Insulation Board Types: A Selection Guide for UK Trade Professionals

Rigid insulation boards include PIR (polyisocyanurate), EPS (expanded polystyrene), XPS (extruded polystyrene), and phenolic foam, each with distinct thermal conductivity, compressive strength, and moisture resistance characteristics affecting suitability for different applications. PIR boards achieve the best thermal performance per millimetre (0.022 W/mK) making them the standard choice for space-constrained applications, while EPS offers lower cost for applications where thickness isn’t constrained, XPS provides enhanced moisture resistance for ground-contact applications, and phenolic delivers premium performance (0.018-0.020 W/mK) for ultra-thin build-ups. Understanding each board type’s characteristics helps trade professionals specify appropriate products for walls, roofs, floors, and specialist applications across UK construction projects.

Understanding Rigid Insulation Boards

Rigid insulation boards differ from fibrous insulation (mineral wool, glass wool) in structure and properties. Rigid boards are solid foam materials you can walk on, cut with standard tools, and install without support structures in many applications.

What Makes Boards “Rigid”

Rigid insulation consists of solid foam with structural integrity. The boards maintain their shape and thickness under normal handling without external support. This rigidity comes from the foam structure – millions of tiny cells (either open or closed) creating a solid material.

Compare this to fibrous insulation which is flexible, compressible, and needs support (between studs or joists) to maintain position. Boards can be loose-laid on floors, mechanically fixed to walls, or installed above roof decks without additional support beyond fixings.

Key Properties That Differ Between Board Types

Thermal conductivity (lambda value): How readily heat passes through the material. Lower values mean better insulation. Lambda values range from 0.018 W/mK (premium phenolic) to 0.038 W/mK (basic EPS).

Compressive strength: How much loading the board can carry before compressing. Critical for floor applications. Measured in kPa (kilopascals). Ranges from 70 kPa (basic EPS) to 200+ kPa (enhanced PIR or XPS).

Moisture resistance: How the board performs in damp conditions. Closed-cell foams (PIR, XPS, phenolic) resist moisture well. Open-cell or expanded foams (EPS) absorb moisture more readily though still perform adequately in most above-ground applications.

Fire performance: Reaction to fire varies by material. Most boards achieve Class E or better, adequate for normal use. Some applications require specific fire ratings.

Cost: Price per square metre varies significantly between board types, from budget EPS to premium phenolic.

Common Board Types in UK Construction

PIR (Polyisocyanurate): The most widely used rigid insulation in UK residential construction. Excellent thermal performance, good compressive strength, moisture resistant. Standard choice for walls, roofs, and floors.

EPS (Expanded Polystyrene): Lower-cost option with moderate thermal performance. Suitable for applications where thickness isn’t constrained. Common in commercial construction and ground works.

XPS (Extruded Polystyrene): Enhanced moisture resistance makes XPS suitable for below-ground applications. Higher cost than EPS but better performance.

Phenolic: Premium performance in minimal thickness. Expensive but useful where space constraints are severe.

Polyurethane (PUR): Similar to PIR with slightly different chemistry. Less common in UK than PIR but functionally similar.

The sections below detail each board type’s characteristics, applications, and when to specify them.

PIR Insulation Boards: High-Performance Option

PIR (polyisocyanurate) insulation boards dominate UK residential construction due to excellent thermal performance in manageable thicknesses.

What PIR Insulation Is

PIR boards consist of rigid closed-cell foam created through chemical reaction between polyisocyanurate and other compounds. The manufacturing process produces boards with:

• Closed-cell structure (95%+ of cells are sealed)
• Low-density foam (30-35 kg/m³ typical)
• Rigid structural integrity
• Aluminium foil or glass tissue facings bonded to both sides

The closed cells trap low-conductivity gas improving thermal performance. Over time, some gas diffuses out and air diffuses in, but declared lambda values account for this aging effect.

Technical Specifications

Thermal conductivity: 0.022-0.023 W/mK (most products declare 0.022 W/mK)

Compressive strength:

• Wall/roof grade: 100-120 kPa
• Floor grade: 120-150 kPa
• Enhanced strength: 150-200 kPa

Density: 30-35 kg/m³

Fire rating: Class E typically (per BS EN 13501-1)

Moisture resistance: Very good – closed-cell structure resists water absorption

Available thicknesses: 25mm-200mm depending on manufacturer

Board sizes: 2400x1200mm standard (2.88m² per board)

PIR Performance Advantages

Best thermal performance per thickness: PIR’s 0.022 W/mK lambda outperforms EPS (0.031-0.038 W/mK) and mineral wool (0.035-0.044 W/mK) significantly. This means less thickness needed for equivalent thermal performance.

