Changing duct size

11 years ago

I have honestly searched but couldn't find an answer to this question.

If I have a 6" round duct in the kitchen ceiling that is transitioned to a 10" duct in the attic (and is 10" all the way going to the roof), how hard would it be to make it all 10", provided that the attic is totally accessible and there are no obstacles?

And I don't mean using reducers or transitioners, but physically changing the duct size.

Isn't it just cutting a larger hole and replacing that section of the duct pipe between the ceiling and the point where it is already 10"?

How much it would cost in your area? Again, assuming no obstacles.

And yes, I know that YMMV.

TIA!

Comments (7)

snoonyb
11 years ago
How about-------What is the purpose of the ducting?
eleena
Original Author
11 years ago
Oh, sorry.

It is for a range hood.
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User
11 years ago
How are you going to attach the 10" duct to the 6" fitting on the range hood?

Point being is the range hood and exhaust fan are designed for 6" ducting. Having the ducting connected to the larger diameter duct means the air flow is reduced and that means moisture/airborn grease may be collecting on the ibside of the 10" duct material.

Better replace the 10" with 6".
eleena
Original Author
11 years ago
But the hood I want to get requires a 10" duct.

Many of new hoods with larger CFM require an 8" or a 10" duct.
renovator8
11 years ago
If the hood requires a 10" exhaust duct you need to change the existing duct to 10". I don't see where the difficulty is.

The cost is entirely dependent on the existing conditions of which we know almost nothing.

You need to hire someone knows how to do this without creating a fire hazard.
eleena
Original Author
11 years ago
Yes, I KNOW that I need to hire someone. I am not going to do it myself.

However, because our remodel got delayed, the guy who was supposed to do it is currently unavailable on another job. Ordering a custom hood takes several weeks. If the cost of changing the duct size is too high, I will consider hoods with 6" ducting. There are some nice ones, like Futuro, in that size too.

I am not asking for an exact quote, just a ballpark, assuming everything being "uncomplicated", like having full access. What conditions do I need to specify? I don't know what's involved in changing the ducting in one location (not the entire run).
User
11 years ago
Ok, my initial advice is not applicable since the new hood is designed for 10" duct.

If the initial installer is not available, Id recommend trying to find an HVAC company/person to install regular metal smooth HVAC ducting.

That is much better than the flex plastic or even flex metal ducting. The flex ducting provides a lot of bumps/ridges to attract moisture/grease that can condense as it cools.