The heat loss caused by cold air invasion is that the cold air inside the building is invaded by the open outer door under the action of wind pressure and hot pressure in winter, and this part of cold air will be heated by the indoor temperature. The heat consumed by this part of heating process is called the heat loss caused by invasion.The cold air invaded when opening the outer door can be multiplied by the basic heat consumption of the outer door by the corresponding additional rate found in the Practical Heating and air conditioning Design Manual