When should you compare 150 and 200 mm mineral wool panels?

The 200 mm option is not necessarily best. If ventilation and vehicle doors dominate heat losses, walls may account for a smaller share. On the other hand, thickening a finished envelope is difficult. Consider the building’s planned use beyond its first heating season.

In one dual-density core range, the 150 mm panel has a U-value of 0.25 W/(m²K) and the 200 mm panel 0.19 W/(m²K). With 0.5/0.5 mm facings they weigh 21.3 and 25.6 kg/m² respectively. Other ranges and geometries may give different results.

Check cover width, available lengths and fixing method. Here the difference of 4.3 kg/m² adds 1,806 kg over 420 m². Account for it in the structure and logistics as well as comparing U-values.

With identical facings the extra weight comes chiefly from the core. Compare the actual cutting schedules: a revised panel layout can change delivery weight differently from installed weight. Record two totals, one for the load on the frame and one for transport including offcuts.

Across 420 m² at a 24 K temperature difference, the instantaneous heat loss is about 2.52 kW at U = 0.25 and 1.92 kW at U = 0.19. The difference is 604.8 W for the panel field under these conditions.

This is not an annual energy saving. Annual estimates need climate data, heating hours and system efficiency, as well as the other building elements and thermal bridges. The example indicates scale but cannot establish a payback period.

The additional 50 mm changes reveals, flashing widths and the face of the wall. Check door tracks, sills and services for clashes. Decide which side will gain thickness, particularly at existing edges and insulation junctions in a refurbishment.

Size fasteners for the whole assembly, not just the thicker core. Check the plinth support too. A wide flashing is no substitute for structural bearing. A section drawing lets you price the detail before the first panel reaches site.

Greater thickness may permit a different fire-resistance class within one system. There is no universal class for all 150 or 200 mm panels. The result depends on product construction, seals, fixings, orientation and assessed spans.

Verify that openings and junctions are covered by the chosen classification. If the thinner variant already meets the requirement, extra thickness does not permit simpler detailing. Reaction to fire of the core or panel is distinct from the fire resistance of the finished wall.

Add material, flashings, fixings and any structural changes; allow for heavier transport and equipment. For a 420 m² order, an increase equivalent to PLN 1 (about €0.23) net per square metre adds €97.32 net at the unrounded rate in panels alone. Price the remaining work separately.

Choose the variant that meets the requirements and works across the enclosure. With a limited budget, compare other options too. Sealing a vehicle door or improving the plinth detail may matter as much. Let the design and calculations settle the choice.