PIR insulation is a rigid foam insulation board made from polyisocyanurate, a thermoset plastic polymer created through chemical reaction between isocyanates and polyols. PIR boards consist of closed-cell foam (95%+ closed cells) with typical thermal conductivity of 0.022 W/mK, density of 30-35 kg/m³, and compressive strength of 100-200 kPa depending on grade, making them the most widely specified rigid insulation in UK residential construction for walls, roofs, and floors. The material’s combination of excellent thermal performance per millimetre thickness, adequate structural strength, moisture resistance, and straightforward installation explains its dominance in meeting Part L Building Regulations requirements.

Definition of PIR Insulation

PIR stands for polyisocyanurate, a type of plastic foam used as thermal insulation in building construction. The name comes from the chemical structure of the polymer forming the foam’s cell walls.

Basic Definition

PIR insulation is a rigid board consisting of:

• Foam core made from polyisocyanurate polymer
• Closed-cell structure (individual cells are sealed)
• Facings bonded to both board surfaces (usually aluminium foil or glass tissue)
• Low-density material (30-35 kg/m³ typical)
• Excellent thermal insulation properties (0.022 W/mK lambda value)

What Makes PIR Different from Other Insulation

Unlike fibrous insulation (mineral wool, glass wool) which consists of interwoven fibers trapping air, PIR consists of solid foam with millions of tiny sealed cells. This structural difference gives PIR distinct properties:

Rigidity: PIR boards maintain their shape without external support. You can walk on them, cut them with hand tools, and install them in positions where fibrous insulation would slump or compress.

Moisture resistance: The closed-cell structure prevents water penetration. PIR maintains thermal performance in damp conditions where fibrous insulation would saturate and lose effectiveness.

Compressive strength: PIR boards carry loading (like floor screed and finishes) without compressing. Fibrous insulation compresses under loading, reducing thickness and thermal performance.

Thermal performance: PIR achieves better insulation per millimetre than most alternatives. The 0.022 W/mK lambda value means less thickness needed for equivalent thermal resistance compared to mineral wool (0.035-0.044 W/mK) or EPS (0.031-0.038 W/mK).

Common Names and Terminology

PIR insulation goes by several names in UK construction:

PIR boards: Standard term Rigid insulation boards: Generic term covering PIR and alternatives Celotex: Brand name often used generically (like “Hoover” for vacuum cleaners) Kingspan: Another brand name sometimes used generically Polyiso: Shortened form of polyisocyanurate, common in technical literature

Technically, “Celotex” and “Kingspan” are specific brand names, though trade professionals often refer to any PIR board using these brand names regardless of actual manufacturer.

How PIR Insulation is Manufactured

Understanding PIR manufacturing helps explain the material’s properties and performance characteristics.

Raw Materials

PIR foam forms from two main liquid components:

Component A (Isocyanate): A chemical compound containing isocyanate groups. This provides the “I” in PIR. The most common isocyanate used is MDI (methylene diphenyl diisocyanate).

Component B (Polyol blend): A mixture containing polyols (molecules with multiple hydroxyl groups), catalysts, blowing agents, flame retardants, and other additives. The polyols provide part of the polymer structure.

These components are liquid at room temperature. When mixed, they react chemically to form solid polyisocyanurate foam.

Manufacturing Process

Step 1: Mixing Components A and B are precisely metered and mixed together. The ratio and mixing quality critically affect final foam properties. Industrial mixing equipment ensures consistent, thorough mixing.

Step 2: Pouring The mixed liquid is poured or sprayed onto a moving production line between two facings (typically aluminium foil). The facings will become the board’s top and bottom surfaces.

Step 3: Reaction and Expansion Chemical reaction begins immediately. The mixture heats up (exothermic reaction) and expands, creating foam. The reaction involves:

• Polymerization (linking molecules into long polymer chains)
• Foaming (blowing agent creates gas bubbles forming cells)
• Curing (polymer solidifies into rigid structure)

This happens rapidly – the foam rises to design thickness within 1-2 minutes.