For achieving 0.18 W/m²K in a floor:

• PIR needs approximately 100mm
• EPS needs approximately 140-160mm
• Mineral wool needs approximately 150-180mm

Adequate compressive strength: Floor-grade PIR (120 kPa minimum) handles residential and light commercial floor loading without compression. The boards maintain thickness and performance under screed and floor finishes.

Moisture resistance: The closed-cell structure prevents water penetration. PIR maintains thermal performance even if temporarily exposed to rain during installation (though you should protect it). This contrasts with fibrous insulation which saturates if it gets wet.

Dimensional stability: PIR boards maintain size and shape across temperature variations. Summer heat or winter cold doesn’t cause significant expansion/contraction creating gaps between boards.

Workability: PIR cuts cleanly with hand tools (fine-toothed saw or sharp knife). Installation is straightforward – boards fit between studs, lay on floors, or fix to walls without specialist equipment or training.

PIR Applications

PIR suits virtually every insulated building element:

Solid floors: 100mm PIR above concrete slab beneath screed achieves Part L compliance (0.18 W/m²K) for ground floors

Suspended floors: Between joists, above joists, or below joists depending on construction

Cavity walls: 75-100mm in partial fill cavity walls achieves 0.16-0.22 W/m²K

Internal wall insulation: 75-100mm provides good thermal performance without excessive internal space loss

Pitched roofs: Between rafters, above rafters, or combination approaches

Flat roofs: 120-140mm in warm roof construction achieves 0.16 W/m²K requirement

PIR Limitations

Cost: PIR costs more per square metre than EPS. For applications where thicker insulation is acceptable, EPS might provide better value.

Fire performance in high-rise: Buildings over 18m face additional scrutiny on combustible materials following post-Grenfell regulations. PIR is combustible (Class E) which complicates use in some high-rise external wall build-ups.

Performance at very high temperatures: PIR’s upper continuous temperature limit is approximately +80°C. For applications requiring higher temperature resistance (some industrial applications), alternative materials might be needed.

PIR vs Alternatives Decision Framework

Choose PIR when:

• Space/thickness is constrained
• You need good thermal performance in minimal build-up depth
• Application involves loading (floors requiring compressive strength)
• Moisture exposure is possible
• Working with standard UK residential construction

Consider alternatives when:

• Thickness isn’t constrained and lower-cost options suit
• Below-ground application requires maximum moisture resistance (XPS might be better)
• Ultra-thin build-up justifies premium pricing (phenolic performs better)
• Fire performance requirements exclude combustible materials (mineral wool required)

EPS Insulation Boards: Expanded Polystyrene

EPS (expanded polystyrene) is familiar to most people as white foam packaging material. Construction-grade EPS boards are denser and more rigid than packaging foam but share the basic expanded bead structure.

What EPS Insulation Is

EPS forms by expanding polystyrene beads with steam, then moulding expanded beads into rigid boards. The manufacturing process creates boards with:

• Visible bead structure (you can see individual expanded beads)
• Lightweight material (15-30 kg/m³ typical)
• Open structure (air circulates between beads more readily than closed-cell foams)
• White or grey color (graphite-enhanced EPS is grey)

Unlike PIR’s closed-cell structure, EPS has more interconnected voids between expanded beads. This makes EPS slightly more permeable to air and moisture compared to closed-cell alternatives.

Technical Specifications

Thermal conductivity:

• Standard white EPS: 0.035-0.038 W/mK
• Enhanced (graphite) grey EPS: 0.031-0.033 W/mK

Compressive strength: 70-250 kPa depending on grade

• Standard grade: 70-100 kPa
• Enhanced grade: 100-150 kPa
• High-strength grade: 200-250 kPa

Density: 15-30 kg/m³ (lighter than PIR)

Fire rating: Class E typically

Moisture resistance: Moderate – absorbs some moisture but performs adequately in most applications

Available thicknesses: 25mm-500mm (much thicker boards available than PIR)

Board sizes: Various, commonly 2400x1200mm, 1200x1000mm, or custom sizes

EPS Performance Characteristics

Lower cost: EPS typically costs 40-60% less per square metre than PIR. For projects where material cost matters and thickness isn’t constrained, EPS provides good value.

Thicker boards available: EPS manufactures economically in very thick boards (300mm+). Where thick insulation is needed (highly insulated buildings, cold stores), EPS provides more cost-effective thickness than PIR.

