M1501.1 OUTDOOR DISCHARGE
All systems which exhaust air from home must discharge to the outdoors (not attic, soffit, ridge vent or crawl space)
Dryer vents should be exhausted in accordance with the manufactures instructions.
M1502.2 Independant Exhaust Systems
Dryer exhaust systems should be independent of all other systems and shall convay the moisture to the outdoors.
Exectption: Condensating (ductless dryers)
M1502.3 Duct Termination
1. Terminates outside of the building
2. Exhaust terminates at least 3 feet from openings (in any direction) into building
3. Equipped with a backdraft damper
4. Screens shall not be installed at termination
M150.4.1 Material and Size
Exhausts should have a smooth interior finish and be constructed of a metal with a minimum thickness of 0.0157 inches (0.3905 mm) No. 28 gauge. The duct should ddbe four inches (102 mm) nominal diameter.
M1502.4.2 Duct Installation
1. Supported at 12’ intervals and secured
2. Duct fittings lapped in direction of air flow (shingle effect)
3. Joints sealed in accordance with M1601.4.1 (See below)
4. Joints mechanically fastened w/screws or similar (i.e. rivets)
(Screws protrude less than 1/8” into duct!)
[2018 – NEW] – Ducts shall not be deformed by wall or ceiling cavities (Example: 4” round duct cannot be installed in a 2”x4” wall cavity)
M150.4.3 Transition Ducts
Ducts used to connect the dryer to the exhaust duct system shall be single length that is listed and labeled in accordance with UL2158A. Transition ducts shall not be greater than 8 feet in length. Transition ducts can not be concealed within the construction.
M150.4.4 Dryer Exhaust Power Duct Ventilators
Domestic dryer exhaust duct power ventilators shall confirm to UL 705 for use in dryer exhaust duct systems. The dryer exhaust power ventilator shall be installed in accordance with the manufacture's instructions.
M1502.4.5 and Duct Length
[2012 – NEW] Maximum length of dryer exhaust is 35’ The maximum length does not include the transition duct.
M1502.4.5.1 Specific Lengh
Dryer Exhaust Duct Fitting Equivalent Length
(The 35’ allowable length is reduced for each bend or elbow installed)
Example: 4” duct - Reduction for 90° elbow=5’; Reduction for 45° elbow=2’6”
M1502.4.5.2 Manafactures Instructions
The size and maximum length of a dryer exhaust shall be determined in accordance with the dryer manufactures instructions.
M1502.4.5.3 Dryer Exhaust Duct Power Ventilators [2015 - NEW] – DEDPVs, (i.e. “booster fans”), are now allowed by code to increase the equivalent length of dryer duct, beyond 35’. (Adhere to manufacturer’s instructions).m
M22.214.171.124 Lenght Identification
When the exhaust duct equivalent exceeds 35 feet, the equivalent length of the exhaust duct shall be on a permanent label or tag. The label or tag shall be locked within six feet od the dryer exhaust connection.
M1504.3 EXHAUST OPENINGS (Labeled M1506.2 in the 2015IRC)
[2012 – NEW] – 1. Minimum of 3’ from property lines
2. Minimum of 3’ from operable and non-operable openings
[2018 – NEW] (deleted the words: “non-operable”)
3. Minimum of 10’ from mech. air intakes (unless 3’ above air intake)