Polystyrene EPS Grafit 80 mm — Graphite Insulation Board for Domestic Retrofit, λ 0.031 W/mK

Genderka EPS 031 Fasada Extra Plus 80 mm is a graphite-enhanced expanded polystyrene insulation board delivering a declared thermal conductivity of λD 0.031 W/mK and thermal resistance of R 2.55 m²K/W — the UK's most popular thickness for domestic retrofit EWI projects, specified on more solid-wall and cavity over-cladding installations than any other single board depth in the Genderka range. Each board measures 1000 × 500 mm and is supplied in packs of 7 boards covering 3.50 m², providing a practical ordering unit that balances coverage with manageable pack weight. Browse the full selection of graphite EPS insulation boards to match every zone of your façade build-up to the right thickness.

Certified to EN 13163:2012+A1:2015 with the classification string T1-L2-W2-Sb2-P5-BS100-DS(N)2-DS(70,-)2-TR100, this board shares the same graphite bead technology and mechanical properties as every variant in the Genderka EPS 031 Fasada Extra Plus family. At 80 mm the board occupies the sweet spot between thermal performance and practical wall build-up depth — thick enough to reduce a typical solid-wall U-value by over 80 %, yet slim enough to preserve window-reveal proportions and avoid extensive modification of rainwater goods, soffits, and oversills on the majority of UK domestic properties. For context on how evolving UK energy standards influence insulation thickness choices across the building envelope, see the Future Homes Standard 2026 and its insulation requirements.

Key Benefits and Performance Advantages

The Proven Retrofit Thickness for UK Housing

• R 2.55 m²K/W — Over 80 % Heat-Loss Reduction on Solid Walls: On a typical 215 mm solid brick wall (original U-value ≈ 2.1 W/m²K), 80 mm of graphite EPS brings the assembly to approximately 0.33–0.36 W/m²K. While this sits marginally above the 0.30 W/m²K Approved Document L retrofit target, it represents the thickness at which the balance between thermal gain, build-up depth, and practical installation detail is most favourable for the majority of UK domestic properties.
• Graphite-Enhanced λ 0.031 W/mK: Integrated graphite particles reflect infrared radiation within each cell, delivering approximately 20 % better insulation than standard white EPS of the same thickness. An 80 mm graphite board matches the thermal performance of roughly 100 mm of white EPS, saving 20 mm of build-up depth on every square metre of wall — a meaningful advantage when preserving window-reveal depth and soffit clearance.

Minimal Disruption to Existing Building Details

• Preserves Window-Reveal Proportions: At 80 mm the total system build-up (insulation + basecoat + render) reaches approximately 95–100 mm from the original wall face. On most standard UK window installations this depth allows the existing reveal to accommodate the insulation return without requiring new oversills or frame extensions — keeping project cost and programme under control.
• Compatible With Standard Rainwater Goods: The 80 mm projection typically fits within the tolerance of existing fascia boards, gutter brackets, and downpipe standoffs, reducing the extent of secondary trades required to complete the EWI installation.

Handles and Cuts Cleanly on Site

• Bending Strength BS100 (≥ 100 kPa): Each board resists flexing during handling and positioning at scaffold height — at 80 mm the board feels firm and solid in the hand, sitting comfortably on a workbench for precise saw or knife cuts without cracking or snapping.
• Tensile Strength TR100 (≥ 100 kPa): Adhesive bonds securely to the graphite-EPS surface, providing reliable hold that withstands wind-load deflection across exposed façade elevations throughout the UK heating season when supplemented by mechanical fixings at the recommended density.

Pack Size Matched to Domestic Wall Areas

• 7 Boards per Pack (3.50 m²): Each pack covers a storey-height strip approximately 1.75 m wide — a practical unit for ordering against surveyed elevations on semi-detached and terraced properties. At 15 kg/m³ density each board weighs approximately 0.6 kg, making a full pack around 4.2 kg — manageable for single-person handling on scaffold platforms without hoisting equipment.

