When should you choose a 150 mm or 200 mm mineral wool wall panel?

Write down the objective before comparing prices. This helps avoid paying for extra thickness that serves no foreseeable use. If a change in building use is planned, compare the present and future operating scenarios. A possible need for heating may justify a different panel, provided it is an explicit design assumption.

One mineral wool wall panel range has a stated Uc of 0.27 W/(m²·K) at 150 mm and 0.20 W/(m²·K) at 200 mm. The extra 50 mm reduces heat transfer through that particular panel. The percentage reduction in the energy bill for the whole building will depend on its other heat losses too.

For 250 m² of wall and a temperature difference of 20 K, the difference in heat loss at that moment is 350 W, calculated as 0.07 × 250 × 20. The annual effect depends on the weather, heating schedule and other heat losses. Doors and ventilation can account for a substantial share.

For the same range with two 0.5 mm facings, the respective weights are about 23.1 and 28.1 kg/m². The additional 5 kg/m² adds 1,250 kg across a 250 m² façade. The designer must account for this weight alongside the other loads and establish how it will be transferred to the frame.

The length and width of each panel also matter. When replacing a wall in an operating building, check access for lifting equipment and room to manoeuvre. Tell the installation team about the heavier configuration before delivery so the lifting and support arrangements can be checked.

A thicker replacement wall can bring the inner face closer to control cabinets, pipes or door tracks. Measure the space to open covers and remove components for servicing as well as the gap at rest. If equipment needs moving, include that work in the comparison. A few centimetres barely show on a plan of the whole building but can prevent access to a cabinet beside the wall. Resolve such clashes before ordering panels.

A thicker panel may form part of assemblies with different fire resistance ratings. To establish the rating, check panel type, vertical or horizontal installation, span, fixings and direction of fire exposure. Thickness alone does not establish a class.

Where the design specifies an EI class, select a complete wall assembly with the appropriate junctions, openings and supports. A thicker panel alone cannot guarantee compliance. The reaction-to-fire class A2-s1,d0 describes a different property and is assessed separately from EI fire resistance.

Changing thickness affects flashing depths and fastener lengths. On a refurbishment it may mean moving components around a door, adapting sills or redesigning the junction with an existing plinth. Price this work together with the panels to see the full cost difference.

For a new building it is easier to set out windows, doors and framing before panel manufacture. Check junctions from inside as well. An extra 50 mm can matter in a narrow passage, beside racking or where services run along the wall.

For long heating periods, compare the full cost of each option against the building’s energy balance. If the building is heated only occasionally, other improvements may have more impact. Check airtightness, door controls and ventilation, since losses there can limit the benefit of extra insulation.

Keep the figures for both options and the assumptions behind the decision. They make it easier to reassess the choice if energy prices or building use change. A 150 mm or 200 mm panel is a good choice when its thickness meets an identified need. Thickness on its own is an unreliable measure of quality.