Re: Types of duct work
B-vent pipes are galvanized. However, chimney liners are aluminum and stainless steel. You can use aluminium in most cases for a standard efficiency non-condensing gas appliance. However, I'd still use stainless steel for durability and longevity.
FOr what it will cost you to reline the chimney, you might consider going to a condensing tankless water heater and use PVC for the vent. I have a Navien in my home and installed it for that same reason. Rather than reline the chimney, I installed a water heater I could vent with PVC.... along with other benefits like the model's built-in recirculation pump and mini storage tank. Endless hot water isn't bad either.
1925 Two-Story Stucco Beaux Arts Neoclassical