snug fit.
• Minimising Gaps: The key to effective insulation is creating a continuous thermal layer. Ensure boards fit tightly together. Use specialist insulation tape (often foil-backed) to seal joints between boards and around structural elements like rafters or joists. Expanding foam designed for insulation can also be used to fill small, irregular gaps.
• Vapour Control: Many PIR boards come with foil facings that act as a vapour barrier. Ensure these facings are intact and joints are sealed to prevent moisture from condensing within the wall or roof structure.
• Protection: Always store PIR boards in a dry place, protected from direct sunlight and rain, before and during installation.
• Safety Gear: Wear safety glasses, gloves, and a dust mask (FFP2) when cutting or handling PIR to protect against dust and irritation. Work in a well-ventilated area.

Environmental Impact and Sustainability

• Reduced GWP Blowing Agents: Manufacturers now predominantly use blowing agents with very low Global Warming Potential (GWP), significantly lowering the product's environmental footprint.
• Long-Term Carbon Savings: The primary environmental benefit of PIR lies in its long-lasting thermal performance. By drastically reducing energy consumption for heating and cooling over the building's lifespan (often 50+ years), it prevents far more carbon emissions than are embodied in its manufacture.
• EPDs: Many manufacturers provide Environmental Product Declarations (EPDs), offering transparent, third-party verified information on the product's environmental performance throughout its lifecycle.

How PIR Insulation is Made

While the chemistry behind PIR is complex, the manufacturing process can be understood as a continuous, precise operation:

• Mixing the Ingredients: Liquid chemical components (polyol and an isocyanate, along with a special "blowing agent" and other additives) are carefully measured and mixed.
• Foaming and Rising: This mixture is then dispensed onto a moving conveyor belt, often on top of a specialised facing material (like foil). A rapid chemical reaction causes the liquid to expand and foam up, like a fast-rising dough.
• Forming Closed Cells: As it foams, countless tiny, individual cells are created within the material. These cells trap the low-conductivity gas, giving PIR its excellent insulating properties.
• Bonding with Facings: The expanding foam bonds firmly to the facing materials on both its top and bottom surfaces. These facings are important for the board's final performance, such as acting as a vapour barrier or providing a reflective surface.
• Curing and Hardening: The foam then travels through a heated section where it fully cures and hardens into a strong, rigid board.
• Cutting to Size: Finally, the continuous slab of rigid PIR is cut into the standard board sizes and thicknesses that you see available for purchase.