When clothes start taking two cycles to dry, most people assume the dryer is getting old.

But sometimes the dryer is working perfectly — and the real problem is hidden somewhere else.

I’m up on the roof during an inspection when I come across the dryer vent. From a few feet away, it looks pretty normal, but when I get closer I can see that the underside of the vent cap is packed with lint.

Not just a little dusty or dirty. There’s enough lint built up that there’s barely any room left for the dryer to push air out of the house.

That’s what makes this one easy to miss. If the vent was on the side of the house, you might notice the buildup while cutting the grass or walking around the yard. But this one is on the roof, and most people are never going to climb up there to check it. And most people shouldn’t. Climbing on a roof can be dangerous and not for eveeryone.

Inside the house, the dryer can still run, heat up and sound completely normal. Meanwhile, every load is trying to push hot, damp air through an opening that’s becoming more and more restricted.

Eventually, the clue may show up somewhere completely different: the clothes start taking longer to dry. One cycle becomes two, the dryer may feel hotter than usual, and the natural assumption is that the appliance is getting old or starting to fail.

But in a case like this, I’d be looking at the vent first.

The dryer may be working just fine. It just can’t get rid of the air it needs to.

A dryer doesn’t just heat your clothes.

It also has to move the warm, moisture-filled air out of the dryer, through the duct and outside the house.

When lint builds up inside the vent, the exterior hood becomes plugged, the duct gets crushed or something else blocks the airflow, that moisture can’t escape efficiently.

The result can be:

Most dryer manufacturers specifically lists longer drying times as one of the most common signs of restricted dryer venting.

There’s also a safety reason to pay attention.

The U.S. Fire Administration says failure to clean was the leading factor contributing to ignition in 31% of reported home clothes-dryer fires from 2018–2020.

If your dryer seems to be taking longer than it used to, don’t immediately assume you need a new appliance.

Start with the simple stuff.

Run the dryer and go outside to the exhaust vent.

You should be able to tell that air is moving through the vent and that the exterior flap is opening freely.

Look for:

If you can see significant lint buildup like the vent in the photo, there may be more lint inside the duct that you can’t see.

That’s when the entire vent run should be checked and cleaned rather than simply pulling the visible lint off the outside.

It’s generally recommended to clean your dryer vent ductwork every year, while manufacturers also recommend periodic inspection and cleaning based on the installation and dryer performance.

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Want to learn more about TOPIC?

🐰 People — A Literal “Dust Bunny” in the Dryer Vent
A homeowner discovered an actual rabbit trapped in a damaged dryer vent hose. Probably not the kind of lint problem anyone expects to find.
See the “dust bunny” story

🏠 Dryer Vent Cleaner — What Happens When the Vent Is on the Roof
This one hits especially close to this week’s inspection. It shows how roof dryer vents can become heavily packed with lint, why they’re so easy to overlook, and some examples of roof caps that weren’t even designed for dryer exhaust.
See what plugged roof vents look like

😬 Dryer Vent Cleaner — The Dryer Was Replaced… But That Wasn’t the Problem
One of the more surprising things about restricted venting is how easily it can be mistaken for a failing appliance. This page includes examples of homeowners dealing with slow drying and other problems before discovering the vent itself was the culprit.
See the warning signs homeowners miss

They had already lived in the house for a year.

The heating bill had tipped them off that something major had been missed when the home was built.

Then I opened the attic hatch.

What I found up there was hard to believe. 🏠🔎