To provide a method for promoting heat release from the surface of a waterproof layer by utilizing mechanically generated air circulation to reduce heat generation in exposed water-insulating waterproofing.

An air suction cylinder (4) and a mechanical air exhaust cylinder (5) to be always operated are installed passing through a waterproof layer (1) and an insulating layer (3). With the power of the mechanical air exhaust cylinder (5), air sucked from the air suction cylinder (4) is moved in the insulating layer (3) and exhausted from the mechanical air exhaust cylinder (5). When the air is moved in the insulating layer (3), the air absorbs heat from the reverse face of the waterproof layer (1) and always releases the heat to the outside. Thereby, the heat release from the waterproof layer (1) is promoted to reduce heat generation.