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The purpose of ventilation in naturally ventilated buildings is to provide fresh air for people to breathe or to lower the indoor temperature in summer. The development and refinement of air conditioning technology have enabled people to create a separate microclimate within a completely enclosed space, keeping the indoor temperature and humidity within relatively comfortable ranges at all times. However, air conditioning is not a panacea; the negative effects of its widespread use in modern buildings have raised concerns, prompting efforts to find solutions. Providing adequate natural ventilation in buildings is one effective way to reduce the negative impacts of relying on air conditioning. Buildings with natural ventilation can reduce air conditioning energy consumption, thereby decreasing the use of non-renewable resources needed to generate this electricity and the amount of CO2 emitted into the atmosphere ； For the human body, natural ventilation can reduce the incidence of \"air-conditioning syndrome\" and various diseases transmitted through the air. (1) Principles and modes of natural ventilation: In terms of the source of energy, natural ventilation in buildings can be divided into two modes: pure natural ventilation and mechanically assisted natural ventilation. Natural ventilation refers to the air flow between the interior and exterior of a building, which is caused by the \"pressure difference\" resulting from outdoor wind speeds, as well as the \"temperature difference\" resulting from the positions and temperatures of the openings on the building’s surface. According to thermodynamic principles, the indoor temperature in buildings increases gradually as one moves upward. This feature is the main reason why the temperature difference between the upper and lower levels increases as the building height increases; designers often take advantage of this to harness the potential for natural ventilation in buildings. Mechanically assisted natural ventilation utilizes the combination of thermal pressure caused by temperature differences and mechanical power to create air convection between the indoor and outdoor areas. Compared to complete natural ventilation, although mechanical devices used locally within the building as auxiliary means of ventilation consume some energy, reorganizing the air flow through such devices, or even \"forcing\" the air flow to change direction in certain areas, can lead to better results with natural ventilation. In both ventilation modes, the roof plays a crucial role in creating temperature differences and organizing air flow, serving an important function within the entire natural ventilation system. (II) The role of the roof in natural ventilation: When there are vertical shafts running through the entire building, the temperature difference between their upper and lower ends can be utilized to accelerate air flow and thereby promote ventilation within the building. This is essentially based on the principle of \"temperature difference – thermal pressure – ventilation\". The atrium, as a shared space in a building, can serve as this \"vertical shaft.\" Generally, it is advisable that its proportion of the total building area exceed 1/3. The roofs of such atriums generally possess two functions: 1) they allow sunlight to enter the atrium, heating the air there and creating a temperature difference between the upper and lower areas ； 2) They are fully or partially open, allowing air currents to find an exit when ventilation is needed. The HOLZ housing complex in Linz, Germany, designed by Herzog, is characterized by shared atriums with glass roofs in each building; these atriums run through five floors of the building and are slightly above the rooftops of the rooms on either side. In winter, sunlight shines in directly through the glass roof. The side windows on the roof of the atrium are closed, turning the atrium into a large \"greenhouse.\" At night, the heat stored in the atrium during the day can be radiated into the rooms on both sides ； In summer, the side windows on the atrium roof are opened, allowing the natural wind drawn in from the entrance hall to carry away heat as well, thereby cooling down the building at night. When the building volume is small and the height of the internal \"vortex\" space is not sufficient to create an effective temperature difference, it can also be designed as a vertical protrusion that extends beyond the roof. An office building in Solihull, central England, uses natural means via its roof-mounted \"solar chimneys\" to meet the lighting and ventilation needs of the office spaces. The north side of these “solar chimneys” features glass skylights, through which natural light shines into the central area of the building. Opposite the skylight is an automatically controlled movable panel; when it is opened, sunlight enters the room from the south side of the \"chimney\" to heat the air at the top. Driven by this heat pressure, air currents enter through the windows on the exterior walls, rise upward, and then exit through the \"chimney\". In addition to atriums, the building’s stairwells can also be used as \"vertical shaft\" spaces. The protruding space on the roof can be used not only as a chimney but also in the form of a wind tower