Re: Installing Range Vent and Bathroom Vents
Don't use flex for range vents; all of those ridges catch grease = fire hazard.
Use the recommended size ducting in galvanized. If you live in a cold clime, a thermal break at the outside wall is a good idea, it prevents the cold from conducting through the duct and minimizes a cold-plunge convection current. That's when a cold draft is emitted from your vent hood even though the outside damper appears closed.
Bath vent ducts can also benefit from a thermal break, or insulation. A hint if you don't have either- start the fan before the shower is running, so drier room air warms the metal, preventing most condensation. Having more CFM's is also helpful, as more air flow/turbulence removes some of the conditions needed for condensation.
Remove not the ancient landmark, which your fathers have set.