Last year, I had a new roof installed and the roofer installed the stack or vent flashing. I am not sure what it's called, but it's supposed to be used for a 4" bathroom vent. Now, I am attempting to install this vent duct and noticed it looks just like the one used to cover the vent pipe. What I am wondering is there suppose to be a pipe of somesort up into the flashing to direct the air out of the bathroom and to the outside.