Single Skin Metal Roofing & Wall Cladding Systems

The most commonly specified insulation for double skin metal roofing and wall systems is glass wool or mineral wool (rock wool) in blanket or roll format available in densities from 10 kg/m³ for standard industrial applications up to 32 kg/m³ or higher for demanding acoustic applications. Insulation thickness is selected to achieve the target U-value for the building: standard industrial specifications typically use 100–150mm to achieve U-values in the 0.25–0.45 W/m²K range; higher thermal performance specifications for temperature-controlled or low-energy buildings may require 150–200mm or more. Rigid insulation board is also available for specific applications. Our specification team will confirm the correct insulation type, density, and thickness for your thermal and acoustic targets.

The liner rail is a secondary support system typically a Z-purlin, hat section, or proprietary liner rail profile that spans between the primary purlins or girts and supports the inner liner panel below the insulation layer. The liner rail holds the liner panel at the correct depth below the outer sheet to accommodate the specified insulation thickness, maintains the liner panel's alignment and fixing positions, and provides the structural connection for the liner panel fixing. Correct liner rail specification and installation is essential to achieving the designed insulation thickness without compression (which reduces thermal performance) and to maintaining the liner panel's flat, consistent interior appearance.

The U-value (thermal transmittance) of a double skin build-up depends on the insulation type, density, and thickness, the thermal bridging through the liner rail and fixing system, and the inner and outer surface resistances. As a planning reference: 100mm glass wool at standard density typically achieves a U-value of approximately 0.35–0.40 W/m²K; 150mm glass wool achieves approximately 0.22–0.28 W/m²K; 200mm achieves approximately 0.18–0.22 W/m²K subject to liner rail bridging correction factors. The structural engineer or building services consultant confirms the required U-value for the project's regulatory compliance and energy performance target, and the insulation specification is selected accordingly.

Yes double skin systems can be retrofitted to existing single-skin metal buildings as a performance upgrade. The standard retrofit approach installs a liner rail system to the existing purlins, positions the insulation between the liner rails, and fixes the inner liner panel to create the completed double skin build-up beneath the existing outer sheet. This approach adds thermal, acoustic, and condensation control performance to an existing building without replacing the outer cladding at significantly lower cost and programme impact than full re-cladding. Where the existing outer sheet is also being replaced, a complete new double skin system can be installed simultaneously, achieving the full performance specification in a single operation.