How is your inside wall hood vented???

mom2tykelJanuary 4, 2011

DH and I were having a discussion while browsing through local appliance stores and agreed we both would like a vent hood in the new kitchen to replace the OTR MW. However, we didn't agree on how it should be vented. Our range would be on an interior wall that is shared with the MBR and is about 10 feet from an exterior wall. We do have a full basement. Can you explain/tell me how your range is vented on an interior wall.


1st KD visits on 1/17

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Up through the ceiling, thru a chase in the second story, thru the attic and then out the roof.

    Bookmark   January 4, 2011 at 8:52PM
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To the side along the interior wall that the hood is on, and out the side of the house, with ducting hidden behind a soffit that will be covered by the cabinets. This only works for an under-cabinet hood with cabinets to the side of it that go all the way to the exterior wall (I hope that's clear!).

We would have preferred a chimney style for aesthetic reasons but had no way to vent one from an interior wall without putting in too much length in ducting or too many 90 degree turns in the ducting. We wanted no more than one "90" or the whole thing becomes terribly inefficient. The specs that come with each hood should tell you how many feet of straight ducting is equivalent to a "90. For ours, each 90 degree turn is equivalent to 15 feet of straight duct.

    Bookmark   January 4, 2011 at 9:05PM
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Assuming the joists run the right way: Up in the ceiling, between the joists and out the wall of the house. No soffit needed in this case. This is how the island range is vented in the house I grew up in

    Bookmark   January 4, 2011 at 9:08PM
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Mine is like palimpsest's. I told the builder to plan for it, so he made sure the joists were placed to make it work. If that hadn't been possible, the cabinetmaker would have built the boxes with reduced depth on the uppermost section so we could run the vent behind them.

    Bookmark   January 4, 2011 at 9:43PM
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Straight through the upper cabinets, through the attic and out the roof. (Cabs extend to ceiling so you can't see the duct unless you open the doors.)

    Bookmark   January 4, 2011 at 11:15PM
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Up through the upper cabinet into the ceiling. 90 degree turn to the left. Out between the joists to the side wall of the house.

    Bookmark   January 4, 2011 at 11:56PM
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Thank you for your replies. My husband mentioned having it vent into the basement...yuck! He said it is far better than what the OTR MW does now. I was hoping we could vent up the wall and take a sharp left to the outside. I don't think going up past the 2nd floor to the roof would be in the budget...we have no idea what is in the walls upstairs.

I will present this question to the designer/contractors we have coming to visit.

1st KD visits on 1/17

    Bookmark   January 5, 2011 at 10:28AM
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Mine goes through the upper cabinet

There is a wood cover that hides it (there will be a glass door with three panels, I have a clock that just fits in front of the wood panel).

Then it goes up through the roof - this is about as easy as it gets for an install through the roof.

This was taken while we had the ceiling open in the adjacent room. After we moved the kitchen wall in, the pipe is about straight up and down.

The lower black vent is the one for the range hood. Since we knew about where it was going to eventually be, we installed the hood part when we fixed the roof back in 2004.

    Bookmark   January 5, 2011 at 10:47AM
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My exhaust ductwork was already in place when I re-did my kitchen. The duct goes up through the cabinet above it, into the ceiling, then makes a 90-degree turn to the right, and goes about 7' to the outside of the house. You are right that going down through the basement wouldn't be such a good idea. It's simple physics that smoke and grease rise up, and exhausting them downward just makes the task unnecessarily harder. Also, the longer the duct, and the more turns the duct makes, the less effective is the exhaust, or you'll have to buy a higher-cfm hood to make up for all that length and number of turns.

One thing to keep in mind--and I know regulars on this forum are likely tired of hearing me say this--I should have changed the duct when I had the chance when the walls were open during my reno. By "change", I mean enlarge. The existing duct is 6" diameter. I should have changed it to 8" diameter. The 6" size is too small, which creates significantly more noise, and cuts down significantly on the hood's effectiveness and efficiency. Furthermore, most hoods on the market with 600 or more cfms require an 8" duct, although you can find some at 600 cfms that are OK with a 6" duct, but those are harder to find. EVERY time I use my hood, and I have the loud noise, and so-so exhaust, I regret that I didn't install an 8" diameter duct when I had the chance.

