For the ground floor of a building, thick concrete slabs are typically used. These are either supported on foundations or laid directly on the subsoil. Insulation can go above or below the slab, but you must consider how the building’s occupants will use the heating. If the building is to be in continuous use, install insulation under the concrete slab in order to utilise the thermal mass of the slab as a cover over the insulation.
In ground floors, moisture moves in two, opposite directions. Diffusion moves moisture downwards from the warm room space towards the colder soil. Capillary moisture movement lifts the moisture up from the ground towards the living spaces regardless of the temperature difference. Insulation must allow the diffusive moisture to move downwards and prevent the capillary moisture from moving upwards by creating a capillary break. In addition, the insulation under the floor slab also has to carry two loads: the casting load and the continuous loads from use. All of these requirements place special demands on under-slab insulation.
To meet the challenge of concrete slabs on the ground, use the classic PAROC stone wool solution. Porous stone wool allows casted concrete to dry about 30 % quicker than with other insulation material. And as the stone wool is a non-capillary material, there is no risk for moisture absorption.