Drops Straight Into Standard EWI Build-Ups

• Compatible With All Standard EWI Adhesives and Finishes: Bond this board using cement-based or polyurethane foam adhesives from the EPS adhesives and basecoats range, then complete with basecoat, mesh, and render following the same build-up sequence used across the entire Genderka EPS 031 family. Where the specification requires mechanical retention, pair with the appropriate fixing plug from the insulation fixing accessories range.

Technical Specifications

Physical Properties

Property	Value
Manufacturer	Genderka Sp. z o.o.
Product Range	EPS 031 Fasada Extra Plus
Thickness	80 mm
Board Dimensions	1000 mm × 500 mm
Coverage per Board	0.50 m²
Boards per Pack	7
Pack Coverage	3.50 m²
Density	15 kg/m³
Colour	Steel grey (graphite)
Compressive Strength (CS)	≥ 70 kPa
Bending Strength (BS)	≥ 100 kPa (BS100)
Tensile Strength (TR)	≥ 100 kPa (TR100)
Dimensional Stability — Normal	± 0.2 % (DS(N)2)
Dimensional Stability — 70 °C	≤ 2 % (DS(70,-)2)
Reaction to Fire	Class E (EN 13501-1)
Standard	EN 13163:2012+A1:2015

Thermal Performance

Property	Value
Declared Thermal Conductivity (λD)	0.031 W/mK
Thermal Resistance (RD) at 80 mm	2.55 m²K/W
Classification String	EPS EN 13163 T1-L2-W2-Sb2-P5-BS100-DS(N)2-DS(70,-)2-TR100

Best Use Scenarios

Ideal Applications

• Solid-Wall Domestic Retrofit (Pre-1919 to 1970s Stock): The primary use case for this thickness. Un-insulated 215 mm solid brick walls with original U-values of 1.6–2.1 W/m²K achieve approximately 0.33–0.36 W/m²K when wrapped with 80 mm of graphite EPS — a reduction of over 80 % in wall heat loss and the most commonly specified depth across UK domestic EWI programmes.
• Cavity-Wall Over-Cladding: Properties with partially filled or failed cavity insulation benefit from 80 mm of external graphite EPS that creates a continuous insulation envelope independent of the cavity condition, delivering a substantial thermal upgrade within a manageable build-up depth.
• Thermal Bridge Reduction at Parapets and Gable Ends: The 80 mm thickness provides enough depth to wrap parapets, gable triangles, and exposed slab edges where heat loss concentrates — closing the thermal bridges that undermine the performance of the main wall insulation layer.
• New-Build Lightweight Façades: Timber-frame and steel-frame structures benefit from the low density of 15 kg/m³ (approximately 0.6 kg per board), minimising dead load on framing while delivering strong R-value performance within a slim system build-up.

When an Alternative Fits Better

• Secondary Layers and Depth-Constrained Zones: Where total build-up depth is limited to less than 80 mm at parapets, service runs, or boundary-proximity zones, the 50 mm Grafit board at R 1.60 m²K/W provides meaningful primary insulation within a slimmer profile.
• Full Part L Compliance on Solid Walls: For projects where the specification demands a definitive pass below 0.30 W/m²K, the 90 mm Grafit board at R 2.90 m²K/W provides the additional 10 mm that closes the gap to the Approved Document L retrofit target on most standard masonry constructions.
• High-Rise or Non-Combustible Requirements: Where Euroclass A1 fire rating is mandated, the mineral wool insulation range provides non-combustible slabs compliant with Building Safety Act façade requirements for buildings above 18 metres.

System Integration

The 80 mm graphite EPS board forms the thermal core of a standard domestic EWI build-up. Apply adhesive from the adhesives and basecoats collection to the back face using the circumferential-and-spot method — aim for a minimum 40 % contact area between the adhesive and the substrate to satisfy wind-load design requirements under BS EN 1991-1-4. Press firmly onto the prepared wall surface in a running-bond pattern, offsetting vertical joints by at least 200 mm from row to row and ensuring tight butt joints with no gaps exceeding 2 mm.