Step 4: Curing The foam continues reacting and curing over the next several minutes to hours. Initial cure happens quickly on the production line. Final cure completes over 24-48 hours.

Step 5: Cutting Once sufficiently cured, the continuous foam is cut into standard board sizes (typically 2400x1200mm) using large saws. Edge waste is trimmed and usually recycled back into the manufacturing process.

Step 6: Aging Boards are aged before packaging. During aging, some of the blowing agent gas in cells diffuses out while air diffuses in. This gas exchange stabilizes thermal performance. The declared lambda value (0.022 W/mK) accounts for this aged performance, ensuring real-world performance matches specifications.

The Closed-Cell Structure

The manufacturing process creates a closed-cell foam structure. Each tiny cell (typically 0.1-0.3mm diameter) is sealed, preventing gas exchange between cells. This closed-cell structure provides:

Low thermal conductivity: The gas trapped in cells has lower thermal conductivity than air Moisture resistance: Water can’t penetrate sealed cells Structural integrity: Closed cells give the foam rigidity and strength Dimensional stability: The foam maintains size and shape over time

Approximately 95% of cells in PIR foam are closed. The small percentage of broken or interconnected cells (5%) results from manufacturing variables but doesn’t significantly affect performance.

Facing Application

Most PIR boards have facings bonded to both surfaces during manufacturing:

Aluminium foil facings: Most common. Provide vapour resistance, reflective properties reducing radiant heat transfer, and improved surface strength. The foil is thin (typically 40-50 microns) but provides useful benefits.

Glass tissue facings: Used for boards intended for torch-applied roofing felt applications. Glass tissue withstands the heat of torching without melting (aluminium foil would melt).

Other facings: Some specialist products use coated, textured, or composite facings for specific applications.

Facings are bonded during foam formation. The liquid foam adheres to facings as it expands and cures, creating strong bonds.

PIR Thermal Performance Explained

PIR insulation’s thermal performance comes from its physical structure and the gases trapped within cells.

Understanding Thermal Conductivity

Thermal conductivity (lambda value, measured in W/mK) indicates how readily heat flows through a material. Lower values mean better insulation.

PIR achieves 0.022 W/mK (some products declare 0.023 W/mK). This means for every 1 metre thickness of PIR, with 1 Kelvin temperature difference across it, 0.022 Watts of heat flows through each square metre.

For perspective:

• Air: 0.026 W/mK (PIR performs better than still air)
• Mineral wool: 0.035-0.044 W/mK
• Timber: 0.13 W/mK
• Concrete: 1.35 W/mK

How PIR Achieves Low Thermal Conductivity

Three factors combine to give PIR excellent thermal performance:

Factor 1: Low-conductivity gas in cells During manufacturing, the blowing agent gas (typically a hydrocarbon blend or HFC) fills the cells. These gases have lower thermal conductivity than air. Over time (during aging), some gas diffuses out and air diffuses in, but significant low-conductivity gas remains, contributing to performance.

Factor 2: Cell structure The foam consists of millions of tiny closed cells. Heat must conduct through thin polymer cell walls rather than convecting through open space. This cellular structure limits heat transfer paths, reducing overall conductivity.

Factor 3: Reflective facings Aluminium foil facings reflect radiant heat, reducing heat transfer across air gaps adjacent to the board. In cavity constructions or where boards face air spaces, this reflection contributes measurably to overall thermal performance.

Thermal Performance Stability

PIR maintains consistent thermal performance over its service life:

Temperature stability: PIR’s lambda value remains consistent across typical building temperature ranges (-20°C to +80°C). Unlike some materials that lose effectiveness at temperature extremes, PIR works equally well in cold and warm conditions.

Aging characteristics: The declared lambda value accounts for gas diffusion during aging. Real-world performance matches design calculations because aging has occurred before the product reaches site.

