This graph shows which structural air-leaks drive up energy costs the most, allowing you to maximize efforts toward reinforcing your home's building envelope.

The graph below shows which structural air-leaks drive up energy costs the most, allowing you to maximize efforts toward reinforcing your home's building envelope. 

This image comes from http://www.builderonline.com/energy-efficientconstruction/5-penetrations-that-provide-the-most-bang-for-your-air-sealing-buck.aspx