The minimum water tightness index of aluminum alloy doors and windows can be determined by the following formula, and it shall not be less than 250Pa (i.e. the water tightness index of aluminum alloy doors and windows shall not be lower than Grade 3):

P=k×μz×μs×W0

Where p: water tightness design value (PA);

W0: basic wind pressure (n/㎡);

μz: coefficient of variation of wind pressure height;

μs: shape coefficient, which can be 1. 2;

K: coefficient, the value of K in coastal tropical storm and typhoon area is 0. 3, take 0 elsewhere. 25。

2. Waterproof design of doors and windows (1) The most effective way to improve the waterproof and sealing performance of doors and windows is to actively adopt the principle of equal pressure in the structural design of aluminum alloy doors and windows.

(2) The overlapping part between movable fan and window frame should not be too small. The lap joint between the casement sash and the window frame should not be less than 7 mm

(3) Try to use plane door and window structure, and use little or no push-pull door and window structure. Because there is a big gap between the movable sash and the upper and lower sliding rails of sliding doors and windows, and the two adjacent sashes are not on the same plane, there is no sealing pressure between the two sashes, but there is a gap between the tops, so the sealing effect is very weak, so the waterproof sealing performance of sliding doors and windows is very poor. There are 2 ~ 3 sealing strips between the sash and the window frame of flat doors and windows. After the sash is closed and locked, the sealing strip is pressed tightly, and the middle cavity is easy to form an isobaric cavity, so doors and windows with excellent sealing performance can be designed.

(4) The aluminum alloy glass pressing line for installing glass for doors and windows should be designed in the indoor direction to avoid water seepage from the tiny gap between the glass pressing line and the window frame.

(5) For sliding doors and windows, a high enough water baffle should be designed on the indoor side, otherwise when the outdoor rainwater has a certain pressure, it will cross the water baffle and flow into the room.

(6) The upper part of the movable door sash should be provided with a flashing plate, and the lower part should be provided with a drainage hole.

(7) The exposed flat-fell seam of combined doors and windows should be reduced as much as possible, because tiny gaps cannot be sealed with sealant, resulting in leakage. When the exposed flat-fell seam cannot be avoided due to structural reasons, the two contact surfaces of the profile at the flat-fell seam form 90 degrees, which is convenient for sealing with sealant.