First off let’s get something straight. Many builders will defend their practices claiming they are perfectly acceptable. But by law depending on where you live this is not generally not considered a legal install.
Code states that the dryer exhaust must vent outside and installing the vent near an attic vent does not meet code requirements. Using a proper exhaust vent and everything is fine but venting into the attic itself is unacceptable and yet it occurs far too often.
The way a clothes dryer exhaust is installed can cause serious dryer vent installation in your home. Mildew can grow and cause illness in just a short period of time. In fact the moist humid atmosphere is perfect for mildew conditions. But worse yet is the fire hazard. The lint is highly combustible and any heat source could be enough to start a fire.
Dryer venting isn’t quite as simple as many think it is. So let’s unravel the mystery. As the dryer runs the blower motor pushes the moist air out but the problem is it can only push the air a limited distance.
If the run is too long the vent pipe itself will become clogged with lint and pose a fire hazard. The type of exhaust hood, the type of pipe, and even the number of bends affect how long the run can be.