The drainage system design of aluminum curtain walls requires a multi-layered barrier combining "blocking" and "drainage," integrating the principles of pressure equalization, gravity guidance, and material sealing technology to systematically solve the problem of rainwater infiltration. Its core logic lies in eliminating the three conditions for rainwater infiltration—pores, water accumulation, and pressure difference. Simultaneously, through rational drainage path planning, small amounts of rainwater entering the curtain wall system are quickly discharged, preventing stagnation and leakage.
Pressure equalization chamber design is a key technology to prevent leakage caused by pressure differences. Aluminum curtain wall profiles often incorporate pressure equalization chambers, which are balanced with the outdoor air pressure through special pressure inlet holes. For example, when rainwater comes into contact with the curtain wall, the pressure inside the pressure equalization chamber is the same as the outside, preventing rainwater from being drawn into the interior due to pressure difference; and areas not in contact with rainwater, even if a pressure difference exists, avoid leakage due to the lack of a water source. This design is particularly typical in unitized curtain walls, where a double pressure equalization structure of the front and rear chambers forms a continuous waterproof barrier. Even if a small amount of rainwater enters the front chamber, it will be discharged through the gap in the next panel due to gravity, preventing infiltration into the interior.
Gravity-guided drainage path planning ensures rapid rainwater discharge. Aluminum curtain wall drainage systems typically rely on gravity, guiding rainwater to the outside through a reasonable slope and channel design. For example, the inner flanges of the curtain wall beam profiles are raised to prevent water from overflowing from the channels; simultaneously, small drainage holes are created on the profiles to collect and directly discharge infiltrated rainwater. For vertically installed curtain walls, vertical drainage channels can be installed in the keel system, with drainage outlets at regular intervals; for horizontally installed curtain walls (such as canopies), drainage gaps must be left between panels, and the edges sealed with sealant, while drainage channels are installed to direct rainwater to the outside of the building.
The selection of sealing materials and construction techniques directly affect the waterproofing effect. The joints, operable windows, and junctions with other structures of the aluminum curtain wall are critical areas for waterproofing. High-quality silicone sealant and weather-resistant adhesive must be used, ensuring that the sealant width and depth meet standards (e.g., 10-15 mm wide, 5-8 mm deep). The substrate must be thoroughly cleaned before application to prevent oil stains and dust from affecting adhesion. For example, the sealing strips for operable windows should be made of elastic, weather-resistant materials, and a double-seal design should be used to reduce rainwater backflow caused by wind pressure differences. Furthermore, the processing precision of aluminum profiles must be strictly controlled to avoid excessive gaps due to excessive bending or twisting.
Combining layered drainage with a "blocking and draining" system improves system reliability. In complex curtain wall systems, such as unitized curtain walls, a "cross-joint" sealing design is often used: sealant is applied at the connection between the water channels of two unit panels, and a waterproof rubber sheet is added to the front cavity to form a front seal; double-layered elastic sponge is used at the junction of the aluminum alloy water channel and the column to seal the gaps. Simultaneously, rainwater entering the front cavity is drained to the next panel by gravity, while a small amount of rainwater in the rear cavity flows into the front cavity through a drainage chamber and is eventually discharged outdoors. This layered drainage design ensures organized rainwater flow, preventing stagnation.
Detailed treatments enhance the waterproof barrier. The top, bottom, and edges of the aluminum curtain wall require special treatment. For example, an aluminum capping plate is installed at the top, and sealant or gaskets are applied to the longitudinal joints to prevent rainwater infiltration; drainage channels or collection troughs are installed at the bottom to direct rainwater to the drain pipes; and water-resistant plates are installed on the sloping sections to reduce water flow velocity and prevent water accumulation. Furthermore, waterproof membranes are used at the connection between the curtain wall and the main structure.
