Author Topic: Where can I find information on dryer venting codes?  (Read 4937 times)


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Where can I find information on dryer venting codes?
« on: July 29, 2009, 11:59:45 AM »
Reply from the manufacturer:
2003 International Mechanical Code pages dealing with dryer venting:
2006 International Residential Code page dealing with dryer venting:
2009 International Mechanical Code page dealing with dryer venting:
2009 International Residential Code page dealing with dryer venting:
Note: the 2009 ICC codes have yet to be adopted but provide a good summary of the many changes that were approved during the last code review session. 

Building codes vary from region to region (with amendments) and not all of the jurisdictions follow the ICC.  In most cases they all basically include these same restrictions.  Some codes have been found to be less restrictive.  Many of them concur that the exception to the 25 foot minimum is when the appliance manufacturer's installation instructions specify maximum lengths with particular models.   In this case, the make, model and installation instructions need to be provided to the building inspector and sometimes a permanently mounted sign or placard is placed behind the dryer identifying the overall length of the exhaust duct and the respective model that the house was approved with.  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.
    Vents and duct connections shall not be connected with sheet-metal screws or fastening means which extend into the vent.
    Exhaust vents shall be equipped with a back draft damper and no screen.
    Vents shall be constructed of minimum 0.016-inch-thick (0.406 mm) rigid metal ducts, having smooth interior surfaces with joints running in the direction of air flow and having a minimum interior diameter of 4".
    Flexible duct and the respective connectors shall not be concealed within the construction.
    The maximum length of a 4-inch (102 mm) diameter exhaust vent shall not exceed 25 feet (7620 mm) from the dryer location to wall or roof termination, and shall terminate with a full opening exhaust hood.  A reduction in maximum length of 2.5 feet for each 45-degree bend and 5 feet for each 90-degree bend shall apply.  Installations where this length is exceeded shall be installed in accordance with the manufacturer's installation instructions.

2003 IMC - International Mechanical Code (section 504) and 2003 IRC - International Residential Code (section 1501). Summary: The International Mechanical Code article 504.6 stipulates the requirements for Domestic clothes dryer ducts. In brief, the maximum length of duct permitted is 25 ft. This maximum length should be reduced by 2.5 ft for each 45-degree bend and 5 ft. for each 90-degree bend. The duct should be a minimum nominal size of 4 inches in diameter and shall have a smooth interior finish.
« Last Edit: August 16, 2013, 06:04:09 AM by rickharp »
Rick Harpenau
In-O-Vate Technologies, Inc
Jupiter, FL  33477