or a wind cap. How to make those parts that protrude from the roof appear harmonious with it in terms of appearance, and even turn them into a highlight of the entire building’s design, is both a challenge and an opportunity for every architect. (III) The role of roofs in mechanically assisted natural ventilation: For buildings in many regions, complete natural ventilation is not suitable in every season ； Some buildings are constrained by specific conditions and do not have air flow corridors that allow air to enter at a low level and exit at a high level. At this point, natural ventilation in buildings must be assisted by mechanical devices, or there must be a rotation between complete natural ventilation and mechanical ventilation depending on different times of day and seasons. The main building of the Jubilee Campus at the University of Nottingham in the UK is equipped with two ventilation systems: when the outdoor climate is mild, air currents are guided by the recessed entrance to the atrium, enter the atrium through the louvered openings above the entrance, and then exit through the glass louvers on the roof at the other end of the atrium; this represents a fully natural ventilation mode. During hot or cold seasons, when the building’s doors and windows are closed, fresh air is drawn into the air ducts through mechanical ventilation and heat recovery systems located on the roof. From there, it enters the cavities beneath the floor slabs, and with the help of low-pressure dispersion devices installed in those floors, it makes its way inside the building ； The exhaust gas is expelled through the ventilation in the corridors and stairwells, returning eventually to the upper part of the wind tower; there it passes through heat recovery and evaporative cooling devices before being discharged through the air ducts. This is a form of natural ventilation assisted by mechanical means. Solar collectors are integrated into the heat-absorbing reinforced glass on the atrium roof, and the heat energy they absorb is used to power mechanical ventilation systems. (IV) Natural ventilation inside the roof: In addition to serving as part of the building’s overall natural ventilation system, with structures such as skylights, chimneys, and air inlets providing entrances and exits for air currents, the roof can also function as an independent ventilation system on its own. Such ventilated roofs typically have an air layer inside them; the principle of thermosonic ventilation is utilized to drive air flow within this air layer, thereby raising or lowering the temperature of the inner surface of the roof, which in turn affects the temperature of the indoor air. In Japan’s OM Sun System homes, outdoor air is drawn into the air layer at the bottom of the roof and heated by the glass collectors installed on the roof; after being heated, it rises to the highest point of the roof. Air handling units are installed at the highest point of the roof, including air valves, heat exchange coils, and a small fan. This device can deliver heated air to every corner of the building through ducts, while also removing air that does not need to be heated through exhaust vents. In a project in Munich, Germany, that involved converting a warehouse into a design studio, the thermal performance of the existing exterior envelope was not sufficient for the new purpose. Architect Herzog added an interior layer that covers the entire roof and most of the inner surfaces of the exterior walls; the air between this layer and the existing exterior cladding acts as a thermal insulation layer, providing insulation and heat buffering. Air caps that connect the air thermal insulation layer to the indoor air are installed on the roof, allowing this simple small building to choose mechanical ventilation as needed, and to regulate the indoor climate through one or more of the ventilation modes available, such as natural ventilation inside the room or ventilation within the air thermal insulation layer. Although the principle of using thermal pressure for natural ventilation is simple, the selection of specific designs or technical measures still requires consideration based on the building’s function and location ； Qualitative design alone is not sufficient; in order for ventilation to achieve a practical cooling or heating effect, it is necessary to conduct quantitative calculations of parameters such as the air flow rate at the inlet and outlet openings, the timing of opening and closing these openings, the amount of light available on the atrium roof, and the operating time of mechanical exhaust systems. At this point, methods such as wind tunnel models or computer simulation experiments are often required to obtain accurate values. The 21st century is a century for environmental protection and sustainable development. Reducing building energy consumption and achieving a dynamic balance between the artificial and natural environments within buildings represents a higher goal that should be pursued after meeting the basic functional and aesthetic requirements of such buildings. The relevant roof structures and equipment, in combination with the natural ventilation conditions created by the building’s other enclosure systems, enable the building to have greater potential in achieving the aforementioned objectives.