Matthew Weir wrote:Thanks. There is a landfill in the area, but apparently they are against taking anything out.
Glenn Herbert wrote:If it's the right diameter it should work fine, but "silver" means galvanized, and there will be enough heat in that area to burn off the galvanizing and release toxic fumes. It is recommended to use black iron/steel in the high heat areas, and consider it a sacrificial form as much of it will burn out or corrode sooner or later (sooner in the combustion core).
Sections of round duct can be combined as needed to make the outer heat riser form to hold the insulation.