Lightweight: Lower density than PIR makes EPS easier to handle for very large boards. A 300mm EPS board weighs less than 150mm PIR, easing manual handling.

Workability: EPS cuts easily with hot wire cutters (specialized tool) or saws. However, cutting EPS with saws creates significant mess – thousands of small foam beads spread everywhere. Hot wire cutting is cleaner but requires specialist equipment.

EPS Limitations

Poorer thermal performance: 0.035-0.038 W/mK for standard EPS means approximately 60-70% more thickness than PIR for equivalent thermal resistance. Where space is limited, this rules out EPS.

For 0.18 W/m²K floor:

• PIR needs 100mm
• Standard EPS needs 160mm
• Enhanced EPS needs 140mm

Lower compressive strength (standard grades): Standard EPS at 70-100 kPa has inadequate compressive strength for many floor applications beneath screed. Enhanced or high-density grades achieve adequate strength but cost more, eroding EPS’s price advantage.

Moisture sensitivity: EPS absorbs more moisture than PIR or XPS. For below-ground applications or situations with sustained moisture exposure, XPS or PIR performs better.

EPS Applications

EPS suits specific applications where its characteristics provide advantages:

Foundations and ground works: EPS beneath foundation slabs provides insulation and void forming. Thicker boards are economical, and below-slab positioning protects EPS from moisture. Common in commercial and industrial buildings.

External wall insulation (EWI) systems: Many EWI systems use EPS boards beneath render. The thickness isn’t constrained like internal insulation, and render protects EPS from weather and UV.

Floors where thickness isn’t limited: Commercial buildings with high floor-to-floor heights can accommodate thicker insulation without constraint. EPS provides adequate performance at lower cost than PIR.

Inverted roofs: Some inverted roof systems use XPS, but high-density EPS also works. The ballast (gravel or paving) protects EPS from weather.

Non-habitable buildings: Warehouses, agricultural buildings, or other structures where meeting residential Part L requirements isn’t necessary might use EPS achieving lower U-values at reduced cost.

When to Choose EPS Over PIR

Consider EPS when:

• Build-up depth allows 50-60% more thickness than PIR would need
• Project budget is tight and thickness constraint doesn’t exist
• Below-slab foundation insulation where thick insulation is cost-effective
• Commercial project with relaxed U-value requirements

Stick with PIR when:

• Space is limited
• Standard residential construction meeting Part L requirements
• Floor application requiring reliable compressive strength
• Installation timeline matters (PIR installs faster due to fewer boards for same R-value)

XPS Insulation Boards: Extruded Polystyrene

XPS (extruded polystyrene) is manufactured differently from EPS, creating boards with enhanced properties particularly moisture resistance.

What XPS Insulation Is

XPS forms by extruding molten polystyrene through dies, creating boards with:

• Uniform closed-cell structure (unlike EPS’s bead structure)
• Smooth surface finish (no visible beads)
• Distinctive color coding by manufacturer (pink, blue, green, yellow)
• Higher density than EPS (28-45 kg/m³)

The extrusion process creates smaller, more uniform cells completely closed, giving XPS better moisture resistance than EPS.

Technical Specifications

Thermal conductivity: 0.029-0.035 W/mK depending on grade

Compressive strength: 200-700 kPa depending on grade

• Standard grade: 200-300 kPa
• High-strength grade: 300-500 kPa
• Heavy-duty grade: 500-700 kPa

Density: 28-45 kg/m³

Fire rating: Class E typically

Moisture resistance: Excellent – virtually impermeable to water and water vapour

Available thicknesses: 20mm-200mm typical

Board sizes: Various, commonly 1250x600mm or 2500x600mm

XPS Performance Characteristics

Superior moisture resistance: XPS’s closed-cell structure provides the best moisture resistance of common insulation boards. Water absorption is negligible even with long-term immersion. This makes XPS the standard choice for below-ground applications.

Very high compressive strength: XPS achieves compressive strengths exceeding PIR or EPS significantly. Heavy-duty grades handle vehicle loading, making XPS suitable for car park decks, loading bays, and industrial floors with heavy equipment.

Dimensional stability: XPS maintains dimensions across temperature and moisture variations better than EPS. Boards don’t warp or distort in damp conditions.

Long service life: The closed-cell structure and moisture resistance mean XPS performance doesn’t degrade over time. Below-ground installations maintain thermal performance indefinitely.