Moisture stability: If PIR gets damp during construction (rain exposure), it maintains thermal performance once dried. The closed-cell structure prevents moisture retention affecting long-term performance.

Calculating Thermal Resistance

Thermal resistance (R-value, measured in m²K/W) indicates how much insulation a material provides. Higher R-values mean better insulation.

R-value = Thickness (metres) / Lambda (W/mK)

For 100mm PIR: R-value = 0.100 / 0.022 = 4.55 m²K/W

This R-value contributes to overall building element U-value (which accounts for all layers in a construction, not just insulation). For Part L compliance, U-value matters more than R-value, but understanding R-value helps compare insulation thicknesses and materials.

PIR vs PUR: Understanding the Difference

PIR and PUR are closely related materials often confused. Understanding their relationship and differences matters for specifications and product selection.

What PUR Insulation Is

PUR (polyurethane) insulation consists of polyurethane foam rather than polyisocyanurate. The manufacturing process is similar – mixing isocyanates with polyols – but the chemical reaction produces different polymer structures.

PUR foam has:

• Similar closed-cell structure to PIR
• Similar thermal conductivity (0.022-0.025 W/mK)
• Similar physical properties (density, compressive strength)
• Slightly different chemical composition

Chemical Difference Between PIR and PUR

The difference comes down to polymer chemistry:

PUR (Polyurethane): Forms when isocyanates react with polyols creating urethane linkages. The reaction produces polyurethane polymer chains.

PIR (Polyisocyanurate): Forms when excess isocyanate reacts with itself creating isocyanurate rings in the polymer structure. PIR formulations use more isocyanate relative to polyol than PUR formulations.

This chemical difference sounds significant but produces materials with very similar practical properties.

Practical Differences

For trade professionals, the practical differences between PIR and PUR are minimal:

High-temperature performance: PIR handles slightly higher temperatures than PUR before softening. PIR can handle +80°C continuous use, PUR typically +70°C. This rarely matters in building applications.

Fire performance: PIR achieves slightly better fire performance than PUR due to higher isocyanurate content. Both typically achieve Class E, but PIR may resist ignition slightly better.

Dimensional stability: PIR maintains dimensions at high temperatures slightly better than PUR. Again, this rarely matters for normal building applications.

Thermal conductivity: Essentially identical for building applications (both around 0.022 W/mK).

Why PIR Dominates UK Construction

PIR has largely displaced PUR in UK building insulation markets. Manufacturers primarily produce PIR rather than PUR for building applications because:

• Better high-temperature performance suits UK fire regulations
• Slightly better long-term dimensional stability
• Manufacturing efficiency with modern production processes
• Market standardization around PIR specifications

When you purchase “rigid foam insulation boards” in the UK, you’re almost certainly getting PIR rather than PUR, even if product literature doesn’t explicitly state which.

Product Naming Confusion

Some product literature uses “PUR/PIR” or “polyurethane/polyisocyanurate” as if they’re the same. This reflects:

• Similar chemical origins (both from isocyanate/polyol reactions)
• Very similar practical properties
• European standards (BS EN 13165) covering both under one standard

For specification purposes, treat them as equivalent. Any differences are too small to affect building performance or product selection decisions.

Key Properties of PIR Insulation

Understanding PIR’s key properties helps specification and recognizing when PIR suits applications.

Thermal Conductivity: 0.022 W/mK

PIR provides excellent thermal performance per millimetre thickness. 100mm PIR achieves R-value of 4.55 m²K/W, equivalent to approximately 150mm mineral wool or 160mm EPS.

This performance advantage matters where space is limited. In floor insulation, the difference between 100mm PIR and 160mm EPS can be the difference between a project being viable or creating unacceptable steps at doorways.

