The concept of porch, in the past, China's house opened the door and directly saw not the living room, but a barrier called zhaobi, which is usually considered as the predecessor of the porch in modern home.
After understanding the function of the porch, you can understand that those houses need to be porch. That is to say, the entrance door of some houses is straight into the room, or the entrance door is directly opposite to the bedroom door, kitchen door and bathroom door, or there are three doors, so it is necessary to set up a porch to partition and block it, so as to resolve the adverse effects of straight entry.