There are many factors that go into determining the breathability of a shoe. The most breathable shoes come from brands that specialize in athletic footwear. This is because they are designed to be lightweight and allow for maximum airflow. Some brands, like Nike, have even gone so far as to produce shoes with holes in them to increase airflow.
There are also other factors that contribute to a shoe’s breathability rating such as seams and stitching which can disrupt airflow or create pressure points on the feet, reducing their ability to breathe.
Some materials like leather or suede do not allow air to flow