XPS Limitations

Higher cost than PIR: XPS typically costs 20-40% more than equivalent PIR boards. The cost is justified for applications requiring XPS’s specific properties but makes XPS uncompetitive for standard above-ground residential construction.

Moderate thermal performance: Lambda values of 0.029-0.035 W/mK sit between PIR (0.022) and EPS (0.035-0.038). XPS performs better than standard EPS but not as well as PIR, requiring more thickness than PIR for equivalent thermal resistance.

Limited thickness availability: XPS isn’t manufactured in very thick boards like EPS. Maximum practical thickness is approximately 200mm, beyond which you need multiple layers.

XPS Applications

XPS suits applications where moisture resistance and high compressive strength matter:

Below-ground insulation: Insulating basement walls externally, beneath basement floor slabs, or around foundations. XPS handles ground moisture and water table fluctuations without performance degradation.

Inverted roofs: XPS above waterproofing membranes (inverted roof construction). The boards handle roof traffic and weather exposure while protecting membranes from UV and temperature cycling.

Cold stores and refrigerated spaces: Where insulation experiences sustained cold temperatures and potential condensation, XPS’s moisture resistance prevents performance loss.

Car parks and loading bays: High-strength grades handle vehicle loading. XPS beneath concrete slabs in parking structures provides thermal and structural separation.

Ground-contact perimeter insulation: Insulating ground floor edges externally where insulation sits in contact with soil. XPS handles moisture exposure without degradation.

Podium decks and plaza decks: Waterproof deck insulation where boards experience foot traffic, planting, and irrigation. XPS maintains performance in these demanding conditions.

When to Choose XPS

Specify XPS when:

• Below-ground application with direct soil contact
• Sustained moisture exposure is likely
• Very high compressive strength is required (vehicle loading)
• Long service life in harsh conditions justifies premium pricing

Stick with PIR when:

• Standard above-ground residential construction
• Moisture exposure is normal construction weather only
• Standard residential floor loading only
• Cost-effectiveness matters and XPS properties aren’t needed

Phenolic Insulation Boards: Premium Performance

Phenolic foam insulation delivers the best thermal performance per millimetre of any common insulation board, at premium pricing.

What Phenolic Insulation Is

Phenolic boards consist of rigid phenolic foam (created from phenol-formaldehyde reaction) with:

• Very fine closed-cell structure (smaller cells than PIR)
• Low density (35-40 kg/m³)
• Facing materials bonded to surfaces (usually aluminum foil or glass tissue)
• Distinctive appearance (often black or dark brown foam core)

The fine cell structure and trapped gases create excellent thermal performance in thin sections.

Technical Specifications

Thermal conductivity: 0.018-0.020 W/mK (best performance of common boards)

Compressive strength: 100-150 kPa typical

Density: 35-40 kg/m³

Fire rating: Class B or Class C typically (better than PIR, EPS, or XPS)

Moisture resistance: Good (closed-cell structure)

Available thicknesses: 20mm-150mm typical

Board sizes: Usually 2400x1200mm

Phenolic Performance Characteristics

Best thermal performance: Lambda values of 0.018-0.020 W/mK mean phenolic needs approximately 18-20% less thickness than PIR for equivalent thermal performance.

For 0.18 W/m²K floor:

• PIR needs 100mm
• Phenolic needs 80-85mm

This thickness saving matters where every millimetre counts.

Improved fire performance: Class B or C fire rating (compared to Class E for PIR/EPS/XPS) provides better fire performance. This matters for buildings with stringent fire requirements or situations where combustible material content needs minimizing.

Good moisture resistance: Closed-cell structure provides adequate moisture resistance for most applications, similar to PIR.

Phenolic Limitations

High cost: Phenolic typically costs 50-100% more than PIR for equivalent thermal resistance (accounting for thinner boards needed). This premium pricing limits phenolic to applications where the thickness saving justifies extra cost.

Limited availability: Fewer manufacturers produce phenolic boards compared to PIR. Stock availability is more limited, often requiring special order.

Cutting and handling: Phenolic boards create fine dust when cut. Use appropriate dust extraction and PPE. The boards can be brittle, requiring more care during handling and installation than PIR.

Thickness range: Phenolic isn’t manufactured in very thick sections. For applications requiring 150mm+ equivalent thermal resistance, multiple layers or alternative materials may be needed.

Phenolic Applications

Phenolic suits specific applications where ultra-thin insulation justifies premium pricing:

Floor insulation with severe height constraints: Renovations where raising floor level must be minimized. 80mm phenolic provides similar performance to 100mm PIR, saving 20mm of floor height.

