Dryer Vent Safety

By
Home Inspector with Der Hous Inspector
M1502.6 Duct length. The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7,620 mm) from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each 45-degree (0.8 rad) bend, and 5 feet (1,524 mm) for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.

This means that vents should also be as straight as possible and cannot be longer than 25 feet. Any 90-degree turns in the vent reduce this 25-foot number by 5 feet, since these turns restrict airflow.
A couple of exceptions exist:

  1. The IRC will defer to the manufacturer's instruction, so if the manufacturer's recommendation permits a longer exhaust vent, that's acceptable. An inspector probably won't have the manufacturer's recommendations, and even if they do, confirming compliance with them exceeds the scope of a General Home Inspection.
  2. The IRC will allow large radius bends to be installed to reduce restrictions at turns, but confirming compliance requires performing engineering calculation in accordance with the ASHRAE Fundamentals Handbook, which definitely lies beyond the scope of a General Home Inspection!
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Re-Blogged 2 times:

Re-Blogged By Re-Blogged At
  1. Roy Kelley 02/18/2010 05:49 AM
  2. Yvette Chisholm 02/18/2010 05:58 AM
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Rainmaker
189,711
Darren Revell
Keller Williams Realty Temecula Valley - Temecula, CA

Thanks for the info... Never knew that the bends made a difference.  Oh, the Lions and the Riders meet up again in a few months.. Good times...

Feb 11, 2010 04:44 PM #1
Anonymous
Anonymous
Anonymous

I find some pretty interesting dryer runs in older homes here, such as this beauty:

Interesting dryer duct

Feb 16, 2010 10:04 AM #2
Rainer
49,330
Der Hous Inspector LLC
Der Hous Inspector - Moose Jaw, SK
Not just a Visual Inspection.

Thats some picture Russel,

Darren are you a Riders fan or a Lions fan?

Feb 16, 2010 10:44 AM #3
Rainmaker
211,587
Yvette Chisholm
Long & Foster Real Estate, Inc. - Rockville, MD
Associate Broker - Rockville, MD 301-758-9500

Thanks for the information!  Very helpful...I am going to reblog this.

Feb 18, 2010 05:55 AM #4
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Rainer
49,330

Der Hous Inspector LLC

Not just a Visual Inspection.
Is your Inspector giving you the whole Picture?
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