Compressive Strength: 100-200 kPa

PIR boards resist compression under loading. Compressive strength varies by grade:

• Wall/roof grade: 100-120 kPa (adequate for applications without direct loading)
• Floor grade: 120-150 kPa (standard for residential floors beneath screed)
• Enhanced strength: 150-200 kPa (for commercial applications with higher loading)

For reference, 120 kPa equals 12 tonnes per square metre. This easily handles residential floor loading including screed, finishes, furniture, and occupants.

Compressive strength matters primarily for floor applications where insulation sits beneath screed. For walls and roofs, compressive strength is less critical since boards don’t carry significant loading.

Density: 30-35 kg/m³

PIR foam has low density compared to many building materials. A 100mm PIR board weighs approximately 9-10kg for a 2400x1200mm sheet (2.88m²).

This low density makes boards manageable for manual handling. One person can lift and position boards during installation. Compare this to some insulation alternatives with higher densities requiring two-person handling for large boards.

Moisture Resistance: Very Good

The closed-cell structure gives PIR excellent moisture resistance. Water absorption is negligible even with direct water contact. If boards get wet during construction (rain on uncovered materials), they don’t absorb water and maintain thermal performance once dried.

This moisture resistance makes PIR suitable for:

• Normal construction applications with weather exposure during installation
• Above-grade applications where occasional condensation might occur
• Protected below-grade applications (with proper waterproofing and drainage)

PIR isn’t suitable for unprotected below-ground applications with sustained ground water contact. For those applications, XPS (extruded polystyrene) provides superior moisture resistance.

Fire Performance: Class E

PIR typically achieves Class E fire rating per BS EN 13501-1 (European fire classification system). Class E indicates:

• Material is combustible
• Limited contribution to fire spread
• Adequate for most residential and commercial building applications when used as part of complete constructions

PIR’s combustibility matters for some applications:

Buildings under 18m: PIR works in walls, roofs, floors without restriction (when properly detailed)

Buildings over 18m: Post-Grenfell regulations restrict combustible materials in external wall build-ups. For high-rise buildings, check current guidance before specifying PIR in external walls.

For standard residential construction (typically under 18m height), Class E fire performance is adequate and PIR suits all applications meeting fire regulations.

Dimensional Stability: Excellent

PIR boards maintain dimensions across temperature and moisture variations. The foam doesn’t expand or contract significantly with temperature changes, preventing gaps opening between boards.

Testing shows dimensional change under 2% when exposed to 70°C and 90% relative humidity – conditions more extreme than normal building service conditions. This stability ensures installed insulation maintains designed thickness and joints stay tight over the building’s lifetime.

Operating Temperature Range: -50°C to +80°C

PIR maintains structural integrity and thermal performance across typical building temperature ranges. The lower limit (-50°C) covers any realistic cold conditions in UK construction. The upper limit (+80°C continuous) covers normal building applications including:

• Under dark roofs in summer (which can reach 60-70°C)
• Around hot water pipes or heating systems
• In roof voids during hot weather

For applications requiring higher temperature resistance (some industrial processes), alternative materials might be needed. For building insulation, PIR’s temperature range is more than adequate.

Common Applications for PIR Boards

PIR insulation suits virtually every insulated building element in UK residential and commercial construction.

Ground Floors

Solid concrete floors: PIR boards lay above the concrete slab and damp-proof membrane, beneath screed. 100mm PIR achieves Part L compliance (0.18 W/m²K) for ground floors in typical constructions.

The build-up: concrete slab → DPM → 100mm PIR → perimeter edge strip → 65mm minimum screed → floor finish

Suspended timber floors: PIR boards fit between floor joists (supported on battens), above joists (beneath floor deck), or below joists (in underfloor void) depending on construction type and retrofit constraints.

Floor applications require appropriate compressive strength (120 kPa minimum for beneath-screed installations). Wall-grade PIR (100 kPa) isn’t suitable for floors beneath screed but works fine between or above joists where boards don’t carry loading.

Cavity Walls

PIR boards install against the inner leaf blockwork in partial-fill cavity wall construction. 75-100mm PIR maintains a 50mm residual cavity for water drainage while achieving Part L compliance (0.26 W/m²K).

