Natural ventilation to the house with unplugged air conditioning

When the hot season comes, many families are trying to close the doors and windows all day, relying on the cold air to cool down. As a result, while a large amount of power resources are being consumed, indoor air pollution is also increased, resulting in discomfort of the family members. If you can use natural ventilation, you can get healthy and energy-saving! In fact, even in ordinary houses, simple natural ventilation can be carried out. If you are preparing to renovate your home, you may wish to ask the interior designer for the appropriate requirements.

Natural ventilation refers to the process of providing or extracting air from indoor spaces in a natural way. The so-called "natural method" is to provide ventilation and space cooling by using a difference in air pressure between the building and the external environment without using a fan or other mechanical device in providing or pumping away air.

The benefits of natural ventilation

In the case of the general environmental impact of the use of general energy, the use of natural ventilation is absolutely beneficial. Natural ventilation not only provides ventilation (outdoor air), but also does not require the assistance of fans or other mechanical devices to ensure the health of the residents, provide a comfortable environment for the residents and cool the indoor environment.

After careful design, natural ventilation can reduce construction and operating costs and reduce the energy consumption of air conditioners and fans. In addition, since there is no mechanical device such as a fan in the room, the noise in the room can be reduced.

Types of natural ventilation and their design considerations

Basically, natural ventilation that can be applied to buildings can be divided into two types: wind driven ventilation and hot pressing ventilation. Both types of natural ventilation are caused by naturally occurring air pressure differences. However, wind-driven ventilation uses the difference in air pressure caused by natural wind, while hot-pressure ventilation uses the pressure generated by the rising buoyancy caused by the difference in temperature and humidity. Therefore, we need to adopt different architectural designs to maximize the effectiveness of these two natural ventilation methods.

Wind driven ventilation

When natural winds blow through a building, the wind creates a direct positive pressure on the windward wall of the building, and the airflow around the building creates a negative pressure as it leaves the leeward wall of the building. Known as the "sucking effect." If there are any openings in the windward or leeward walls of the building, fresh air enters the openings in the windward walls and then flows out of the openings in the leeward walls, balancing the pressure on the windward and leeward walls.

The shape of the building is very important for the use of airflow from the wind as a ventilation for the building. The shape of the building can create wind pressure that effectively drives airflow through the open portion of the building. Of course, there are many other considerations for the ventilation design of a building. In the design guidelines for many building codes, the following recommendations are usually made:

• The orientation and location of the building (when the ventilation capacity needs to be adjusted to the maximum, a windy location should be chosen for the building, and when designing the building's seating orientation, the windward wall should be designed to be perpendicular to Local wind direction in summer);
• The shape and size of the building (buildings that use natural ventilation should not be designed too deep, otherwise it is difficult to transport fresh air to every part of the building);
• Type and use of windows;
• The type, shape and size of the opening;
• Construction methods and details;
• External element
• Coordinate with urban planning considerations.

Heat pressure ventilation

Natural ventilation generated by rising buoyancy can be caused by temperature differences (such ventilation is also known as hot-pressure ventilation) or due to humidity differences (this type of ventilation is also called cooling tower) . A prerequisite for the occurrence of hot pressing ventilation is the temperature difference. When the less dense warm air in the building (usually emitted by the households and the electrical equipment they use) rises, the lower temperature fresh air enters the interior of the building from the lower opening. This process can be seen in the illustration below.

Thermal pressure ventilation design considerations:

• The air inlet that allows airflow to enter should be placed in the low position of the room. The air outlet should be placed on the other side of the room facing the air inlet and at a high level.
• The vertical distance between the air inlet and the air outlet should make full use of the principle of hot pressing.
• Use skylights or roof vents.
• When the hot-pressure ventilation technology is incorporated into the architectural design, the positive pressure of the sealed fire escape ladder cannot be affected.

The hot pressing ventilation method does not depend on the wind. Even in the windless summer, the naturally occurring hot pressing action produces a relatively stable air flow. In addition, since the hot pressing does not depend on the wind pressure and the wind direction, it is also possible to have greater autonomy in the arrangement of the air inlet.

Natural ventilation design strategy

In the design of natural ventilation, the design concept of the two ventilation modes of wind drive and hot pressing mentioned above should be fully utilized. It can be widely used in the design of the whole building; in small apartment houses, it is also possible to choose the appropriate method and flexibly transform it. In general, the areas to consider in the design include:

• Increase air circulation by reducing air input from the outside (such as plant or site obstructions) or internal obstructions (such as furniture and internal partitioning);
• The air inlet and outlet of the room should be placed in the opposite pressure zone of the room. This includes openings in the windward and leeward walls or openings in the windward walls and roof;
• All rooms should have an intake and outlet, and at least one of the openings is fitted with an adjustable window to control the airflow;
• Air inlets that provide air should be placed in the low position of the room. The air outlet should be placed on the other side of the room facing the air intake and at a high level.
• When designing the longer side of the building and the majority of the opening orientation, the windward wall of the building should be perpendicular to the local summer wind direction;
• Use skylights or roof venting windows. They discharge rising warm air and allow heat to be discharged outside the building, allowing the room to reach a comfortable temperature at night. At the same time, they can also be used as a good outlet for wind driven ventilation;
• At least three meters of vertical space from floor to ceiling;
• The window area should not be too large, and it should be protected by shading devices or plant cultivation outside the building;
• The design should use high heat capacity and exposed ceilings for night cooling;
• Use a light colored building façade to reduce the heat absorption of the walls due to exposure to sunlight;
• Use trees/shrubs to provide shade and evaporative cooling, and use turf and other floor coverings to keep the ground cool;
• Use ponds and fountains to enhance the effect of evaporative cooling, and the water body should be placed in the upwind, so that the temperature of the wind blowing into the building is lower;
• The amount of heat generated indoors should be kept at a low level.

The many considerations mentioned above can be divided into two categories: one is to increase air flow, and the other is to reduce heat gain, thereby using natural ventilation to reduce the temperature inside the building. Mechanical cooling and ventilation systems are used to assist the natural ventilation system if necessary. Of course, natural ventilation also needs to be combined with other various green building design methods to achieve the best overall results.

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