... no power roof fan/Roof fan/ventilating device (1) produce air convection heat radiator side by side. (2) reduce indoor ... by side.(2) reduce indoor temperature, increase indoor air fresh.(3) to reduce air conditioning load, increase the cooling effect.(4) moisture, ... cost of stents, save electricity, decrease noise.(6) Apply to factory, warehouse, building, the villa, tiantai small yard, greenhouse, ...