PIR or mineral wool? Choosing sandwich panels for a steel building

Heated steel buildings can also be clad with mineral wool panels. The thermal calculation and the product data determine the required thickness. To estimate heating demand, include air leakage at joints and the time loading doors stand open during a shift. The core material alone tells you little about these losses.

Mineral wool is often specified where fire performance matters. Reaction to fire describes the panel’s behaviour when exposed to fire. Fire resistance is assessed for an assembly under specified conditions. Check that the classification for the proposed wall covers its orientation, fixings and span before relying on it in the design.

PIR is combustible. Check the fire classification of the complete panel and whether it is suitable for the proposed use. The steel frame needs its own fire assessment. At elevated temperatures, steel can lose load-bearing capacity even though it does not burn.

To assess noise reaching nearby buildings, trace the paths through the walls, roof, doors, air intakes and open vehicle entrances. Improving a wall panel’s sound insulation may have little effect at a neighbouring property if most sound escapes through an open loading bay.

Reverberation is a separate issue inside the building. Smooth metal facings reflect sound even when the core is mineral wool. If a workshop echoes, consider acoustic absorbers designed for the space or enclosures around noisy machines. A wall’s airborne sound insulation rating does not describe how much sound its inner surface absorbs.

Replacing a PIR panel with a mineral wool panel of similar thickness can change the permanent load on the frame. Check the actual panel weight, span, wind suction and fixing design. Also confirm how the proposed panels will be lifted into place.

On modular buildings, specifying the cladding early allows the designer to coordinate supports, openings and delivery lengths. The calculations still depend on the site. A panel suitable in a sheltered wall zone may need different fixings or closer supports at an exposed corner.

The metal facings also need a specification. In a wash-down area, check coating resistance and how joints and junctions are sealed. A dry warehouse and a humid agricultural building with a corrosive atmosphere expose the sheet to quite different conditions, even if both call for the same colour.

Identify the cleaning agents and methods in advance. Excessive jet pressure, an unsuitable chemical or a damaged coating can shorten the service life of the cladding. Specify protection for both panels and steelwork according to exposure. Keep the maintenance instructions and restrictions for the selected finish with the building records.

Mention foreseeable changes of use in the enquiry. A seasonal store might later need permanent workstations or a cold room. Sometimes reserving space for an insulated room is enough. In other cases the change calls for alterations to the envelope and services. Identifying these differences now makes a later extension easier to plan.

Price each option against the same use, temperature range and fire requirements. Include secondary steelwork, fasteners, flashings, transport and installation. A lower panel price per square metre can be offset by extra supports. An expensive core offers little value if its additional performance serves no requirement of the building.

Before placing the order, match the values in the design with the product data for the proposed thickness and facing. Record which option meets each requirement of the workshop, warehouse or agricultural building. This gives the purchaser a traceable basis for accepting a panel or assessing a later substitution.