I wonder if you could help me out with this one. I have been advised that flexible plastic vent ducting is not allowed from bathroom vents. It could allow a fire to escape into the attic. Please see the attached photos.
In this case, metal ducting was used almost to the wall, but metalized flex duct, the slinky kind, was used between the solid ductwork and the wall, as well as from the fan unit to the solid duct work. In addition they used aluminum tape to seal all the joints in the solid ducting, but used “Duct Tape” to finish the connections.
What say you?