what insulation does everyone use ???

[cromag]

blue can foam or fiberglass to fill a gap between a window and the jamb?

[Window4U (IL)]

Red can (Hilti) is easier to use, less messy and does a better job. Fiberglass is an inferior method around windows.

[Delaware Mike]

low-expansion foam from either Dow, OSI, or Hilti. Under the sill 100% of the time. On some installs I'll use a combination of spray foam, fiberglass and Lamatek either foam. Since Lamatek is only about 25 minutes from me, I have had them make me rolls of all different thickness and width. Sometimes on a really tight window install or if the opening is really racked, the Lamatek foam insulates where I can't get a good bead of spay foam around the window.