Typical build-up: 100mm blockwork inner leaf → 75mm PIR → 50mm cavity → 102mm brick outer leaf

The residual cavity provides drainage path for any water penetrating the outer leaf. Full-fill cavity insulation (filling the entire cavity) is less common and requires specialist products designed for full-fill use.

Internal Wall Insulation

For insulating existing solid walls from inside (common in retrofit when external wall insulation isn’t possible), PIR boards fix to the internal wall surface beneath plasterboard finish.

Typical build-up: existing solid wall → 75-100mm PIR mechanically fixed → vapour control layer → service cavity/battens → 12.5mm plasterboard → decoration

Internal wall insulation loses internal floor area. A 100mm PIR system takes approximately 120-130mm of room width when plasterboard and battens are included. This matters for room sizes, door/window reveals, and overall space perception.

Pitched Roofs

PIR works in multiple pitched roof configurations:

Between rafters: Boards fit friction-tight between roof rafters. Common approach maintains roof void as accessible loft space. 100mm between 150mm rafters achieves 0.19-0.21 W/m²K depending on complete build-up.

Above rafters: Boards sit on top of rafters beneath roof covering (warm pitched roof). Eliminates rafter thermal bridging achieving superior thermal performance. 140-150mm PIR above rafters achieves 0.13-0.15 W/m²K.

Combined approach: Many specifications use 100mm between rafters plus 50-75mm over rafters, achieving excellent U-values (0.12-0.15 W/m²K) without excessive single-layer thickness.

Flat Roofs

PIR is the standard insulation choice for warm flat roof construction. Boards sit above the structural deck beneath waterproofing membrane, keeping the entire roof structure warm.

Typical build-up: structural deck → vapour control layer → 120-140mm PIR → waterproofing membrane

120-140mm PIR in flat roofs achieves the 0.16 W/m²K requirement for roofs under Part L 2021. The exact thickness depends on deck type and whether the build-up includes other thermal resistance contributions.

External Wall Insulation (EWI)

PIR boards can form part of external wall insulation systems, though phenolic boards are sometimes preferred for EWI due to thinner required thickness in limited build-out depth.

PIR fixes to external wall surfaces with mechanical fixings or adhesive, then render or cladding finishes over the insulation. 90-100mm PIR achieves good thermal performance for solid wall retrofit.

PIR Insulation Advantages and Limitations

Understanding both advantages and limitations helps appropriate specification.

Advantages of PIR Insulation

Best practical thermal performance per thickness: At 0.022 W/mK, PIR provides better thermal performance than most common alternatives (mineral wool, EPS, XPS). Only phenolic foam achieves better performance (0.018-0.020 W/mK) but at significantly higher cost.

This performance advantage matters where space is limited – floor-to-ceiling heights, floor level constraints, cavity widths, ceiling depths all limit maximum practical insulation thickness. PIR achieves required U-values in less thickness than alternatives.

Adequate compressive strength for floors: Floor-grade PIR (120 kPa minimum) handles residential floor loading without compression. The boards maintain designed thickness under screed and floor finishes, ensuring thermal performance matches calculations.

Good moisture resistance: Closed-cell structure prevents moisture affecting thermal performance. If PIR gets wet during construction, it maintains performance once dried. This contrasts with fibrous insulation which loses effectiveness when saturated.

Dimensional stability: PIR maintains dimensions across temperature and moisture variations. Boards don’t warp, bow, or shrink over time, maintaining tight joints and consistent thermal performance throughout the building’s lifetime.

Straightforward installation: PIR cuts cleanly with standard hand tools. Boards install quickly without specialist equipment. One person can handle and position boards easily. Installation efficiency reduces labour costs compared to some alternative insulation types.

Wide availability: PIR boards stock at most builders merchants in common thicknesses. Multiple manufacturers (Celotex, Kingspan, Recticel, Ecotherm, others) produce similar products, ensuring reliable supply and competitive pricing.

