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Dryer vent hood clearance distances to site features (C) Inspectapedia.com adapted from Whirlpool & AmanaClothes Dryer Exhaust Vent Codes

Clothes dryer exhaust vent installation, materials, requirements, model building codes & mechanical codes.

This article series describes good practices for clothes dryer vent installation, lint traps, wall vents, filters, and screens.

We include a list of clothes dryer fire safety hazards and other clothes dryer installation or maintenance mistakes that are either unsafe or that interfere with effective, economical dryer operation. We discuss types of dryer vent ducting and dryer vent doors or opening protection devices

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Clothes Dryer Exhaust Vent Codes

Dryer exhaust vent hood connects to vent duct and seals at wall.Note: Excerpts from the IRC as adapted by various muinicipalities provide publicly-accessible copies of the model codes as presented here using Texas' adoption of the IRC. Purchase a complete copy at online vendors or from the authoritative source, International Codes Council, listed just below.

IRC M1502 Ventilation, Clothes Dryer Exhaust code

User note: Code change proposals to this chapter will be considered by the IRC — Plumbing and Mechanical Code Development Committee during the 2015 (Group A) Code Development Cycle.

The air removed by every mechanical exhaust system shall be discharged to the outdoors in accordance with Section M1506.3. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.

Exception: Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.

Clothes Dryer Ventilation

Clothes dryers shall be exhausted in accordance with the manufacturer's instructions.

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.

IRC UMC M1502.2 Dryer Exhaust Duct Termination.

Dryer exhaust ducts shall conform to the requirements of Sections M1502.4.1 through M1502.4.7.

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.

Exhaust ducts shall have a smooth interior finish and be constructed of metal having a minimum thickness of 0.0157 inches (0.3950 mm) (No. 28 gage). The duct shall be 4 inches (102 mm) nominal in diameter.

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 in accordance with Section M1601.4.1 and shall be 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.

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 not greater than 8 feet (2438 mm) in length. Transition ducts shall not be concealed within construction.

Domestic dryer exhaust duct power ventilators shall conform to UL 705 for use in dryer exhaust duct systems. The dryer exhaust duct power ventilator shall be installed in accordance with the manufacturer's instructions.

See details and answers to specific questions

at CLOTHES DRYER VENT CLEARANCES & TERMINATION

IRC UMCM1502.3 Dryer Exhaust Duct size.

The diameter of the exhaust duct shall be as required by the clothes dryer’s listing and the manufacturer’s installation instructions.

IRC UMCM1502.4 Dryer Vent 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, and shall be listed and labeled in accordance with UL 2158A.

IRC UMC M1502.4.2 Dryer Vent Duct Installation.

Exhaust ducts shall be supported at intervals not to exceed 12 feet 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 in accordance with Section M1601.4.1 and shall be mechanically fastened.

Ducts shall not be joined with screws or similar fasteners that protrude more than 1/8-inch into the inside of the duct.

TABLE M1502.4.5.1 DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH

TABLE M1502.4.5.1 DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.

The size and maximum length of the exhaust duct shall be determined by the dryer manufacturer's installation instructions.

The code official shall be provided with a copy of the installation instructions for the make and model of the dryer at the concealment inspection.

In the absence of fitting equivalent length calculations from the clothes dryer manufacturer, Table M1502.4.5.1 shall be used.

The maximum length of the exhaust duct shall be determined in accordance with the manufacturer's instructions for the dryer exhaust duct power ventilator.

Where the exhaust duct equivalent length exceeds 35 feet (10 668 mm), the equivalent length of the exhaust duct shall be identified on a permanent label or tag. The label or tag shall be located within 6 feet (1829 mm) of the exhaust duct connection.

Where space for a clothes dryer is provided, an exhaust duct system shall be installed. Where the clothes dryer is not installed at the time of occupancy the exhaust duct shall be capped or plugged in the space in which it originates and identified and marked "future use."

Exception: Where a listed condensing clothes dryer is installed prior to occupancy of the structure.

Protective shield plates shall be placed where nails or screws from finish or other work are likely to penetrate the clothes dryer exhaust duct.

Shield plates shall be placed on the finished face of framing members where there is less than 11/4 inches (32 mm) between the duct and the finished face of the framing member.

Protective shield plates shall be constructed of steel, shall have a minimum thickness of 0.062-inch (1.6 mm) and shall extend not less than 2 inches (51 mm) above sole plates and below top plates.

IRC UMC M1502.6 Dryer Exhaust Duct Length.

The maximum allowable exhaust duct length shall be determined by one of the methods specified in Sections M1502.4.5.1 through M1502.4.5.3.

The maximum length of the exhaust duct shall be 35 feet (10 668 mm) from the connection to the transition duct from the dryer to the outlet terminal. Where fittings are used, the maximum length of the exhaust duct shall be reduced in accordance with Table M1502.4.5.1.

The maximum length of the exhaust duct does not include the transition duct.

 

Dryer Vent Manufacturer's Instructions Include Routing, Elbows, Clearances

Clothse dryer venting options recommended by GE - at InspectApedia.com

Watch out: some dryer vent installations are a bit self-contradictory. A manufacturer may recommend using elbows (presumably 90 degrees though 45s are available) of solid metal exhaust duct and may recommend against using flex-duct for dryer venting (Whirlpool as shown above and immediately-below) (we agree) ...

Clothes dryer exhuast vent details NOT recommended by GE - at Inspectapedia.com

... while other documents from the same manufacturer may show flexible dryer exhaust ducts installed and may recommend against 90 degree turns (Amana - Whirlpool 2017) - shown below.

. Dryer exhaust vent hood connects to vent duct and seals at wall.

That may be fine if the dryer flexible exhaust duct is flexible stainless steel rather than plastic (mylar) and wire ducting.


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