Question about ducting kitchen through roof

rutledj

I'm installing a duct for my kitchen microwave that will go straight out the wall then up through the garage attic.

2 questions:

1. Does this duct work need to be insulated going through the garage or garage attic?

2. What is the proper fitting to use (or method) to secure the duct? Is there a special fitting for going through the roof that acts as a support? My roof vent just has a large hole in the bottom for the duct to come into. It is larger than my 6" round duct (I guess it is a universal fit).

thanks,
rut