The houses in Japan have been more and more industrialized and low-priced houses are widely spreading. The improvement of the amenity of the residence has realized at the same time. In Japan, houses are designed especially to prevent the corrosion of an architectural building frame in hot and humid summer. However, there are a lot of regions in which people should provide against cold winter. Japan lies long from north to south. The present study investigates the possibility of natural ventilation in cold regions in Japan. In the houses in cold districts, in addition to energy conservation, the achievement of premeditated ventilation that improves insulation and air-tightening in the wall, the roof, and the window is indispensable. There is a lot of damage by vapor condensation and mold in the house in present Japan, and the Japanese law obligates the ventilator by the electrical energy while premeditated ventilation schemes are neglected as above mentioned. Depending on the electrical energy conceives enormous difficulties from the viewpoint of the energy maintenance and prevention of the global warming in the future. The simultaneous type ventilator that the authors are proposing requires a ventilation scheme in which the ventilation routes are based on indoor-outdoor temperature differences. If the ventilation route is shut down for some reasons, the fresh air will be coming and the exhaust air will be gone out at the same time in each room. In this report, the authors described on the basic performance of a simultaneous type ventilator, and presented some examples in which very effective ventilation results were got. Especially, the authors showed the results of the improvement of high moisture in the flower shop and the ameliorating of humidity in some apartment houses as its applications. The authors hope the present study will contribute a little to the solution of energy problems and the prevention of global warming in the future.