This system is the wunda floor underfloor heating system. This is also an overlay system which is great as a retro fit system. The wunda floor panels differ to the solflex in the fact they are actually a polystyrene board covered with a Thick foil. The reason for the foil covering is to act as a spreader plate, helping to transfer the heat from the boards / pipes, to the floor covering on top. These boards are glued to the floor using a contact adhesive. Once set, it is very strong. These boards can take all floor coverings.