Proven track record: PIR has been used in UK construction for decades. Its performance, durability, and compatibility with standard construction methods are well-established.

Limitations of PIR Insulation

Higher material cost than EPS: PIR costs more per square metre than expanded polystyrene insulation. For applications where thickness isn’t constrained, EPS might provide better material cost value. However, PIR’s thinner requirement often means fewer boards needed, offsetting some cost difference.

Combustible material: PIR achieves Class E fire rating – it’s combustible. For buildings over 18m or situations requiring non-combustible materials, mineral wool becomes necessary. Post-Grenfell fire safety focus means combustibility affects specification decisions for some applications.

Not suitable for unprotected below-ground use: While PIR resists moisture well for above-ground applications, it’s not ideal for below-ground applications in direct contact with soil and ground water. XPS provides better long-term moisture resistance for those situations.

Limited thickness availability compared to EPS: PIR manufactures economically up to approximately 200mm thickness. For applications requiring very thick insulation (250mm+), using multiple layers or alternative materials might be more practical.

Foil facings melt under heat: Standard PIR with aluminium foil facings isn’t suitable beneath torch-applied roofing felt – the torch heat melts foil. Specialist glass tissue faced boards (Celotex Crown-Fix, Kingspan TR26, equivalents) are required for torch-applied systems.

Can’t be recycled easily: PIR offcuts and waste can’t be recycled in most areas. All waste typically goes to landfill. Minimizing waste through careful cutting planning matters for environmental and cost reasons.

Working with PIR: Trade Guidance

Practical guidance for trade professionals installing PIR insulation.

Cutting PIR Boards

Tools: Cut PIR boards using a fine-toothed saw (standard wood saw works) or a sharp knife. For knife cutting, score deeply through the facing and into the foam, then snap the board over a straight edge.

Technique: Measure carefully before cutting. For friction-fit applications (between rafters or joists), cut boards 5-10mm oversized – the compression creates tight fit preventing air gaps. For applications where boards butt together, cut accurately to size for tight joints.

Dust and mess: PIR creates minimal dust and mess when cutting compared to EPS or phenolic. Standard site cleanup handles any debris easily.

Handling and Storage

Manual handling: Standard PIR boards (2400x1200mm) are manageable for one person. A 100mm board weighs approximately 9-10kg. Thicker boards (150mm) become awkward for one person but still manageable with care.

Storage: Store boards flat in their packaging until needed. Stack maximum 10 boards high to prevent bottom boards compressing. Keep boards dry and protected from direct sunlight – UV exposure degrades foil facings over weeks of exposure.

Weather protection: While PIR resists moisture, protect boards from rain and weather during storage. Wet facings prevent proper tape adhesion during installation. Keep boards under cover or tarpaulins when not actively working with them.

Joint Treatment

Taping joints: Seal all board joints with aluminium foil tape to prevent air infiltration. Air movement through untaped joints reduces thermal performance by 20-30%.

Apply tape to clean, dry board surfaces. Press firmly for good adhesion. Overlap tape ends by 50mm minimum where tape joints meet.

When to tape: For floors, walls, and roofs where achieving designed airtightness matters, tape all joints. Some installers skip taping on floors beneath screed, reasoning that screed seals joints. This is poor practice – taping costs little and provides significant airtightness benefit.

Fixing Methods

Floors: Loose-laid with screed weight holding boards in place. No mechanical fixings needed.

Walls (cavity): Cavity wall ties designed for use with insulation. Ensure ties don’t create thermal bridges through inadequate design or installation.

Walls (internal): Mechanical fixings or adhesive dabs. For adhesive dab method, apply dabs to board backs per system specification (typically 5-9 dabs per board depending on size).

Roofs (above deck): Mechanical fixings through boards into deck. Follow manufacturer specifications for fixing density based on wind uplift calculations. More fixings than necessary creates thermal bridging, but too few risks wind damage.

