The renovation project is a house near Deshengmen in Beijing. The biggest "feature" of this house is that it is a semi-basement. The house has a total of 65 square meters and has 2 bedrooms, and the apartment is permeable from north to south as a whole, but due to the special topography of the whole unit building, the owner's house has become a semi-basement, and the south side of the room is a normal first floor house, which can be lighted normally, while the north side of the room is half below the ground, so only two very small high windows are used for daylighting, which makes the indoor light dim and humid.We set the renovation goal of this renovation as a livable home with four rooms and three halls, solve the three major problems of ventilation, lighting and humidity at one time, and create a multi-functional space to meet the needs of a family of five people to study, work and play Multiple living conditions.The first thing to be solved is the physical problem of the house-daylighting. The area of the window outside the south master bedroom is expanded to increase the lighting surface, and the previous balcony space is also been used. Since the owner ’s house is located on the first floor and there is a small yard on the south side, we have also organized this yard so that the owner can enjoy the view of the yard from the inside, and also provide an activity space for the elderly and children. The windows on the north side of the house have also been expanded within a reasonable range. The daylighting surfaces of the outside windows are all increased.If you want to accommodate a family of five in a space of 65 square meters, if you want to achieve four rooms and three living rooms, if you only consider the plane layout, it is difficult to achieve. After all, a skillful wife cannot make meals without rice, there is no area, and there is no place to put the function. So we introduced the " Folding space ", so that the function of the space can be changed, so as to increase the utilization rate of the space, but also create more space experience.