All cases shown above were calculated with an insulation layer of 10 cm underneath the floor slab. However, industrial buildings are often constructed without an insulation layer underneath the floor. The concrete floor is put directly on some kind of gravel to prevent the concrete from frost damage.

How much energy is lost through the floor slab of such a building depends on the physical parameters of the soil underneath. To illustrate the influence of an insulation layer underneath the floor slab and to show the influence of the soil characteristics, simulations were carried out with two extreme sets of soil parameters: very light and dry soil such as sand that doesn’t conduct the heat well and heavy wet soil such as clay that is much more dense and conducts heat well (see Table 2). As expected, the influence of the soil parameters on the heat demand of the building is much larger if there is no insulation layer underneath the building. However, the most important result is that the space heating demand is roughly doubled without an insulation layer underneath the building.