Dryer exhaust vent - InspectionNews

RobertSmith · #1 (**permalink**) 08-19-2007, 08:48 AM

..........

John Arnold · #2 (**permalink**) 08-19-2007, 09:47 AM

That looks like the foil type, not plastic. I have seen foil that is UL listed for dryers. Not ideal, for sure.

Jerry McCarthy · #3 (**permalink**) 08-19-2007, 10:37 AM

OK for its location (exposed) but once it enters the wall until it exits the home, smooth non-combustible duct material only. 2006 UMC 905.4

David Banks · #4 (**permalink**) 08-19-2007, 10:39 AM

Check your local codes. Plastic not allowed in MA. Foil is.
I put something like this in my report.
DRYER VENTING:
: Suggest rigid metal vent pipe (Aluminum or galvanized) for dryer. Vents should not be connected with sheet metal screws.
:Foil aluminum or plastic type not recommended as these can catch lint. Potential fire hazard issue.
: Flexible transition ducts shall not be concealed within construction.

Jerry Peck · #5 (**permalink**) 08-19-2007, 12:38 PM

Quote:

Originally Posted by John Arnold

That looks like the foil type, not plastic. I have seen foil that is UL listed for dryers. Not ideal, for sure.

Quote:

Originally Posted by Jerry McCarthy

OK for its location (exposed) but once it enters the wall until it exits the home, smooth non-combustible duct material only. 2006 UMC 905.4

Neither the white plastic nor those aluminized mylar "foil" (which are still plastic) are approved for use with dryers.

The foil ones have a UL listing, for air ducts, not for dryers, and, no manufacturer of dryers show their use is allowed in their manufacturer's installation instructions - at least none that I've read to date.

They all want rigid metal dryer ducts and rigid metal dryer connectors (those short pieces are dryer connectors), and, if rigid metal dryer connectors are not possible, then flexible metal (made entirely of aluminum and are not "foil") dryer connectors are allowed.

Thus, those foil ones need to re written up for replacement with either a rigid metal (preferred) or flexible metal (second choice) dryer connector.

John Arnold · #6 (**permalink**) 08-19-2007, 12:43 PM

Quote:

Originally Posted by Jerry Peck

The foil ones have a UL listing, for air ducts, not for dryers,

I'll look again when I'm in the Big Orange Box, but I could have sworn I saw foil ones UL listed for dryers.

Jerry Peck · #7 (**permalink**) 08-19-2007, 12:59 PM

Quote:

Originally Posted by John Arnold

I'll look again when I'm in the Big Orange Box, but I could have sworn I saw foil ones UL listed for dryers.

Even if you find one that is, the dryer manufacturer states DO NOT USE them, and, thus, they are not allowed to be used.

Read the dryer instructions and look in the WARING! and RISK OF FIRE! sections.

Bob Harper · #8 (**permalink**) 08-19-2007, 01:59 PM

Many mfrs such as Maytag used to state in their manuals if combustible venting used ,it voided the warranty of the appliance.

While the code allows limited use of corrugated metal hose, it does no good if the duct is crushed or mishapened to where it blocks flow. In the photo, you see a flex duct that was not trimmed to length. This can easily block reducing airflow which can overheat the unit, cause a fire, premature component failure and lint blowback into the guts of the machine. Don't rely on snap switches alone for safety-they are designed, mfd. and installed by man, thus prone to failure.

imported_John Smith · #9 (**permalink**) 08-19-2007, 04:52 PM

Our local radio host (Tom Tynan) that seems to have a chip on his shoulder for home inspectors told a caller this morning that it was acceptable to use the flexible ducting through out the attic. Surely this guys not wrong. He's on the radio.

Jerry McCarthy · #10 (**permalink**) 08-19-2007, 06:15 PM

Should have taken the time to post the appropriate codes rather than shoot from the lip.

2006 Uniform Mechanical Code
905.4 Exhaust Ducts for Type 1 Clothes Dryers.
(A) A clothes dryer exhaust duct shall not be connected into any vent connector, gas vent, chimney, crawl space, attic, or other similar concealed space.
(B) Ducts for exhausting clothes dryers shall not be assembled with screws or other fastening means that extend into the duct and that would catch lint and reduce the efficiency of the exhaust system.
(C) Exhaust ducts shall be constructed of rigid metallic material. Transition ducts used to connect the dryer to the exhaust duct shall be listed for that application or installed in accordance with the clothes dryer manufacturer's installation instructions. [NFPA 54:9.4.4]

2006 IRC:
SECTION M1502
CLOTHES DRYER EXHAUST
M1502.1 General. Dryer exhaust systems shall be independent of all other systems, and shall convey the moisture to the outdoors.
Exception: This section shall not apply to listed and labeled condensing (ductless) clothes dryers.
M1502.2 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. Exhaust ducts shall terminate not less than 3 feet (914 mm) in any direction from openings into buildings. .Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination
M1502.3 Duct size. The diameter of the exhaust duct shall be as required by the clothes dryer’s listing and the manufacturer’s installation instructions.
M1502.4 Transition ducts. Transition ducts shall not be concealed within construction. Flexible transition ducts used to connect the dryer to the exhaust duct system shall be limited to single lengths, not to exceed 8 feet (2438 mm) and shall be listed and labeled in accordance with UL 2158A.
M1502.5 Duct construction. Exhaust ducts shall be constructed of minimum 0.016-inch-thick (0.4 mm) rigid metal ducts, having smooth interior surfaces with joints running in the direction of air flow. Exhaust ducts shall not be connected with sheet-metal screws or fastening means which extend into the duct.
M1502.6 Duct length. The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7620 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 (1524 mm) for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.
Exceptions:
1. Where the make and model of the clothes dryer to be installed is known and the manufacturer’s installation instructions for the dryer are provided to the building official, the maximum length of the exhaust duct,

Photo of acceptable transition of clothes dryer duct to rigid metal duct passing into wall framing.

Jerry Peck · #11 (**permalink**) 08-19-2007, 06:19 PM

Quote:

Originally Posted by Jerry McCarthy

Photo of acceptable transition of clothes dryer duct to rigid metal duct passing into wall framing.

Correct.

That is the correct stuff if you are using flexible dryer connector instead of rigid metal dryer connector (referred to in those code references as 'transition duct'.)

That foil stuff ... that's a no-no.

Matt Fellman · #12 (**permalink**) 08-23-2007, 12:56 AM

This seems like one of those 'no enforcement possible' codes.... how many times is there a dryer installed when the house is given its final occupancy?

It probably explains why the majority of the ones we see in use are wrong according to the code. I'm sure 9 of 10 people that walk into HD and ask the kid for a dryer vent are given the wrong one.

BARRY ADAIR · #13 (**permalink**) 08-23-2007, 04:42 PM

Quote:

Originally Posted by Matt Fellman

This seems like one of those 'no enforcement possible' codes.... how many times is there a dryer installed when the house is given its final occupancy?

It probably explains why the majority of the ones we see in use are wrong according to the code. I'm sure 9 of 10 people that walk into HD and ask the kid for a dryer vent are given the wrong one.

That is why I keep posting this article and have the link embedded in all of my reports

Dryer Venting Guidelines - How to avoid dryer fire hazards

None of use real knows what takes place upon possession transfer, in most cases.

Joseph Michalski · #14 (**permalink**) 08-23-2007, 05:07 PM

Good article, Barry - I think I will begin to add the link in my helpful hints as well.

Also, thank you for the clear picture of the appropriate type of flex vent (whoever posted it). Often a picture speaks far more clearly to the client than I can.