Using a blower door–a device that sucks the air out of your house to simulate an especially windy day–is the best way to identify where your house leaks. For many of us, a thousand little pin pricks may add up to a hole in your house the size of a window left open 24 hours a day, 365 says per year.
By using a blower door in coordination with air sealing, we can identify the biggest leaks and get them sealed. A gneral rule of thumb is 1 sq inch = 10 cfm at cfm 50.
This video from Green Building Advisor shows how it’s done.