Close, but not close enough! Bathroom vent ducting shouldn’t discharge into the attic. Instead, it needs to be routed all the way to the exterior to help prevent elevated moisture conditions in the attic area that can lead to mold growth. I also recommend insulating vent ducting in the unconditioned (unheated) attic area to help prevent condensation within the ducting itself. This was discovered at a recent home inspection in Anacortes on Fidalgo Island.
If you note that some, or any, of your black ABS vent pipes on the roof are capped, there’s a good chance that the contractor forgot to remove the caps after construction. These caps are designed to pressure test the vent and drainage system to make sure they don’t leak as a condition of the building inspection. After the test, the contractor is supposed to remove these caps but this step is sometimes missed. So, if you see caps atop your roof, take them off unless the pipe itself has been abandoned (e.g., from a remodel).
Clothes dryers evaporate the water from wet clothing by blowing hot air past them while they tumble inside a spinning drum. Heat is provided by an electrical heating element or gas burner. Some heavy garment loads can contain more than a gallon of water which, during the drying process, will become airborne water vapor and leave the dryer and home through an exhaust duct (more commonly known as a dryer vent).
(read full article on InterNACHI)