What I'm Seeing Now


The Dryer Vents Through The Roof - Is It Leaking Air Inside The Attic?

The dryer vents through the roof - is it leaking air inside the attic?

One of my pet peeves is seeing that the dryer vents through the roof.

To me common sense says it's a bad idea.

Why?  Look at the diagram to the right.  This is probably the most typical dryer vent hood that I see when it is installed on a roof.

This about why I don't like seeing this. 

1.  How do you know when the dryer vent is clogged?

YOU SEE IT.  When the vent is on the roof, how can you see it?  At this subject house, a townhouse, I could not see the rear roof from the yard.  It was three stories high.  To see the dryer vent I had to go to the end of the townhouse row behind and look at it from a distance with my 20X binoculars!  And even then I could not tell.

2.  What do you do when the dryer vent opening is clogged?

YOU CLEAN IT.  How do you do that when the vent opening is high on the roof?  Someone needs to go on to the roof!  At this house you would need a very tall ladder, or hire a company with one.  This height would require two people to manage the ladder.  Then you would have to trust that they did a good job.

3.  How often does the dryer vent need cleaning?

WHEN IT CLOGS!  How many people live in the house?  How often do you do wash?  Do you wear a lot of cotton that creates more lint?  Is the weather cold where you live (which creates more condensation at the vent opening, making it stickier)?  So the answer to #3 is - who knows!

So, from inside this attic the view you see in this photo is about the view I had when up there.

The sheathing is about 18' above the attic access opening.

I see what looks like stains on the sheathing and roof framing.

I see what looks like lint, or maybe white fungus.

I see what appears to be lint blowing in the breeze.  It's really hard to tell if it is clogged and leaking back into the attic.  So how can I find out?

To test this I turned on the dryer and waited about 10 minutes.  Then I broke out Mighty Mo!

I selected this palette because it is very descriptive.

On the left side of the vent tubing you can actually see where the warm air is blowing onto the shingles above as the sheathing is warm.

So the vent is blowing air outdoors.

But on the right side it looks like air may be leaking into the attic.  But if there is a clog it might not be much of one because air is surely blowing out.

Does the image indicate a loose connection of the tubing to the hood?  Perhaps.  The warm air seems to be blowing a distance toward the right.  This point is about 30' from the dryer, so 98F is pretty warm I guess.

But is it clogged?  That is hard to know!

My recommendation:  while very descriptive, a thermal image in this case was not definitive.  It is interesting, and does show a pattern.  The house is 10 years old, so this may be a leak in the connection at the roof sheathing.  In speaking with the seller it was learned that there was a severe clog, and all of the vent tubing was replaced from the dryer to the roof.  That would account for the stains.  As to the leaking air?  Perhaps a loose connection.  Is it a problem?  Likely not unless it pops off.



Jay Markanich Real Estate Inspections, LLC  

Based in Bristow, serving all of Northern Virginia.

Office (703) 330-6388   Cell (703) 585-7560


Comment balloon 16 commentsJay Markanich • February 27 2016 02:49AM
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