The short piece of duct between the back of your dryer and the wall is called the transition duct. It is the part most likely to be crushed, kinked or made of the wrong material, and it is one of the most common lines in a home inspection report.
The four types you will find behind a dryer
| Type | What it looks like | Our advice |
|---|---|---|
| White vinyl or plastic | White, flexible, ribbed | Replace it. It can melt and burn, and many codes and dryer manuals do not allow it. |
| Foil (thin, accordion style) | Silver, very flexible, crushes easily | Replace it. It sags, crushes behind the dryer and the deep ribs hold lint. |
| Semi-rigid aluminum | Silver, holds its shape when bent | A good choice for the transition from dryer to wall. |
| Rigid metal with a smooth inside | Solid pipe | The right choice for the run inside walls, floors and ceilings. |
What building codes generally say
Most New Hampshire towns build to codes based on the International Residential Code. In general terms, it calls for the exhaust duct to be smooth-walled metal, usually 4 inches in diameter, for any flexible transition duct to be a type listed for dryer use and kept short, and for the vent to end outdoors with a backdraft damper and no screen. It also limits how long the duct can be, with each bend counting against that length. Check with your town's building department if you are changing the vent route, since local rules and your dryer's manual can be stricter.
Why the transition duct matters so much
Dryers get pushed back against the wall after every move, every floor cleaning and every repair. A foil duct folds flat in that space, and a flattened duct is a restriction even if the rest of the vent is clean. A semi-rigid duct keeps its shape and has shallower ribs, so less lint catches inside it.
What we do on a cleaning
We check the transition duct on every visit and show you what we find. If it is foil or vinyl, replacing it with semi-rigid aluminum is a $49 add-on, done while the dryer is already pulled out. On gas dryers we leave the dryer and the gas connection where they are; anything that requires moving the gas line is work for a licensed gas fitter.
Selling your home? See dryer vent fixes for home inspections.
Book a cleaning
Standard vent $149, about an hour, before-and-after airflow readings. Based in Portsmouth.
Book a cleaningOr call or text 603-660-9800