Vent clothes dryers directly to the outdoors, except for ventless dryers equipped with a condensate drain. Use smooth metal ducting ≤ 35 feet in calculated length, supported ≤ every 12 feet. Locate duct terminus ≥ 3 feet from other openings.
Route the dryer vent horizontally to the home's outside wall. Duct work should pitch 1/4-inch per foot to the outside. This keeps moisture out of the pipe. For basement laundry areas where your ductwork will run vertically to the outside wall, you may need to use 90-degree elbows.
Dryer venting tips and practices
Flexible transition hose between the dryer and the wall outlet should be either the foil type or the aluminum flexible duct (most preferred). Do not use the plastic or vinyl. Concealed ducting must be rigid metal (galvanized or aluminum) duct.
M1502.
According to the M1502. 5 code, the construction of a dryer duct has to be a minimum of 0.4 mm thick with a smooth interior. This means ribbed vents are no longer being used. Additionally, all duct joints must point in the direction of airflow.
Dryer vents should be sealed with foil tape as they can withstand the high temperatures encountered during machine use. Other tapes, even duct tape, are susceptible to failure under the extreme heat. Non-foil tape can also catch on fire.
The flexible nature and expandable configuration allow most installs to occur without any modification to the duct or the wall penetration. A pair of jumbo zip ties and you're good to go…at least for a few months until all of the internal bumps and ridges begin to clog with lint.
Although dirty, this break allows heat and moisture to escape and limits your immediate risk of a dryer fire. PVC piping will not do this which leads to water pooling and severe clogs. These clogs will cause your dryer to overheat and become a potential hazard.
A summary of the typical codes relating the dryer venting is as follows: Dryer vent systems shall be independent of all other systems and shall convey the moisture to the outdoors. Terminations shall be a minimum of three feet from property line and 12" above the ground and not exhibit any type of screen.
Per the requirements of the International Residential Code, Section M1502 (2009-2021 IRC), the clothes dryer exhaust duct should be a rigid or semi-rigid metal duct made of galvanized steel or galvanized aluminum with a smooth interior finish and a duct diameter of 4 inches.
In situations where outdoor venting is not an available option, the vent bucket serves as an efficient indoor solution. It collects lint and moisture, ensuring they do not disperse throughout your living area. It is particularly convenient for apartments or temporary setups.
Some dryer vent installations also have an external lint trap, which is also known as a secondary dryer lint trap or a 4″ In-Line Dryer Lint Trap.
Vent elbows are available which is designed to turn 90° in a limited space without restricting the flow of exhaust air. Restrictions should be noted in the inspector's report. Airflow restrictions are a potential fire hazard.
Ideally, your dryer should have exhaust vents that lead outside to keep your laundry area clean and less humid. The most common place to vent your dryer is horizontally through the exterior wall near the dryer, which is the ideal placement.
Keep flammable materials and vapors, such as gasoline, away from the dryer. Place dryer at least 18 inches above the floor for a garage installation. Failure to do so can result in death, explosion or fire.
Codes and Standards
In the United States, most home inspectors refer to the International Residential Code (IRC) M1502 for dryer venting. However, some states may have additional regulations. The International Mechanical Code (IMC) 504 also includes extensive clothes dryer requirements.
I've only seen and used 4 inch dryer vent piping. Various construction platforms call out 4 inch for dryer venting, 3 inch for ceiling fans (bathroom exhaust).
Improperly installed dryer vents can lead to airflow restrictions, longer drying times, increased energy consumption, and overheating. Additionally, they can cause lint and moisture to escape into your home, leading to mold growth and potential fire hazards.
You can use a 4-inch flexible aluminum foil duct that is UL 2158A listed and marked for safe dryer venting. Look for a product that is constructed from heavy duty, fire resistant aluminum foil with a high density, corrosion resistant wire helix. Remember that only ducts 8 feet or less can be UL listed and marked.
One of the most serious consequences of inadequate dryer venting is the increased risk of a house fire. When lint accumulates in the vent system due to poor ventilation, it can easily ignite and cause a fire. Regular dryer vent cleaning and maintenance are essential to prevent this serious safety hazard.
Dryer Vent Locations
The best place is usually an exterior wall, which allows the duct type to be as straight and short as possible, minimizing lint buildup and reducing the fire hazard.
Rigid Metal Ducting: Rigid metal ducting, such as aluminum or galvanized steel, is widely considered the gold standard for dryer vent systems. These materials are non-combustible and can withstand high temperatures, reducing the risk of fires.
It's best to choose a material such as rigid metal for your dryer vent hose, which is much less flammable than plastic or aluminum. If you install your dryer yourself, follow the instructions from the manufacturer before installing the dryer vent hose.