Roofs (between rafters): Friction fit with no fixings needed. The compression between rafters holds boards in position.

Common Installation Mistakes

Using wall-grade PIR for floors: Wall-grade boards (100 kPa) compress under floor loading. Always verify minimum 120 kPa compressive strength for beneath-screed applications.

Not taping joints: Untaped joints allow air infiltration reducing thermal performance significantly. Take time to tape – it’s quick and provides meaningful benefit.

Compressing boards into undersized spaces: Forcing boards into spaces that are too small compresses the foam, reducing thickness and thermal performance. Cut accurately to fit properly without force.

Leaving boards exposed to weather: While PIR resists moisture, protect boards from rain during installation. Wet facings prevent tape adhesion and create installation complications.

Inadequate edge sealing: Gaps between boards and perimeter walls at floor edges create thermal bridging and air infiltration paths. Ensure tight fits at all edges.

PIR Insulation Product Options

Understanding PIR product options helps specification and procurement.

Major UK Manufacturers

Celotex (Saint-Gobain): Most widely recognized brand. GA4000 series is the general application range covering most uses. Specialist ranges include TB4000 (thin boards), XR4000 (roofs), FL4000 (enhanced-strength floors), Crown-Fix (glass tissue faced).

Kingspan: Largest manufacturer globally with extensive product range. Therma series is standard PIR. TR27 for general application, TR26 for torch-applied systems, TF70 for floors. Kooltherm range is premium modified chemistry achieving 0.018-0.020 W/mK.

Recticel: Produces Eurethane and Powerroof branded PIR. Good quality at competitive pricing. Lower brand recognition than Celotex/Kingspan but functionally equivalent.

Ecotherm: Positions as environmentally-focused manufacturer. Eco-Versal general application range. Products meet same standards as other manufacturers.

IKO Enertherm: Produces PIR alongside roofing materials. Good option when sourcing insulation and waterproofing together for flat roofs.

Selecting Between Brands

For most applications, brand selection makes minimal difference. All major manufacturers produce PIR meeting BS EN 13165 with equivalent specifications.

Practical selection factors:

• What your regular merchant stocks
• Pricing for required quantities
• Delivery lead times
• Technical support if needed for complex applications

Don’t overthink brand selection for standard applications. Any major brand at correct thickness and compressive strength performs identically.

Product Codes and Naming

Different manufacturers use different naming conventions:

Celotex: GA4000 (General Application), TB4000 (Thin Board), numbers indicate series Kingspan: TR/TF/TW + numbers (TR=Therma roof, TF=Therma floor, TW=Therma wall) Others: Various naming systems

When ordering, specify:

• Thickness required
• Compressive strength needed (for floors specify minimum 120 kPa)
• Facing type if specialist facing required (glass tissue for torch-applied felt)
• Quantity

Clear specification prevents confusion from different manufacturer naming systems.

Thickness Availability

Common stocked thicknesses: 50mm, 75mm, 100mm, 120mm, 150mm

These cover most applications. Less common thicknesses (like 90mm, 110mm, 130mm) may require special order with longer lead times.

For PIR thickness selection, calculate required thickness for target U-value, then specify the nearest commonly-available thickness meeting or exceeding requirements.

Quality Standards

All reputable PIR products should:

• Meet BS EN 13165 (European standard for PIR/PUR insulation)
• Carry CE marking demonstrating Construction Products Regulation compliance
• Provide Declaration of Performance specifying thermal conductivity, compressive strength, fire rating, and other key characteristics
• Come from manufacturers with quality control systems ensuring consistent product specifications

Verify products meet these standards when sourcing, particularly from lesser-known suppliers or import sources.Looking for PIR insulation for your project? Online Insulation stocks the complete range of PIR boards from all major manufacturers in thicknesses from 25mm to 200mm, with expert technical advice and fast UK delivery for trade professionals.