(HVAC) Flex duct used for Vent Exhaust duct???

oodssoo

It just seems as adequate of material for the use to transfer air volume through the house. Though it is logical and does not seem harmful/risky to do, I would still like to get your input on this proposition (kitchen stove/cooking exhaust).

Any input would be helpful of course. I am mainly looking for any thing (if any) having to do with the code requirement against this idea, health related problems, and any experience by anyone other than me...

Thank you in advance.

oodssoo

GBrackins

what is it you are venting?

__________________
Gary

"You get what you pay for, and sometimes free costs more!"

rockys

I dont wana jack your thread, but I have the same question... If I was venting a bathroom that has a shower (steam as an issue)... Is there an issue with using standard insulated hvac ducting?

hand drive

kitchen ducting in my experience has always been metal ducting all the way from the air intake vent to the exhaust vent, heat can get built up in the duct line and flex duct would have plastic as the first membrane for the hot air to come in contact with..

ktkelly

It's very common to use flex duct for bathroom venting and dryer venting, so I would suspect the using the same flex duct for a kitchen vent wouldn't involve any more moisture or heat.

I see no reason that it wouldn't work just fine..

GBrackins

one would need to determine the manufacturer's requirements for venting of their products. see the manual that came with the product or check online.per the 2009 International Residential Code (your code may differ):

M1502.4 Dryer exhaust ducts. Dryer exhaust ducts shall conform to the requirements of Sections M1502.4.1 through M1502.4.6.

M1502.4.1 Material and size. Exhaust ducts shall have a smooth interior finish and shall be constructed of metal a minimum 0.016-inch (0.4 mm) thick. The exhaust duct size shall be 4 inches (102 mm) nominal in diameter.

SECTION M1503 RANGE HOODS

M1503.1 General. Range hoods shall discharge to the outdoors through a single-wall duct. The duct serving the hood shall have a smooth interior surface, shall be air tight and shall be equipped with a backdraft damper. 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 installation 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. Single-wall ducts serving range hoods shall be constructed of galvanized steel, stainless steel or copper.

I certainly would not use flexible insulated air conditioning duct for venting of clothes dryers, range hoods or bathroom exhaust vents.

__________________
Gary

"You get what you pay for, and sometimes free costs more!"

oodssoo

Thanks...

Now the next (similar) question... What about for drier vent material and code requirement?

GBrackins

code requirement for dryer vent shown in my post ....

you can use dryer vent flex duct, but I'd recommend using 4" or 6" straight tube with elbows. do not use plastic vent.

http://publicecodes.cyberregs.com/ic..._15_sec002.htm for information on dryer vent

see code for maximum length (25') and deductions taken for elbows based upon diameter of vent.

__________________
Gary

"You get what you pay for, and sometimes free costs more!"

gracieblk

I'm not an expert, but I can "second" that for kitchen venting, a solid (rigid) duct is recommended.

The company I got my range hood from gave me an in-depth explanation as to why flexible ducting is a bad idea.

1.) Flex ducting buried in the wall / ceiling will most likely be against building code in many areas (so you'll fail inspection). It's OK to have it exposed in a room, like a dryer vent, but NOT OK to have it inside walls.
2.) Flex ducting vibrates and makes additional noise, and you do not want the range hood to be noisy.
3.) Since flex ducts have "zigzag" sides, the air flow will "catch" on them and reduce performance. Meanwhile, a solid duct will give you smooth airflow.
4.) Flex duct may break or crack eventually, spilling moist & greasy air inside a confined space. Potential mold and bacteria growth issues, baaaad idea.

So, besides code requirements, there are some VERY good reasons not to go with flex.

I made sure that my contractor used a solid metal duct for the kitchen hood, as per the range hood company's recommendations, and I have to say I'm very happy with the final result.