When renovating a floor, the choice between PIR, EPS, XPS and a suitable mineral wool board must account for the height of the entire assembly. Other layers sit above the insulation, while the finished level affects doors, thresholds and adjoining rooms. Before comparing board thicknesses, establish the actual substrate level and the requirements of the proposed floor construction. A shared section drawing then shows whether an option fits and what it changes at the edges. This guide explains how to prepare measurements and discuss alternatives with the designer. It does not prescribe a universal insulation or screed thickness; it helps compare solutions selected for a particular renovation.

Different insulation materials can work together in one building element when each solves a specific problem. PIR can keep the build-up thin, mineral wool can contribute to fire protection or acoustics, and XPS suits certain applications exposed to moisture and compressive loads. The order of the layers, how they interact and the details of their installation determine whether the combination works. Adding their thermal resistances is not enough. In a roof retrofit, serviceable insulation can often stay in place while a new layer improves the whole assembly. In a floor, thermal insulation and a resilient layer for impact sound have different jobs. Combining materials is a design decision.