I just had a contractor come to install a bathroom vent fan in my attic. I told him I needed the exhaust vented to the outside of the house because I have had mold problems in the attic. I just had the attic treated for this. I was expecting him to put in a roof vent with dampers on it. However he ran the flexible duct up to the existing attic vent. He then duct taped it up against the screen on that opening. Is does not cover the entire opening, and there are no dampers. Please see photos. He said that he talked to several other people and this is the way they do it. Is this an acceptable solution? It just does not seem right to me.
That is a terrible, terrible work. Running ducts vertically requires a dryer to run longer to dry clothes, which wastes energy because it has to push warm air up. Secondly, dryer exhaust ducts should never have screens on them - they will get clogged and become a fire hazard. And while duct tape might be useful for many things, this isn't one of them! You need proper dryer exhaust duct fittings, like a louvre connection.