How thick should PIR wall panels be when adding heating to an existing industrial building?

A partition between a heated workshop and an unheated store faces different conditions from an external wall. Check which requirements apply to the wall and the proposed work. For example, Annex 2 to the Polish technical conditions for buildings (2022 consolidated text, Journal of Laws, item 1225) gives a maximum corrected U-value, Uc, of 0.20 W/(m²·K) for an external wall where the design indoor temperature is at least 16 °C. Confirm the applicable provisions for the location and scope of the project.

The thermal conductivity λ describes the core material. The U-value describes heat transmission through a particular panel or wall assembly. Consult the table for wall panels with the specified core. A foil-faced PIR insulation board and a sandwich panel with two steel facings each have their own product data.

The example below covers one range of steel-faced PIR wall panels with a declared core conductivity of 0.022 W/(m·K). It shows how thickness affects the U-value within that range. Use the figures for the chosen product when specifying panels for a building.

In this range the 120 mm panel has a U-value below 0.20 W/(m²·K). Assessing the wall and the building also requires the relevant corrections and an allowance for thermal bridges. Examine the wall base, corners, loading door openings and roof junction. Heat loss at repeated junctions can reduce the benefit gained by thickening the uninterrupted wall sections.

During refurbishment, check the airtightness of the panel joints and around the perimeter of the cladding. A draught at the wall base needs attention at that junction, even if the panels elsewhere are made thicker. Check service penetrations too. Apply the same sealing detail to later openings as to equivalent openings included in the original design.

After the walls have been replaced, the old roof or a frequently opened door may account for a large share of the remaining heat loss. A heat demand calculation shows the relative contributions and helps determine the order of work. Base any estimate of savings on how the whole building will be heated and used.

A tighter envelope needs planned ventilation. Moisture from production processes, wet vehicles or washing must have a reliable route out of the building. Design the heating and ventilation alongside the panel specification, especially when converting a warehouse to a different use.

The replacement panel must suit the spacing and condition of the supports. Core thickness affects panel behaviour. Verify capacity for the design wind loads and fixing arrangement, and inspect the existing structure. Corroded supports and insufficient bearing widths need attention as part of the refurbishment.

Check fire performance, acoustic requirements and the suitability of the internal coating for the new environment. Each needs its own specification. Noisy machinery or a new production process may require an additional internal treatment. Detail it so that the building envelope stays airtight.

For each option, record the panel U-value, details at the wall base and openings, any roof replacement work and the calculated heat demand. Include removal, flashings and downtime. This shows what each panel thickness will cost as part of a complete refurbishment and how it affects projected heat use.

If work is phased, design junctions for the finished building. A temporary junction with a wall awaiting replacement must allow the next stage to go ahead. Once the work is complete, check airtightness and heating performance under operating conditions. These checks can reveal installation defects at joints that a panel datasheet cannot show.