Why do string vests keep you warm?

String vests, often made of wool or similar materials, can help keep you warm due to their ability to trap heat close to the body while allowing some breathability. The open weave design allows for airflow, which can regulate temperature by preventing overheating. Additionally, the layered effect of wearing a string vest under other clothing can provide extra insulation. However, their effectiveness largely depends on the material and the conditions in which they are worn.