External wall insulation (EWI) is one of the most common energy upgrades for homes and buildings in Ireland and the UK. Before you choose a render or a colour, you choose the board. The most common question we hear: graphite EPS vs white EPS – which one is better value?
This guide compares both boards in numbers, shows when each makes sense and explains how to handle grey EPS on site.
What is the difference between grey and white EPS?
Both are expanded polystyrene (EPS) made from fused beads. Graphite EPS (also called grey EPS or enhanced EPS) contains fine graphite particles. These particles reflect and absorb heat radiation inside the board, so less heat passes through. In practice, grey EPS insulates around 20% better than white EPS of the same thickness.
For external walls, both are usually supplied as facade grade boards – often marked EPS 70 – produced to the European standard EN 13163.
Grey EPS vs white EPS in numbers
Typical values – always check the declaration of performance and data sheet of the specific product.
| White EPS (facade) | Grey EPS (facade) | |
|---|---|---|
| Thermal conductivity (λ) | approx. 0.036–0.040 W/mK | approx. 0.030–0.033 W/mK |
| Thickness for a similar thermal resistance | e.g. 150 mm (λ 0.038) | e.g. 125 mm (λ 0.031) |
| Thermal resistance R of that thickness | about 3.9 m²K/W | about 4.0 m²K/W |
| Price per m³ | lower | higher |
| Sensitivity to sun during installation | low | high – needs shading |
Thermal resistance is simply thickness divided by λ. That is why a thinner grey board can do the same job as a thicker white one.
When grey EPS makes sense
- Limited space – window and door reveals, boundaries, narrow side passages, eaves
- Demanding U-values – new builds and deep retrofits that must meet Part L and grant requirements
- Thinner build-up – shorter anchors, smaller reveal returns, less change to roof overhangs and sills
- Total cost – when thinner boards reduce the cost of other parts of the job, the higher price per m³ can pay back
When white EPS is enough
- No limit on wall thickness
- Budget projects where cost per m² is the priority
- Some non-facade uses, such as floors and foundations, where specific EPS grades are used
Handling grey EPS on site: protect it from the sun
Graphite boards absorb solar heat quickly. In direct sun the surface can heat up, the board can deform and joints can open. Good practice:
- Store boards in their packaging, covered and out of direct sun.
- Use scaffold sheeting on sunny elevations during installation.
- Apply the base coat with mesh soon after fixing the boards.
- Follow the system holder's guidance on maximum time before reinforcement.
Boards are only one layer of the system
In Ireland, external wall insulation should be installed as a complete certified system – adhesive, boards, anchors, base coat, mesh, primer and render that were tested together. Swapping one component for a cheaper one can affect certification and warranty. We explain this in NSAI Agrément EWI Systems: Why Buy a Complete System. Fire safety also matters: follow the system certificate for fire barriers and the insulation types allowed on your building.
Transport tip: EPS fills a truck by volume
EPS is light but takes a lot of space. A truck full of boards uses little of its weight capacity. Combining insulation with adhesives and renders in one load uses the trailer better. See Pallet, FTL or Container: Delivery from Poland to Ireland.
How Actitrade helps
Poland is one of Europe's major EPS producers. We supply white and grey EPS facade boards from Polish manufacturers, together with complete EWI system components, and deliver full trucks or mixed loads to your yard or site in Ireland, Northern Ireland and the UK.
FAQ
Is graphite EPS better than white EPS?
For thermal performance, yes – around 20% better at the same thickness. It costs more per m³, so the best choice depends on space limits and the total cost of the job.
What thickness of EPS do I need for external walls?
It depends on the existing wall and the target U-value. Your system designer or certificate holder calculates it for each project. As a rough guide, grey EPS is about 20% thinner than white for the same result.
Why must grey EPS be shaded from the sun?
Graphite absorbs heat. In direct sun the board can expand and warp, which opens joints and can crack the render later.
Can I mix grey and white EPS on one building?
Only if the system certificate allows both boards and the design accounts for different thicknesses. Never mix them randomly on one wall.
What does EPS 70 mean?
It is a strength class: compressive stress of 70 kPa at 10% deformation. EPS 70 is a common grade for external wall insulation.
Read next:
- Winter Building Materials: Cold Weather Adhesives & Renders
- Polish Building Materials Supplier for Ireland & the UK
Planning a facade project?
Send us the wall area and target thickness – we will prepare an offer for both grey and white EPS, with transport. Contact us.