EPS insulation board or EPS-core sandwich panel: what are you buying?

EPS consists of fused beads of expanded polystyrene. Its documentation gives the thermal conductivity, reaction to fire and properties relevant to its use. For floors, check compressive behaviour. For façades, also check tensile strength perpendicular to the face. A common size of 1,000 × 500 mm is convenient to lay. Board dimensions alone tell you little about the strength or fire performance of the finished element.

A sandwich panel has facings permanently bonded to its core. Wall and roof panels often use sheet-metal facings. The bond allows the panel to carry loads as a composite element. Core adhesion, facing thickness and profile, and the way the panel is supported all affect its performance.

Use the panel’s load tables and design calculations to establish the permissible span. The compressive grade of the EPS cannot supply this information. Wall and roof panels may differ in edge profiles, joints and permitted loads. Check the intended use before substituting one for the other, even at the same core thickness. For equipment attached to a thin facing, verify the load path and individual fastener capacity as well as the overall panel loading.

Lambda is the thermal conductivity of a material. For a homogeneous layer, thickness divided by conductivity gives its thermal resistance. For a panel, the facings and joints also form part of the product. Use the thermal transmittance stated for the actual panel variant and joint configuration.

Column junctions, flashings, fasteners and joint airtightness also affect heat loss. Two envelopes with similar performance in the uninterrupted panel area can lose different amounts of heat at their junctions. When comparing a panel with EPS-insulated masonry, compare the complete constructions, including these details.

An EPS board may have a declared reaction-to-fire class of E. This does not specify the fire resistance of a wall or roof. A sandwich panel is assessed as a product or within a defined assembly. The result depends on the joints, supports, installation direction and conditions in the classification documents.

A favourable classification for a complete wall cannot establish that the unfaced EPS board is non-combustible. Reaction to fire and fire resistance describe different aspects of performance. State the requirement for the finished element in the order and verify that the offered panel and installation fall within the classification’s scope.

Depending on the application, insulation boards are bonded, mechanically fixed or held in place by overlying layers. A sandwich panel relies on its specified joints, supports and fasteners. Cutting a facing or introducing a large service opening can change the structural behaviour of the whole panel and requires assessment.

Filling an exposed core with a piece of EPS and covering it with sheet metal may leave a damaged panel inadequately repaired. The repair must restore weather sealing, attachment and the required panel performance. Adding insulation to an existing envelope also requires a connection detail. Extra layers add load and can alter moisture conditions and fire behaviour.

An EPS quotation should identify the board, thickness, conductivity and declared properties for the application. A panel quotation also needs facing specifications, joint geometry, load tables and installation instructions. Core density cannot replace these documents. Confirm whether the quoted price includes the complete envelope element.

EPS board manufacturers include Termo Organika, swisspor, Arsanit and Paneltech. Start with the function of the proposed wall or roof. A separate EPS board may suit a built-up roof, while a sandwich panel provides a different way of forming the envelope. Compare materials once the construction method is defined.