If the insulation layer and leveling layer are not dry enough or it is difficult to dry, air holes should be reserved when paving the coil, so as to discharge the water under the coil layer. This roofing practice is called exhaust roofing. If the vent hole is not reserved, the moisture at the grass-roots level will be sealed under the waterproof layer of the coil. Once the temperature is high (especially in hot summer), the volume of water evaporation expands, and the coiled material will bulge, causing the waterproof layer of the coiled material to crack and damage, resulting in roof leakage.