External Wall Insulation Boards

An EPS render system uses expanded polystyrene insulation boards alongside compatible fixings, reinforced base coats and external render to improve a building’s thermal performance and provide a durable decorative finish.

Rendit supplies Jablite Grey EPS boards suitable for use with selected K Rend and Parex render systems. Rockwool External Wall Dual Density Slabs are also available for projects requiring a mineral wool insulation solution with enhanced thermal, acoustic and fire-performance properties.

Choosing External Wall Insulation Boards

External wall insulation boards form the thermal layer within an EWI system. They are fixed to the outside of the building and covered using compatible adhesives, mechanical fixings, reinforced base coats and decorative render.

Rendit supplies both grey expanded polystyrene and mineral-wool insulation boards. The most suitable option will depend on the required thermal performance, fire classification, acoustic requirements, substrate and approved render system.

Jablite Grey EPS Insulation Boards

Jablite Grey EPS is a lightweight, closed-cell insulation board suitable for selected reinforced render and cladding systems. The grey colour comes from additives that enhance its insulating performance compared with standard white EPS.

Benefits include:

• Lightweight and straightforward to handle
• Low water absorption
• Available in multiple thicknesses
• Suitable for compatible reinforced render systems
• Compatible with selected K Rend and Sika Parex systems

Jablite Grey EPS boards are currently offered in thicknesses ranging from 20mm to 100mm, with the coverage per pack varying by thickness. 

ROCKWOOL External Wall Dual Density Slabs

ROCKWOOL External Wall Dual Density Slabs are mineral-wool insulation boards developed specifically for external wall insulation systems. Their dual-density construction provides a firmer outer surface for receiving the render system while the inner layer accommodates minor variations in the substrate.

Mineral wool may be selected where a project requires:

• Enhanced fire performance
• Improved acoustic insulation
• Vapour permeability
• Thermal insulation
• Compatibility with an approved mineral-wool EWI system

The product is intended to improve both the thermal and acoustic performance of the building when installed within a correctly specified system.

Selecting the Correct Board Thickness

Insulation thickness should not be selected solely according to the available space or desired appearance. The required thickness will depend on:

• Existing wall construction
• Current and target U-values
• Building regulations
• Thermal bridging
• Exposure and moisture conditions
• Fire-safety requirements
• The approved EWI specification

A U-value calculation or complete system specification may be required before materials are ordered.

Installing External Wall Insulation

Boards should be installed with closely butted, staggered joints and without gaps that could reduce thermal performance. Adhesives, mechanical fixings, base coats, reinforcing mesh, beads and finishing renders must all be compatible with the selected insulation.

EPS and mineral-wool components should not be substituted within an approved system without technical confirmation. Always follow the insulation and render manufacturers’ current installation guidance and obtain a project-specific specification where required.

Browse our EPS and Rockwool insulation boards below, or if you require full written specifications for industry standards compliance please contact us.