Understanding of Unitized Curtain Wall
Unitized curtain walls can mainly be divided into "unitized curtain walls" and "semi-unitized curtain walls", also known as rigid unitized curtain walls. Semi-unitized curtain walls can further be divided into: vertical mullion sectional unitized curtain walls, window wall unitized curtain walls. The classifications of the above unitized curtain walls may vary, but their basic principles are completely consistent. They have essential differences in manufacturing, design, and construction compared to framed curtain walls.
Characteristics of Unitized Curtain Wall
Unitized curtain walls solve the problem of water leakage by adopting the "equal pressure principle". To have water leakage in curtain walls, three conditions must be met. Firstly, the presence of water, such as rain or window cleaning water. Secondly, a pathway for water movement. Thirdly, the driving force for water movement, which includes six types of forces: gravity, momentum, surface tension, capillary action, airflow, and pressure difference. Pressure difference is the main cause of most water leakage at curtain wall joints. In order for external water, whether it is rainwater or window cleaning water, to enter the interior, there must not only be openings or cracks but also the external pressure must be greater than the internal pressure. If the internal pressure is equal to or greater than the external pressure, even if there are openings or cracks, water will not enter the wall. The traditional waterproofing method is to minimize possible openings at long joints, such as using various sealants and gaskets for sealing. The new method of waterproofing into the interior is to guide rainwater into an equal pressure chamber and then drain it out of the wall.
In order to achieve equal pressure, we keep some or all of the joints open. However, the equal pressure chamber is not a ventilated space. It must be limited to a certain range of ventilation space to effectively generate equal pressure. In order to achieve complete equal pressure, the pressure in the "equal pressure chamber" must always be maintained greater than or equal to the external pressure. However, we know that the surface pressure of a building does not remain constant due to changes in wind speed. The higher and larger the building, the more pronounced the pressure difference. The positive wind pressure near the ground is smaller than the positive wind pressure higher up. The positive wind pressure in the center of the facade is larger than the positive wind pressure in the corners. The same horizontal member may experience positive pressure at one end and negative pressure at the other end, and other factors also contribute to the complexity and difficulty of designing equal pressure effects. Therefore, it required higher technological requirements for unitized curtain wall system manufacturers, and the equal pressure principle is the unique core of unitized curtain walls.
The height of the unitized components of unitized curtain walls is the same as the floor height, and the width is generally around 1.2 meters to 1.5 meters. Therefore, the transfer of forces is simple, and they can be directly hung on the pre-embedded components of the floor, making installation convenient.
The unitized components are processed and manufactured in the factory. Glass, aluminum plates, or other materials can be assembled on a unitized component in the factory, promoting the industrialization of construction.
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