Dangers of Roof Dryer vents in Orlando

As a home inspector, one of the biggest safety hazards I see daily is dryer vents.  Dryer fires are among the top ten reasons for home fires and cause more than 15,000 fires annually.  Dryer exhausting through the roof should be ducted to a special dryer roof vent without screen.   

The roof vent or louvered plenum must be equivalent to a 4 inch wall termination in regard to resistance to airflow and back-flow prevention, and should require little or no maintenance to prevent clogging.

Home built in 2013 goose-neck looks shiny and new.

2013 home inside of goose-neck vent. 

There are many issues with this type of vent.  It must be a vent that has a back-flow prevention flap and it should not have a screen.  Many of the goose-neck type of vents come with screens and are unsuitable for dryer venting.  

Goose-neck vent with screen

Goose-neck that is totally blocked.

Inoperable back-draft damper.

Goose-neck with screen was clogged.  Improper duct type.  Lint exhausted into attic damaging roof decking.

1. Dryer ducts must be at least 4 inches in diameter or at least the size of the dryer outlet. The exhaust duct must not extend into or through heating or air-conditioning ducts. The exhaust duct system should be supported and secured by mechanical fasteners. It should be insulated in non-conditioned spaces to prevent condensation.
2. The maximum length for a clothes dryer exhaust duct should not exceed 25 feet. This length should be decreased by 2.5 feet for every 45-degree bend the duct makes, and 5 feet for every 90-degree bend the duct makes.
3. The dryer exhaust ducts should be constructed of rigid metal (galvanized steel). The interior of the duct should be smooth surfaced with the joints running in the direction of the airflow. There should be no sheet-metal screws, rivets or any other fastener used to connect the duct joints. Fasteners that penetrate into the airway will catch lint and block airflow. 
4. Foil duct tape (not plastic or vinyl) should be used to secure joints. Outside termination must be equipped with a back draft damper, which prevents air, moisture and rodents from entering. The termination must not have a screen covering the exhaust outlet.

 

I have seen all of these used for dryer roof vents.  Just because they are sold at the hardware store does not make them right.

 According to the IRC:

- M1502.3 Duct termination.

- - Exhaust ducts shall terminate on the outside of the building.  Exhaust duct terminations shall be in accordance with the dryer manufacturer’s installation instructions.  If the manufacturer’s instructions do not specify a termination location, the exhaust duct shall terminate not less than 3 feet (914 mm) in any direction from openings into buildings.  Exhaust duct terminations shall be equipped with a back draft damper.  Screens shall not be installed at the duct termination.

In the opinion of this home inspector, the biggest problem I see with the roof vent is out of sight out of mind.  Each year many people die in home fires that start at the dryer.  Prevention is often easy and requires little effort.  Dryer vents should be cleaned annually but in the case of roof top vents I recommend semi-annually.  

Clothes dryers a leading cause of home fires in Orlando

Frank Carr is the Owner / Inspector at First Choice Home Inspections in Deltona, FL. Formerly in the building trades, Frank’s focus is a safe home and building FCHI. We believe that consumers have the right to expect the highest standards of thoroughness, fairness and effectiveness from their home inspector and that is exactly what we provide. Http://1homeinspector.com


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