Why does wrapping a house with plastic sheeting, typically Tyvek, reduce advective heat loss?

Tyvek reduces heat loss in the winter and reduces cool air loss in the summer because it seals the exterior of the house from the wind blowing thru all the fine cracks that you could never seal.





http://www2.dupont.com/Tyvek_Weatherizat鈥?/a>Why does wrapping a house with plastic sheeting, typically Tyvek, reduce advective heat loss?
Tyvek is over rated and over priced. You can accomplish the same thing with 15# felt and button caps.