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Dryer Vent Installation by the CODE M1502
The dryer vent exhausts moist air to the outside. The dryer has a number of requirements:
Connection. It should be connected: behind the dryer or beneath it.

It should not be restricted. Airflow restrictions are a potential fire hazard. The flexible plastic or metal dryer vents are easily twisted or crushed as they exit the dryer and enter a wall – an air restriction example. The vent elbows are designed to turn 90 ° in confined spaces without restricting the exhaust airflow.

Restrictions cause a fire hazard because, together with water vapor, the exhaust stream carries lint: flammable particles of cotton and polyester. It accumulates in the exhaust duct and, if overheated, mechanical faults can cause sparks that ignite the lint and the dryer. Soon the house bursts into flames.
For proper operation of the dryer and protection against fire, correct installation of the vent is necessary.

Dryer fires are the result of improper installation or irregular cleaning of dryer vents. If technicians followed the code during installation, there will be no such case as a fire situation.
IRC – is the code established in the US by the International Code Council (ICC). It is applied by the country’s jurisdictions and internationally.

It stipulates that anyone who intends to build, alter, repair, renovate or demolish a building or structure must obtain the required building permit.

The IRC applies to the new one- and two-family dwellings and townhouses, no taller than three stories.

It covers aspects of construction: building, plumbing, mechanical services, energy conservation, fuel gas, and electrical provisions.

We are interested in a part of the code today. Chapter 15 - Exhaust Systems. You can study the code in detail at the google request of IRC M1502
IRC - International Residential Code
Section M1502 - Clothes Dryer Exhaust
Dryers are designed and built to meet industry safety standards. The manufacturer’s installation instructions are evaluated by the agency responsible for testing the appliance and, therefore, those instructions will prescribe an installation that is consistent with the appliance installation that was tested
M1502.2 Independent exhaust systems
Dryer exhaust systems shall be independent of all other systems and shall convey the moisture to the outdoors.

Exception: doesn’t apply to listed and labeled condensing (ductless) clothes dryers.
Combustible lint and debris accumulate in the duct and heat source of the appliance. The combination of lint and heat can cause a fire. To prevent danger, the exhaust system must be independent of other systems. The exhaust systems of clothes dryers must carry moisture and combustion products outside the building.

The requirement to route the exhaust to the outside applies to both fuel and electrical appliances. The exhaust systems of clothes dryers cannot run out of or discharge into an enclosed space, such as an attic or a crawl space, regardless of whether the room is ventilated through openings to the outside.

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 backdraft damper. Screens shall not be installed at the duct termination.
In reality, the dryer vents terminate in crawl spaces or attics, where moisture accumulates in them. And moisture in ventilation is an ideal environment for mold growth, wood decay. Sometimes vents terminate under the attic ventilators, which always is a sign of the wrong installation.
M1502.4.1 Material and size.
Exhaust ducts shall have a smooth interior finish and be constructed of metal having a minimum thickness of 0.0157 inches (0.3950 mm). The duct shall be 4 inches (102 mm) nominal in diameter.
M1502.4.2 Duct installation
Exhaust ducts shall be supported at intervals not to exceed 12 feet (3658 mm) and shall be secured in place. The insert end of the duct shall extend into the adjoining duct or fitting in the direction of airflow. Exhaust duct joints shall be sealed and mechanically fastened. Ducts shall not be joined with screws or similar fasteners that protrude more than 1/8 inch (3.2 mm) into the inside of the duct.
M1502.4.3 Transition duct
Transition ducts used to connect the dryer to the exhaust duct system shall be a single length that is listed and labeled in accordance with UL 2158A. Transition ducts shall be a maximum of 8 feet (2438 mm) in length. Transition ducts shall not be concealed within construction.
Underwriters Laboratories (UL) published the Standard for Clothes Dryer Transition Duct, stating that only the UL 2158A listed transition duct should be used.
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 airflow. Exhaust ducts shall not be connected with sheet-metal screws or fastening means which extend into the duct.
This means that flexible ribbed vents should not be used. They create a fire hazard.
M1502.6 Duct length
The maximum developed length of a clothes dryer exhaust duct shall not exceed 35 feet from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced by 2.5 feet for each 45-degree (0.8 rad) bend, and 5 feet for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.
Vents should be as straight as possible and no longer than 35 feet. Any 90-degree turns of the air vent will reduce this 35-foot number by 5 feet as these turns restrict airflow.
Check if your Dryer Vent is installed properly
❌ Homeowners sometimes solve the problem on their own.
Dryer Installation or Replacement
Installation of a new Dryer Vent is needed in the cases studied above.
We check the current vent condition by the CODE M1502, clean the Dryer Heating Element and the Transition Hose + the Vent. If Installation or Replacement is needed, we proceed. This might take us up to 8h.
Installation & Re-route Dryer Venting
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Green Ductors operates in Bronx, Brooklyn, Manhattan, Queens, and Staten Island boroughs and North and Central Jersey. Call to get more info at +18887760898
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We have been cleaning air ducts, changing filters, and installing energy recovery ventilation systems in commercial units since 2015. The company's technicians are NADCA, BPI, and Energy Star certified.
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