Internal wall insulation (space-critical): Historic buildings or small rooms where losing internal space to insulation matters significantly. Using phenolic instead of PIR saves approximately 15-20mm of room width for equivalent thermal performance.

External wall insulation (planning restricted): Where planning restrictions limit how far insulation can project beyond original building line. Thinner phenolic achieves required U-values in restricted build-out depth.

Reveal insulation: Insulating around windows and doors internally where deep reveals aren’t acceptable. Thin phenolic provides thermal break without excessive reveal depth.

Specialist applications: Situations requiring both thin profile and better fire performance than standard PIR.

When to Choose Phenolic

Specify phenolic when:

• Space constraint is severe and every millimetre matters
• Project budget accommodates 50-100% higher insulation cost
• Fire performance requirements favor Class B/C over Class E
• Thickness saving provides tangible benefit (preserves ceiling height, reduces floor level rise, maintains room dimensions)

Stick with PIR when:

• Standard thicknesses fit within available space
• Cost-effectiveness matters
• Standard fire performance (Class E) is adequate
• Reliable availability is important

Comparing Insulation Board Types

Side-by-side comparison helps understanding relative performance across key characteristics:

*Relative cost for equivalent thermal resistance

Thermal Performance Comparison

For achieving 0.18 W/m²K in typical solid floor construction:

This comparison shows phenolic and PIR achieving required performance in significantly less thickness than polystyrene alternatives.

Compressive Strength Comparison

For floor applications beneath screed requiring minimum 120 kPa:

PIR and XPS reliably meet floor loading requirements. EPS requires specifying enhanced grades. Phenolic is borderline for floors.

Moisture Resistance Comparison

Moisture resistance matters for below-ground applications and situations with sustained damp exposure:

Excellent (suitable for below-ground): XPS Very good (suitable for above-ground): PIR, Phenolic
Moderate (protected applications only): EPS

For below-ground applications (basement walls, beneath slabs), XPS is the clear choice. For normal above-ground construction, PIR and phenolic perform adequately. EPS works above-ground but isn’t ideal for situations with prolonged moisture exposure.

Selecting Board Type by Application

Matching board type to application requirements ensures appropriate performance at reasonable cost.

Ground Floors (Solid Concrete)

Primary recommendation: PIR

• 100mm achieves Part L compliance (0.18 W/m²K)
• 120 kPa compressive strength handles residential loading
• Thickness is manageable for standard construction
• Widely available and competitively priced

Alternative: Phenolic (space-constrained renovations only)

• 80-85mm achieves equivalent performance
• Justified only when saving 15-20mm matters significantly
• Premium pricing

Not recommended: EPS or XPS

• EPS needs 140-160mm (excessive thickness for standard floor build-up)
• XPS costs more than PIR without providing advantage for above-ground floors

Ground Floors (Suspended Timber)

Primary recommendation: PIR

• Works between, above, or below joists
• Compressive strength irrelevant (no loading on insulation)
• Good thermal performance in available space

Alternative: EPS (if cost matters and space allows)

• Between-joist installations with deep joists can accommodate thicker EPS
• Cost saving may be worthwhile for large projects

Cavity Walls

Primary recommendation: PIR

• 75-100mm achieves Part L compliance comfortably
• Fits in standard cavity widths with 50mm residual cavity
• Most cost-effective option for typical cavity wall construction

Alternative: Phenolic (planning-restricted developments)

• Where planning limits total wall thickness, thinner phenolic maintains internal space
• Premium pricing justified only when space constraint is severe

Not recommended: EPS or XPS

• EPS would need full-fill installation (complicating drainage) or excessively wide cavities
• XPS provides no advantage over PIR for standard above-ground walls

Internal Wall Insulation

Primary recommendation: PIR

• 75-100mm provides good thermal performance
• Total build-up (insulation + plasterboard + battens) approximately 100-130mm
• Reasonable compromise between performance and space loss

Alternative: Phenolic (small rooms or historic buildings)

• 60-80mm phenolic saves 15-20mm compared to PIR
• Justified where preserving room dimensions matters significantly
• Historic buildings where planning restricts internal alterations may require thinnest practical insulation

Pitched Roofs

Primary recommendation: PIR

• 100-150mm (various configurations) achieves 0.16 W/m²K
• Works between rafters, above rafters, or combination
• Standard choice for residential pitched roofs

Alternatives: None commonly used

• Phenolic offers minimal advantage (roof space constraints are less critical than floor height)
• EPS requires excessive thickness for rafter-depth limitations
• XPS provides no performance advantage over PIR

