B-vents are make to attach and adapt to a wide variety of different size chimney pipe systems. A B-vent adapter is designed to connect the primary chimney liner system to other B- vent type pipes that go to appliances. The B-vent adapt is constructed from aluminum, 3003 alloy. The sizes include three inch, four inch, five inch, five and one-half inch and six inch adapters. These adapters are ideal when you have to install components from different brand of liner systems.
What is the difference between a type B vent and a double thickness aluminum flex liner that will run the full length of an existing masonry chimney? I do not understand chimney language. Should there be insulation added between the liner and masonry chimney to insulate against heat loss from the structure being heated?
The only difference between the two is that the B-vent piping is rigid and will have a small insulating air space between the layers of material and the flex liner is two layers laid directly upon one another.
If the flex liner is run through a chimney on an outside wall, it is best to insulate it. The chimney can become very cold and will cause issues with condensation, which can lead to degradation of the flex vent.