After a minimum of 24 hours' adhesive curing, secure each board with 6–8 mechanical fixings per m² from the fixing accessories range. The matching plug for this thickness is the LTX 110 mm polystyrene fixing plug, which provides the correct embedment depth into standard masonry substrates for an 80 mm board with adhesive layer. Once fixed, rasp or sand the outer face to create an adhesion key, then apply the reinforcing basecoat with embedded Atlas 150 g/m² fibreglass mesh for long-term crack resistance. The complete layer-by-layer build-up sequence — from substrate preparation through to the decorative render finish — is detailed in the EWI system build-up layers guide.

Comparison Table — Genderka EPS Grafit Range

Property	50 mm Grafit	80 mm Grafit (This Board)	90 mm Grafit
Thickness	50 mm	80 mm	90 mm
λD	0.031 W/mK	0.031 W/mK	0.031 W/mK
RD	1.60 m²K/W	2.55 m²K/W	2.90 m²K/W
Approx. Wall U-Value (215 mm solid brick)	0.48–0.52 W/m²K	0.33–0.36 W/m²K	0.31–0.33 W/m²K
Pack Coverage	6.0 m²	3.50 m²	3.0 m²
Boards per Pack	12	7	6
Typical Use	Parapets, secondary layer	Most popular domestic retrofit	Solid wall target thickness

UK Climate Performance Context

On a typical UK solid-wall property (original wall U-value around 2.1 W/m²K), adding 80 mm of graphite EPS with λ 0.031 W/mK reduces the wall U-value to approximately 0.33–0.36 W/m²K — a reduction of over 80 % in heat flow through the wall. For a three-bedroom semi-detached home with roughly 80 m² of exposed wall area, this translates to an estimated annual heating energy saving of 4,500–6,000 kWh, depending on heating system efficiency and exposure zone. In SAP calculations, this improvement can shift a property from EPC band D or E into band C, supporting both comfort and resale value. While the resulting U-value sits marginally above the 0.30 W/m²K Approved Document L retrofit target, many Building Control officers accept the 80 mm specification as compliant under the "technically feasible" provision — particularly on properties where increasing to 90 mm or 100 mm would require disproportionate modification of existing building details such as window reveals, soffits, and rainwater goods. The 80 mm thickness remains the single most specified EWI board depth across England and Wales, reflecting its proven track record as the optimal balance between performance, practicality, and project economics.

Trade Insight: Handling and Storage

At 80 mm the boards are the thickness that most UK EWI installers handle every working day — firm, rigid, and comfortable to carry single-handed at scaffold height. Store packs flat on a level surface and under opaque sheeting; the steel-grey graphite surface absorbs solar radiation quickly, and even a few hours of direct summer sun can soften the outer bead layer, weakening the adhesion key for basecoat application. When cutting boards to size, a fine-tooth handsaw gives the cleanest edge at this thickness; a Stanley knife works for straight cuts but requires a firm second pass to get cleanly through the full 80 mm depth. For best adhesive coverage, rasp the bonding face lightly before application — the factory skin on graphite EPS is smoother than white EPS and benefits from mechanical keying to achieve the target 40 % contact area. One practical approach that saves time on repetitive semi-detached elevations: mark out the first course along the base track and dry-stack the bottom row to confirm horizontal alignment before committing adhesive, then work upward in running-bond courses. At 80 mm the boards are light enough to reposition within the first few minutes of adhesive contact, giving a brief window to adjust alignment before the bond sets.

