The fixings for a photovoltaic array must suit the specific roof and the loads it will carry. Metal tile roofing, trapezoidal sheets and sandwich panels each require different details. Trace the load path from the modules to the building structure. Watertightness and protection of the coating matter just as much as load capacity. You cannot choose a suitable mounting kit by looking at the covering alone. Identify the roof type, condition, thickness, support spacing and substrate. Include structural drawings and details of past alterations. On older roofs, also check the existing fixings and look for corrosion. Room for modules does not necessarily mean the roof has spare load capacity.

The designations EI and REI describe how a wall or roof performs when exposed to fire. Each letter identifies a function and the number gives a period under specified test and classification conditions. With sandwich panels, the installation arrangement is part of that assessment. Read these details together to judge whether the assembly meets the design requirements. R describes its ability to carry load during fire exposure. E stands for integrity, its ability to limit the passage of flames and hot gases to the other side. I stands for insulation, which limits the temperature rise on the unexposed face. An assembly must meet each criterion required for its intended role.

Fire safety depends on choosing a panel with documented performance and installing it in the assembly covered by that documentation. The core designation and steel facings tell only part of the story. Panel joints, supports, fixings and service penetrations all play a part. Mineral wool panels are often chosen for walls with demanding fire requirements. Check the documents for the specific application in each case. The designer establishes the requirements for the building and its individual elements. An exterior cladding wall serves a different purpose from a wall separating fire compartments. The building’s function, structure and use determine the performance needed. The appropriate panel classification can therefore differ between halls and warehouses.

A building envelope must limit heat loss and meet the building’s safety requirements. When choosing sandwich panels, consider those two tasks together. PIR provides good thermal insulation with a relatively thin core. Mineral wool may be preferable where fire performance is a priority. Check the properties of the particular panel, the joint detail and the intended use. A heated warehouse, a cold store and a hall without continuous heating have different needs. The internal temperature and humidity, the materials stored and the requirements for the wall or roof all matter, as do wind loads and exposure to the elements. Without this information it is difficult to judge which panel suits the building.

Sandwich panels can form the walls and roof of a home, but the panels alone do not make a complete building system. A home also needs a supporting structure, carefully designed connections, building services and suitable finishes. Prefabricated panels can enclose the frame quickly. The final cost and the comfort of the occupants, however, depend on the whole building. When comparing promises of faster construction, check exactly which stages they cover. A sandwich panel has two facings bonded to an insulating core. Steel facings with a PIR or mineral wool core are common. Wall and roof panels span between supports and carry specified loads. They do not replace the house frame, foundations or all of its bracing.