A complete material checklist for an EWI system - insulation boards, render coat, render board, exterior paint and fixings.
External wall insulation is the most effective way to dramatically improve the energy rating of a solid-wall home. Solid walls - common in UK properties built before 1920 - have no cavity to fill, so EWI applied to the outside is the primary route to achieving Part L thermal performance and securing better EPC ratings. Done correctly, it can cut heat loss through the walls by 70% or more.
The EWI system involves multiple layers, each with its own material quantities: insulation board mechanically fixed and adhesive-bonded to the substrate, a reinforcing base coat with glass fibre mesh embedded into it, an optional render carrier board in some specifications, and finally a decorative top coat or silicone render finish. Getting the layer quantities right matters - both for budget control and to ensure the contractor can order materials on programme.
Use Simple mode for a straightforward rectangular building where all four elevations are being treated. Switch to Detailed mode for partial re-renders, semi-detached properties, L-shaped buildings, or where each elevation has a noticeably different number of openings - each wall is entered separately and totalled across all sections.
Work through these 5 calculators in order. Each one uses your net wall area to pre-fill the key inputs - just refine the details and save each result to your project.
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