I have an old house and had to rerun the dryer vent line from the first floor through the basement and then to the outside of the house. I basically replaced everything the previous owner did with few exceptions. I used the 4" semi rigid aluminum vent hose and replaced the external vent hood. The old installation did not have cutouts in the floor joists for the vent line due to the presence of water, gas and electric lines in the path. What can I use as a hanger to help support the 4 inch line as an alternative to cutting the joists?
You can use metal pipe hanging tape to hold it up. It comes in a roll and has several holes in it which you would use to attach it to your framing with nails or screws. Simply cut it to length with a pair of aviation snips, and nail or screw it up.
Once thing you want to be careful of is not to put it on too tight and crush the vent line.