Foil dryer ducts: code-approved?

Foil dryer transition ducts are allowed by code and by some clothes dryer manufacturers. This seems to be a frequent topic of discussion and confusion amongst home inspectors, so I'm going to shed some light on the topic. First, let's define what a dryer transition duct is.

A dryer transition duct is a flexible section of duct that can be used to connect a clothes dryer to the duct. The duct itself must consist of rigid metal.

The building code is actually silent on the type of material that may be used for a dryer transition duct. The code simply says that dryer transition ducts must be UL 2158A listed. They leave it up to UL to figure out what passes muster and what doesn't.

The building code also requires clothes dryers to be installed according to the manufacturer's installation instructions, in accordance with section 304.1 of the Minnesota Mechanical Code. This section corresponds to section M1307.1 in the 2018 IRC for people in other parts of the country.

If you stop by any home improvement store, you'll find that the products sold as dryer transitions ducts are mostly UL 2158A listed. Not all of them, but most of them. I have a bunch of comparison photos in my blog post on dryer duct safety.

Clothes dryer manufacturers are surprisingly inconsistent with their requirements for dryer transition ducts. The following manufacturers do not allow dryer transition ducts that are made from foil, regardless of whether the duct is UL2158A or not:

Kenmore and LG aren't clear. In the same manual, they gave conflicting advice. Kenmore said If a flexible metal (foil type) duct is installed, it must be of a specific type identified by the appliance manufacturer as suitable for use with clothes dryers. So they're allowed, right? Not so fast. They also go on to say Check your vent to make sure it is rigid or semi-rigid metal ducting. If your venting is plastic or flexible foil, have it replaced before using the dryer.

Similar advice is given by Samsung, Hotpoint, and GE. The crazy thing about GE, however, is how specific they get with their advice. They say the following: In special installations, it may be necessary to connect the dryer to the home exhaust vent using flexible metal (foil-type) transition duct. UL–LISTED universal flexible dryer transition duct (GE parts – PM8X73 or WX8X73) may be used ONLY in installations where rigid metal or flexible metal transition ducting cannot be used AND where a 4" diameter can be maintained throughout the entire length of the transition duct.

What's even crazier about GE is that they re-sell DryerFlex under the GE name (https://dryerflex.com/), but they don't list it as an acceptable material in their installation manuals! Let me repeat: they put their name on this superior product, but they don't allow it on their own dryers. I think my head is going to explode.

Hey dryer manufacturers, can you please all get on the same page? One standard would really be nice. Thank you.

Update 11/18/20: someone was apparently listening. I received an email today from Steven Liebson, CEO of GLV International to clear this matter up. Unbeknownst to me, they're the company that makes the product for DryerFlex. Here's the scoop: "This GE product you refer to in your video as a foil duct (polyester plus aluminum combination) above is in fact a 5-layer aluminum product. For this reason, GE defines this product as a flexible metal duct on the box and what is included in their manuals." So in other words, GE does allow this product, because they don't consider it a foil duct. They consider it a flexible metal duct. Good to know. Thank you for the information, Mr. Liebson.

The bottom line is that foil dryer ducts are allowed by code and some manufacturers. That doesn't mean they're a great product, however. To demonstrate this, I partnered up with the fine folks at Family Handyman to do a video. I'll share that in next week's blog post.