Intermediate floor insulation has become more common with underfloor heating. To ensure that the heat is directed towards the floor and not the downstairs ceiling, thermal insulation must be installed in between. Insulation of the intermediate floor is also necessary when there is a cold room in the basement, for example.
The thermal insulation capacity of Finnfoam is approximately five times that of wood. If the floor is covered with approximately 10 mm of wood, and 90% of the heat should be directed toward the floor, you need approximately 20 mm of Finnfoam under the underfloor heating (hydronic or electric).
For underfloor heating at sites where both sides of the intermediate floor are surrounded by a heated space, the recommended thickness of Finnfoam is 30 mm. In between heated and cold spaces (such as a potato cellar at +5° C), the recommended thickness is 100 mm.
Even at such low thicknesses, the sturdy Finnfoam can easily withstand loads during construction. The impermeability of Finnfoam will come in handy in case of water damage. The Finnfoam thermal insulation will remain dry, and thus the structures will be easier to dry out. Even small leaks can be detected early, as water cannot collect inside the Finnfoam insulation and gutters down to an area where it is visible. The Finnfoam thermal insulation products also absorb impact sounds, even though Finnfoam is not an actual sound proofing product for floors.