Generally, the house is ventilated by damp, but there is one situation that must not be ventilated. In Guangdong, especially when you return to the south in spring-that is, after a few days of cold weather when the north wind blows, the south wind suddenly blows wet and warms up, or it is rainy and rainy, it is best not to open doors and windows, because the temperature of indoor ground walls and some furniture will decrease when the weather is cold. If the weather gets warmer, open the doors and windows for ventilation, and the warm and humid air outside will enter the harmful room and contact with the low temperature. Therefore, at this time, only when the outdoor temperature is low in the morning, you can properly open the doors and windows for ventilation. At the rest of the time, you can't open the doors and windows or open the exhaust fan, because at this time, the dry air in the room will be pumped away, and the humid air will flow into the cracks in the doors and windows, making the room humid.
If it is already wet, you can close the doors and windows and mop the floor with a dry floor, and it will get better in about half a day. It is better to dehumidify with a dehumidifier, but you should also close the doors and windows. It is also possible to dehumidify with an air conditioner, but you should also close the doors and windows.
If it is low temperature and humid, ventilation should be given priority to, or heating can be turned on to drive away the humidity.
There are also residents on the first floor. If the ground is wet, we should consider the problem of underground moisture regain. If so, we can only resurface the ground, do a good job of moisture-proof and waterproof about one and a half meters underground and under the wall, and then lay floor tiles and oil walls.