The advantages are large opening area, good ventilation, good sealing, sound insulation, heat preservation and good impermeability. The window cleaning is convenient with the inner opening; the open window does not occupy space when the opening is open. The disadvantage is that the window is small and the view is not open. The opening of the outer window should occupy a space outside the wall, which is easy to be damaged when the wind blows; while the inner window is to occupy part of the space inside, and it is not convenient to use the screen window. When opening the window, it is not convenient to use the screen window and curtain, such as the quality is not closed, and it may also seep through the rain.