Significant changes to the 2018 International Mechanical Code

The 2018 Significant Changes guides are available for the International Building, Residential, Fire, Plumbing, Mechanical and Fuel Gas Codes. This valuable series can help any code user save time by zeroing in on the most critical changes in the 2018 International Codes. The Code Council’s technical experts provide summaries, analysis and graphics for these changes making them clear and easy to understand.

2018 International Mechanical Code

An addition to Section 504.4.1 (Clothes Dryer Exhaust Termination) of the 2018 International Mechanical Code now addresses the required size of dryer exhaust duct terminals.

This change is significant because the allowed length of a clothes dryer exhaust duct is based on the assumption that the exhaust terminal poses little flow resistance. Nothing in the code requires a reduction in the allowable length of the duct based on the resistance of the exhaust terminal; therefore, it was determined to be necessary to specify a minimum size terminal opening to account for the flow resistance offered by the terminal.

Dryer manufacturer’s instructions will specify the minimum opening depth for outlet hoods and this new code text further specifies a minimum terminal opening area. The minimum opening area of 12.5 square inches is equivalent to the area of a 4-inch round duct.

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