To enhance noise insulation effect and, at the same time to perform thermal insulation and prevention of dew condensation by forming hollow bodies near existing wall surfaces such as ceiling surface, floor surface, wall surface or the like of a building independently from these.

With respect to an existing wall surface 1 of a building, an upper rail 8, a lower rail 9 and supporting fittings are fixed at a position 5 to 300 mm away from the wall surface 1, an outer-side surface member 3 and an inner-side surface member 6 are adhered to the outer side and the inner side of the supporting fittings respectively thereby forming a hollow body 4. A hollow body 7 is formed by the same procedure. In this way, a hollow body 5 is formed by the inner-side surface member 6 of the hollow body 4 and the outer-side surface member 10 of the hollow body 7, and a hollow body with a triple construction is formed at the wall surface 1. In the same manner, hollow bodies 35, 36, 37 of a triple construction can be obtained at the ceiling surface 23. A hollow body 45 is formed at the floor surface 24. Any of these hollow bodies exist separately and independently from existing wall surfaces or the like through the spaces 2, 40 and 46, the influence of wall surface or the like as a propagation substance of a sound source can be eliminated and, at the same time, a high insulation effect can be obtained and formation of dew condensation can be suppressed.