Retrofitting insulation to a steel building: what to check before buying panels

The steel structure may have been designed for a different type of covering. Load-bearing reserve should not be assumed simply because the building has stood for a long time. New panels, an additional layer or heavier equipment change the operating conditions. The foundations and the way forces are transferred from the envelope must also be assessed.

Maintaining a positive temperature in a warehouse is designed differently from workstations, and differently again from a cold store. After modernisation, a steel hall needs a defined range of temperature and humidity. The number of people, operating hours and process emissions must also be taken into account. Without this data it is difficult to select the right envelope variant.

A change of function may give rise to requirements that go beyond insulation. This applies to services, ventilation, fire protection and formalities. Steel structures are flexible in adaptation, but not every change is a minor repair. The scope of the necessary measures should be established before work begins.

Replacing the envelope allows a complete system to be selected and details to be improved. It may, however, require phased working or the temporary closure of part of the facility. Adding insulation leaves the existing layers in place but changes their thermal and moisture conditions. A steel hall requires an analysis of both routes taking into account the actual condition of the materials.

A damp or corroded envelope should not be sealed behind a new layer without removing the cause. A hidden problem will be harder to monitor. The ability to inspect the steel structure connections is also important. The modernisation detail should show where the new fixings go and how loads are transferred.

New panels will not automatically improve every point of heat loss. A steel hall may still have a leaky gate, an uninsulated floor-to-wall junction or openings left by old services. These elements should be included in the scope of work. Otherwise the improvement of the envelope will be uneven and some problems will remain unchanged.

When the wall thickness changes, the reveals, flashings and the position of equipment must be adapted. The roof requires checking of water drainage and the connections at the eaves and ridge. The steel structure should provide suitable supports for the new elements. Improvised extension of fixings on site does not replace a design.

An older building may draw significant amounts of air through leaks. New cladding can restrict this inflow. The steel hall then needs appropriate supply and extract air in line with its function. The appearance of moisture after refurbishment should not be taken as proof that airtight panels are unsuitable. The whole system must be checked.

Improving insulation can also change the heating balance. Existing equipment requires assessment and appropriate adjustment. In a production facility, heat gains from machinery and extract systems must be taken into account. Leaving the old settings unchanged may not match the new conditions, despite the improved building envelope.

In an operating facility, a plan is needed to protect goods and installations from precipitation during the works. Opening one façade bay can change conditions in a larger part of the building. It is worth agreeing the sequence of deliveries, the storage location for new panels and the route for removing old ones. Panels should not be left on the roof without checking the permissible load. The schedule should provide for stopping work in unsuitable weather. This way the pace of modernisation will not force the building to be left in a random intermediate state. Agree the works plan with each contractor.

Dismantling walls and roof requires a planned sequence. If the design accounted for the cladding acting together with the structure, removing the envelope can change its stability. In a steel hall, the need for temporary bracing must therefore be checked. Opening a large part of the wall also affects wind action during the works.

Modular steel structures make it easier to organise the stages, but each stage requires assessment. After completion, the envelope, installations and documentation of changes must be accepted. The steel hall should receive clear rules for use and inspection. The modernisation then improves working and storage conditions in a way that can be maintained later.