I've got to clear out nests behind my shutters. First I'm going to work on depopulating them a bit with wasp trap.

They sell them inexpensively
http://www.yankeegardener.com/wasp_trap.html

Or you can make them
http://eartheasy.com/live_natwasp_control.htm

Actually, that last site gives many recs for removal of nests, but recommends using a pro if they are inside the walls like yours are. -- Good luck!