Clothes Dryer Vent Safety & Installation Tips
Clothes Dryer Exhaust System Venting Materials
Clothes Dryer Vent Safety. The minimum-allowed clothes dryer exhaust vent piping diameter for all installations is 4″.
Plastic Flex Duct is a flexible dryer vent duct with a spring wire covered with plastic.
I’ve seen this material used in older homes as “dryer vent ducting” . Plastic should not be used!
There’s a variety of materials that I’ve observed that are bad or even be a safety concern in your home.
Like: Reducers, PVC pipe, Excessive Length or Turns, Chicken Wire
- Reducers like 4″ to 3″ will cause a 25% or more reduction in airflow, and increase cost of operations.
- PVC can build up a static discharge and ignite the lint, causing a fire!
- Long Ductwork will reduce airflow, and be the cause of long dryer times.
- 90° Turns in clothes dryer pipes creates turbulence reducing efficiency and are the place lint collects!
- Chicken Wire is often used to block birds or squirrels. They also trap lint!
Foil Flex Duct clothes dryer vent transition duct materials come in two types.
- Gas Dryer Foil Flex should only be used as transition between wall and dryer.
- Bathroom Foil Flex should not be used with clothes dryers.
Advantages of Using Metal Dryer Vent Ducts
The Lint King Inc. prefers rigid-solid metal dryer vent ducting where possible for Clothes Dryer Vent Safety. TLK’s next choice is semi-rigid metal pipe. I found that this material is easily dented or crushed breaking open and leaking lint and other gases into your home’s interior.
Bottom line is that having smooth interior surface vents provide advantages for clothes dryer efficiency and fewer repairs. How they help…
- Provide better air flow, smoother internal surface
- Decrease accumulation of lint debris inside the duct system
- Reduce drying time and operating costs
- Fire safe due to solid metal and foil taped joints
- Less likely to be punctured and leak back into room
- Maintenance is easier and cleaning doesn’t damage plastic or foil
Clothes Dryer & Dryer Vent Temperatures
Wow! Did you know that heat builds up with a clogged dryer airway! Check out this article on CLOTHES DRYER TEMPERATURES that illustrates the various temperatures found inside your clothes dryers.
Inside a clothes dryer are parts like; motor, controler, drum, heater, and many safety features. Modern clothes dryers have sensors for both normal safe operation and during unsafe conditions that risk a dryer fire in your home!
High temperatures will cause an equipment failure, such as a humidity sensor, temperature control system, blower motor, fan, or timer control unit!
A table of the normal and unsafe clothes dryer operating temperatures.
Modern Clothes Dryer Temperatures
Clothes Dryer Vent Safety
|Gas and Electric
Cycles & Functions
|Normal / Safe Clothes Dryer Temperature||Abnormal / Unsafe Clothes Dryer Temperature|
|Air inlet to the clothes dryer
into the heating element
|64 °F to 75 °F|
|Operating temperature for an
clothes dryer heat element
|Air temperature entering the drum||175 °F|
|Air temperature inside the drum||125-135 °F||> 392 °F|
|Air temperatures in the exhaust vent||125-135 °F||> 392 °F|
|~Exhaust temperatures at an
interior exterior wall
|113-130 °F||> 392 °F|
|~Clothes dryer exhaust vent outlet interior surface temperature||100-145 °F||> 392 °F|
|Thermochemical decomposition temperature range||200-300 °F|
|The safe operating temperature on
inside a clothes dryer cabinet
|<= 392 °F||> 392 °F|
The NFPA estimated an annual rate of 16,800 fires, 51 deaths, 380 injuries & property loss of about $236 million – NFPA Annual Fire Loss Report for Home Fires Involving Clothes Dryers.
Maximum Clothes Dryer Vent Lengths and Turns
Keep the vent duct as short and straight as possible for maximum clothes dryer vent safety
Industry standards recommend that the maximum “concealed” rigid metal ducted clothes dryer vent length be no more than 25 feet.
That effective length of a dryer duct with bends gets increased by 2.5 feet for each 45° turn and 5 feet for each 90 degree bend.
If a clothes dryer vent is 25 feet in length and has three 90º elbows, which is very common, it would have an effective length of 25 + (3×5) = 40 feet!
Dryer vent duct routing mistakes
Clothes dryer exhaust vents should be directed to the building exterior. Do not vent the clothes dryer indoors nor into an attic, crawl space, or other enclosed area.
Get the Clothes Moisture & Lint Outside Away From the Interior of Your Home
Manufacturer of clothes dryer emphasized that the venting needs to carry the moist air all the way to the building’s outside. Did you know that homeowners that use a dryer vent’s air to increase the building indoor humidity level are…
… In ViolatIon of Local Code and Manufacturer’s Instructions !
Do not vent directly into the building’s attic, basement, crawl space, or any of the building’s interior walls.
This will lead to moisture condensation on surfaces like the building insulation, building framing members, walls, floors, or attics. In these locations adding clothes dryer laundry moisture will certainly encourage mold growth.
Even if the dryer exhaust vent does extend to the outdoors… an improperly installed, crushed, or disconnected dryer vent can leak lint and moisture. Even carbon monoxide (CO) can be leak into the building.
Rusty or brown leak stains in ceilings may be traced to water leakage from a clothes dryer vent in the ceiling!
Complete details about clothes dryer exhaust vent installation can be found in this article at Clothes Dryer Exhaust Vent Installation
Clothes Dryers that Vent into the Attic?
Don’t vent clothes dryers directly into the attic space because you’re putting moisture into the attic. Now mold growth can start on wood surfaces and the in attic’s insulation.
Clothes Dryers that Vent into the Crawl Space?
Clothes dryer vent exhaust shouldn’t be hung near screen vent opening of the crawl space. Lint will clog the crawl space vent and the damp dryer exhaust air will create mold and mildew on the crawl space ceiling.