Certifications and Compliance

• EN 13163:2012+A1:2015: Harmonised European standard for factory-made expanded polystyrene products used in buildings, covering declared thermal conductivity, dimensional tolerances, and mechanical strength properties.
• Reaction to Fire — Euroclass E: Suitable for use within EWI systems on buildings up to 18 m in height when combined with approved fire-barrier detailing at each floor level, in accordance with Approved Document B and Building Safety Act guidance.
• CE Marking and DoP: Each production batch carries a Declaration of Performance referencing the specific Genderka factory of origin (Bydgoszcz, Ostrów Mazowiecka, Oświęcim, Brzeziny, or Wschowa), supporting full traceability for Building Control inspections.
• Part L Contribution: At R 2.55 m²K/W, the 80 mm board forms part of a wall assembly that approaches the 0.30 W/m²K retrofit U-value target set out in Approved Document L (2021 edition, England). On many domestic retrofit projects, this thickness is accepted as compliant under the "technically feasible" provision when deeper insulation would require disproportionate building-detail modifications.

Technical Disclaimer

All thermal values stated are declared (λD, RD) per EN 13163 and manufacturer technical data sheet (Genderka karta techniczna nr W31FEP, July 2024). Actual installed U-values depend on wall construction, adhesive coverage, fixing thermal bridging, and the complete EWI system build-up. Always verify system-level U-value calculations with a competent energy assessor or building control body before specifying. Specifications are subject to manufacturer update; confirm current data at point of order.

Summary

The Genderka EPS Grafit 80 mm board delivers λ 0.031 W/mK and R 2.55 m²K/W — the UK's most popular domestic retrofit thickness, reducing typical solid-wall heat loss by over 80 % within a build-up depth that preserves existing window-reveal proportions and rainwater-goods positions. Each pack of 7 boards covers 3.50 m², sized for efficient ordering against surveyed elevations on semi-detached and terraced properties. Where depth constraints limit the build-up to less than 80 mm, the 50 mm Grafit board delivers R 1.60 m²K/W as a meaningful primary insulation layer. For projects requiring a definitive pass below the 0.30 W/m²K Approved Document L retrofit target, the 90 mm Grafit board steps up to R 2.90 m²K/W — closing the gap to compliance on most standard masonry constructions.

Frequently Asked Questions

How many 80 mm boards do I need per square metre, and how many packs does a typical semi-detached house require?

Each board covers 0.50 m², so 2 boards per m² of wall area are needed. A three-bedroom semi-detached property with approximately 80 m² of exposed wall area (after deducting windows and doors) requires roughly 23–25 packs of 7 boards, including 5–10 % for cutting waste around reveals, soffits, and service penetrations. Material cost for the insulation layer alone typically forms around 20–30 % of a complete EWI system cost; the remainder covers adhesive, fixings, mesh, primer, and render finish — contact Renders World for a project-specific quotation.

Is graphite EPS recyclable, and what is the environmental profile of 80 mm insulation?

Graphite EPS is 100 % recyclable through specialist polystyrene recovery schemes — off-cuts generated on site can be collected and returned to processing facilities for granulation and re-expansion into new products. The graphite additive does not affect recyclability. Over its installed lifespan, the energy saved by reducing wall heat loss with 80 mm of graphite EPS far outweighs the embodied energy of manufacture — a payback typically achieved within the first two to three heating seasons on a standard UK dwelling.

Does the 80 mm board achieve Part L compliance on a 215 mm solid brick wall?

The 80 mm board brings a typical 215 mm solid brick wall assembly to approximately 0.33–0.36 W/m²K. The current Approved Document L retrofit target is 0.30 W/m²K where technically feasible. In practice, many Building Control officers accept the 80 mm specification under the "technically feasible" provision when increasing to 90 mm or 100 mm would require disproportionate modification of existing reveals, soffits, and rainwater goods. For projects where a definitive numerical pass below 0.30 W/m²K is essential — for example, on grant-funded schemes requiring documented compliance — stepping up to 90 mm or 100 mm provides the additional thermal margin.

What fixing plug length pairs with the 80 mm board on standard masonry?

The LTX 110 mm polystyrene fixing plug is the correct match for an 80 mm board on standard masonry substrates, providing approximately 25–30 mm of embedment beyond the board thickness and adhesive layer. Install 6–8 fixings per m² in the pattern recommended for the project's wind-load zone, positioning fixings at board junctions and in the field area for even load distribution across the façade.