When and how to insulate the slab?
Slab is very important for the house. It closes one storey on one side with a ceiling, and gives floor for the storey above.
Have you thought of when the slab over the last storey should be insulated, so that the cold loft is not the weakest link for the thermal insulation of the entire building? The answer is: if you attic is not used, because it is used as a storage for things you don't need. There are attics of low and rather flat roofs marked as unoccupied during the design phase.
Popular mineral wool tend to absorb moisture, so if laid on a fresh slab it will absorb water remains from the concrete slab and will as a result reduce it thermal insulation properties. An additional disadvantage of wool as well as styrofoam is that they are difficult to adjust to the shapes of the insulated surface.
The polyurethane foam is the right solution which is perfect for slab insulation. What's important: unlike wool, the foam preserves its thermal and waterproofing properties for years. Foam is applied evenly forming a uniform layer retaining heat in the building.
Slab insulation with polyurethane foam – concrete
For concrete slabs, closed-cell polyurethane foams of different densities are often used, depending on the insulation hardness requirements (i.e. mechanical resistance).
If the concrete slab is to be insulated from the top, harder foams are used. This is because they are loaded by a layer of floor concrete, building equipment and everyday use.
You can also apply foam to a concrete ceiling, e.g. in basement, and insulate the living area on the side of non-insulated rooms. In this case closed-cell foams are also used, usually of lower thickness, as ceiling insulation is not loaded.