Type 2 residential ducts to combustibles

[jack ridley]

Hello all, I have a question on type 2 duct work for a exhaust hood. What does the ductwork distance to combustibles need to be. I am running it from the kitchen on first floor through the second floor and out. It is single wall but concerned on how close I can run it next to wood framing etc. I am under the 15 irc code but cant find the code section on this? Thanks for and help or code section numbers!

 

[classicT]

If this is a single or two family dwelling under the IRC, you do not have a Type II hood. You would simply have a kitchen exhaust fan or a range hood.

If it is truly just a kitchen exhaust or a range hood, you are not dealing with hot air; therefore no separation requirement exists in the IRC. To me, it seems you may have stumbled into some knowledge of commercial range hoods, where a Type I or Type II hood is used for the removal of hot air and products of cooking (Type I is for smoke and grease; Type II is for steam, some smoke). Commercial systems do require separation due to the high-temperature air that can be exhausted, as well as the increased possibility of duct fires.

Section M1503 Range Hoods

M1503.1 General
Range hoods shall discharge to the outdoors through a duct. The duct serving the hood shall have a smooth interior surface, shall be air tight, shall be equipped with a back-draft damper and shall be independent of all other exhaust systems. Ducts serving range hoods shall not terminate in an attic or crawl space or areas inside the building.

Exception: Where installed in accordance with the manufacturer's instructions, and where mechanical or natural ventilation is otherwise provided, listed and labeled ductless range hoods shall not be required to discharge to the outdoors.
​

M1503.2 Duct Material
Ducts serving range hoods shall be constructed of galvanized steel, stainless steel or copper.

Exception: Ducts for domestic kitchen cooking appliances equipped with down-draft exhaust systems shall be permitted to be constructed of schedule 40 PVC pipe and fittings provided that the installation complies with all of the following:

1. The duct is installed under a concrete slab poured on grade.
2. The underfloor trench in which the duct is installed is completely backfilled with sand or gravel.
3. The PVC duct extends not more than 1 inch (25 mm) above the indoor concrete floor surface.
4. The PVC duct extends not more than 1 inch (25 mm) above grade outside of the building.
5. The PVC ducts are solvent cemented.

 

[jack ridley]

Got you thanks! Like I say I looked and couldnt find anything, now I know why. Thanks again!