Flat Roofs

Primary recommendation: PIR

• 120-140mm achieves 0.16 W/m²K for warm roof construction
• Adequate compressive strength for maintenance access
• Moisture resistant for exposure during construction
• Compatible with all major waterproofing systems

Alternative: XPS (inverted roofs only)

• Inverted roof construction places insulation above waterproofing
• XPS’s superior moisture resistance suits above-membrane positioning
• More expensive than PIR but justified for inverted construction benefits

Below-Ground Applications

Primary recommendation: XPS

• Basement wall insulation externally
• Beneath basement floor slabs
• Foundation perimeter insulation
• XPS’s moisture resistance is critical for sustained ground moisture exposure

Alternative: None appropriate

• PIR, phenolic, and EPS all lack adequate moisture resistance for below-ground use
• While PIR resists moisture adequately above ground, below-ground exposure is more severe

Insulation Board Specifications Table

Comprehensive specification comparison for quick reference:

*Phenolic is combustible but achieves better fire rating than other boards

Thickness Required for Common U-Values

Approximate thickness needed to achieve standard Part L requirements in typical constructions:

These figures assume typical constructions. Actual thickness varies with complete build-up details.

Trade Considerations for Board Selection

Beyond technical specifications, practical considerations affect board selection for trade professionals.

Availability and Lead Times

PIR boards stock widely through most merchants in common thicknesses (50mm, 75mm, 100mm, 120mm, 150mm). Order today, collect tomorrow in most areas.

EPS availability is good but varies by region. Some merchants stock basic grades only. Enhanced grey EPS may require ordering.

XPS has medium availability. Major merchants stock it but in limited thickness ranges. Special orders are common for specific thicknesses or high-strength grades.

Phenolic has lowest availability. Usually requires special order with 1-2 week lead times. Not stocked by all merchants.

For project planning, verify material availability before finalizing specifications. Don’t spec phenolic if you need materials in 48 hours and your merchant doesn’t stock it.

Cutting and Installation

PIR: Cuts cleanly with fine-toothed saw or sharp knife. Fast installation. Minimal dust or mess. One person can handle and cut boards easily.

EPS: Cuts with saws (very messy – foam beads everywhere) or hot wire cutters (cleaner but requires specialist tool). Lightweight boards are easy to handle. Installation is quick but site cleanup after cutting takes time.

XPS: Cuts with saws creating some mess but less than EPS. Denser boards require more effort to cut than PIR or EPS. Still manageable with standard hand tools.

Phenolic: Cuts with saws but creates fine dust. Use dust extraction and wear appropriate PPE. Boards can be more brittle than PIR requiring careful handling to avoid damage.

For installation efficiency, PIR provides the best balance of easy cutting, minimal mess, and fast installation.

Waste and Offcuts

PIR and phenolic offcuts have limited reuse potential. Can’t be recycled in most areas. Minimize waste through careful cutting planning.

EPS offcuts can be crushed and recycled in some areas. Check local waste facilities. Volume of EPS waste is higher due to thicker boards needed.

XPS offcuts similar to PIR – limited recycling, aim to minimize waste through planning.

For waste management, all boards require careful cutting planning. Measure twice, cut once actually matters when waste goes to landfill.

Cost Management

For projects where cost matters:

Use PIR as standard: Provides best performance-to-cost ratio for most applications. Widely available competitive pricing.

Consider EPS for limited applications: Ground works, below-slab insulation, or commercial projects with relaxed U-value requirements where thickness isn’t constrained.

Reserve phenolic for situations where thickness saving provides tangible value: Don’t spec phenolic just for marginal performance improvement. The premium pricing needs justifying through genuine space constraints.

Use XPS only where properties are required: Below-ground applications or situations needing very high compressive strength. Don’t spec XPS for standard above-ground residential construction where PIR works fine at lower cost.

Multi-Project Efficiency

Trade professionals working on multiple projects benefit from standardizing on one primary board type (usually PIR) for most applications. This provides:

• Consistent pricing through volume relationships with suppliers
• Simplified ordering and inventory management
• Installation crew familiarity with one product type
• Reduced specification and calculation time

Use alternatives (phenolic, XPS, EPS) only when specific project requirements justify deviation from standard PIR specification.Need insulation boards for your project? Online Insulation stocks the complete range of rigid insulation boards including PIR, EPS, XPS from all major manufacturers, with expert specification advice and fast UK delivery for trade professionals.