Joe- thanks for the detailed information!

Unfortunately, though we do a lot of stir frying and cooking with aromatic spices, we are limited to a lower cfm by both budget and space. Since we must go up through the walls, we will need to use 10x3.5" rectangular duct, which has a smaller area than the 8" duct which seems to be required for the more powerful units.

I've been looking at this 440 CFM unit, though notice that This 600 CFM unit can be used with 10x3.5" rectangular duct. It's a bit above budget though!

Fortunately, only one 90 degree turn will likely be required if we are able to go up through the walls, possibly with a little minor angling in the attic to avoid the rafters.

IF noise is an issue, how about a duct with a remote fan?

You can up the cfm without adding noise, and since you will be removing wall covering to install ductwork, you can use a rectangular duct rather than a round 4" pipe. A remote blower sounds daunting, but is not. The range hood (hood only, no fan or motor -- commonly called a "hood insert") captures the exhaust and the fan, usually installed in the attic, pulls it up and then out through the roof (or gable).

This video is about one particular brand, but the same principles apply to any brand.

Those remote fans sure look great, but from what I can see, they are out of our price range. :(

remote fans all look for 10" ducts generally. Plus they get pretty expensive.

There are definitely 600CFM ones that will work with 3 1/4" x 10" ducting. The broan is one of them, and I will have to look but I believe the Zephyr Tempest I will work as well. That's 650CFM. I would look more at it, but that shoud get you started for sure.

You really need a 650 CFM if you can swing it. You won't be happy with less, and that 90 degree angle is going to cut down a lot. I vented my hood up through the 2nd floor, through the shallow attic, and out the roof and it's been great. It was a straight shot, up through the 2nd floor furnace closet. Before, it had a 90 degree angle and came out to close to the back door and 2nd story windows - cooking odors everywhere!

Check your stud widths in the wall. You might be able to go up to 3.5"x14". And I would go for the larger blower with the two story distance and flow resistance of a rectangular vent.

hafamily5:

You're not going to get a lot of air through an 1 1/4" hole when you bore your top and sill plates.

Joe is onto the real issue, sure you can fit the duct into the wall space, but you cannot make the same size openings in the sill plates. Is the space in the bathroom above cabinet space such that you could lose some cabinet depth by putting the duct inside the sill plate and adding a false wall in front of it? Or can the duct be run somewhere else and a cover for the duct be added such that it looks like an extra beam or decoration?

Is make up air required if over 400CFM's. I thought so but haven't seen this mentioned here.

Re cutting through the sill plate, I believe code allows for it if the joists are then reinforced by strong metal straps. (See HERE, pg. 9).

Practigal- unfortunately, we can't bump the wall out if we go up, because it would block a doorway on the second floor, and sadly, both outside walls of the kitchen have either HVAC units on the ground nearby and intake vents, or French doors that would be too close to the new range hood exhaust vent.

Silken- I am covering my ears and can't hear you! ;)

Actually, I have been thinking about make-up air, and since this little project won't require a permit in our rural area, we will just open a window when using the highest setting for now. We can always add something later on if necessary (or if we sell).

I think you guys have convinced me to go with higher cfms. I'm looking at these models, since they can vent out the back: Kobe CHX79 and Miseno MH701. There's not much feedback out there about the Miseno, but I like the shape a little better.

This has been very interesting as I have the same predicament. It's not really encouraging me to rush into doing this. Fortunately I don't do much of any greasy cooking and I have a nearby external exhaust fan in my laundry room to suck out odors. The biggest concern is moisture wafting up on the cabinets but aside from sticky grime that I cleaned off from previous owners, the cabinets are in fine condition even after 15 years without external exhaust.

What I have been pondering is if I could somehow connect into that laundry duct work through the attic as I don't really need an exhaust fan in the laundry room.

My kitchen is undern a bedroom on 1st floor how will iI make an extac for. My stoves.

I have the same issue. Kitchen directly under a bedroom.

I too have a kitchen under a bedroom and the cooktop is on an inside wall. I want to convert to gas for re-sale but can’t figure out how to add the range hood.

Did you install a hood vent? Wondering how you liked it.

Hello, I am in the process of buying a home and suddenly discovered there is not a hood vent over kitchen island with the gas range top. How costly will this be to have a hood vent installed over a kitchen island with a bedroom over the kitchen?