Glad they were helpful. Good luck with your project.
Looks like tomorrow we're in for some Irene A** kicking. Calling for sustained winds of 55-75 MPH with gust of 105 in the afternoon. The lowest areas will definitely see flooding. Not that where we live is high, but so far it's been high enough. Lets hope our luck holds.
Don't want to be a negitive nelly but you need to insulate any duct in an attic. Especially Bathroom vents. The entire purpose of bath fans are to remove humidity out of bathrooms from showers/baths. The warm bathroom air with humidity will travel thru duct into attic, where in winter it is cold and drop it's humidity filling ducts (especially aluminum duct).
Fix is fairly easy - wrap with Foilback insulation or switch to Insulated flexible duct -which is similar duct to what u have except it is flexable plastic/wire with a layer of insulation and light plastic jacket on outside.
example here http://www.rewci.com/infldu.html
Nothing negative about your comment, it brings up a good point. I'm not sure it's code in this area to insulate vent ducts. I can't remember ever seeing it done on new construction. I've haven't seen this to be a problem in residential applications, but I have seen some condensation damage in commercial settings and I'm not sure if those ducts were insulated or not.
I appreciate your suggestion and may even get around to applying it.