    Bookmark   January 5, 2011 at 12:36PM
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Some hoods say right in the manuals that you cannot vent Down because of the convolutions you are putting in the piping: essentially a 180 + . Its essentially turning a conventional vent hood into a downdraft albeit with overhead capture. My almost straight up vent pipe in one kitchen had some natural chimney effect even when the hood was turned off (it probably wasn't dampered well.) You are trying to push hot air down with a downdraft which is going against physics and why they have to work harder and are less effective.

    Bookmark   January 5, 2011 at 12:56PM
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Mine goes up to the floor joists, makes a 90 degree turn, goes about 10-12 feet and has a 45 degree turn to the roof where the blower is. We thought we'd try going straight up, but the second floor bathroom and closet didn't sit quite where we thought they would. Anyway, this is working well. We were starting over with ventilation, so we went with a 10" duct to minimize the impact of the turns and the air noise. It was the most we could fit between the joists. We couldn't fit a silencer without being able to get to the attic, but the larger duct seems to have helped. My 1200 cfm fan (rarely run at full speed) is quieter than the poor downdraft we had -- probably a 6 inch duct.

    Bookmark   January 5, 2011 at 12:57PM
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Great information and pictures. Knowing the size of the duct helps to lessen the noise is helpful as well as don't send the air down.

Thank you!

    Bookmark   January 5, 2011 at 2:30PM
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We've just installed a large 600--1200 cfm wall-mounted hood over our range: the exposed round duct rises up out the top of the hood (no overhead cabinets) to the ceiling and empties into a plenum/preinstalled square duct at a 90 degree angle -- that duct then runs between joists 18' to a vent on the rear wall of the house, over the living room ceiling. We were lucky that the joists ran the right way to do this, and the position of the round duct on the custom hood was determined by the location of the one bay that would accommodate the horizontal duct to the outside! That 18' run after a 90 degree turn is pretty long, right? but the duct seems to draw extremely well even at 600 cfm. Tonight for the first time we seared steak without filling the house with smoke and smells.


    Bookmark   January 5, 2011 at 8:29PM
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Ours goes up through cupboard and into attic then up to almost the peak of the roof before it exits house.

We are experiencing some issues with snow melt this year on roof in area of duct, but this is an extraordinary year for snow. Most years there would not be this problem. Because we've insultated the pipe so well through the attic and walls, there is heat exhausted out the top. Our old vent went merely into the attic. Worked well for dissipating heat, but was terrible for moisture in attic and ruined the ceiling paint in area surrounding vent. That's illegal now anyway.

Dig about for my tale of woe regarding venting laterally into a walkpath--on a different thread. Moral of story: Be sure you check code!

    Bookmark   January 6, 2011 at 12:31AM
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If you're just venting into the basement, I would not. You can go through the basement to the outside (if it's possible w/your vent & duct work), but don't just vent it into the basement.

Ours goes out the back into the wall behind the hood and then up the wall to the ceiling. It then runs across the kitchen to the exterior wall b/w the joists in the space b/w the first and second floors. It then turns down then out...kind of like a "Z" with a vertical stem. Yes, it's more turns than I would have liked, but it was the "lesser of two evils" at that point. (The other "evil" was a recirculating way did I want all that smoke, odors, grease, steam, etc. vented back into my home!)

    Bookmark   January 6, 2011 at 1:30AM
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Our cooktop wall is adjacent to the garage, so the ductwork goes straight back into the garage, takes a 90 degree turn and then vents to the outside wall. The ductwork in the garage is covered up by a drywall soffit. The remodeling company planned on running the ductwork inside the wall, but the plumbing from the master bath comes down in the corner where the outside wall and cooktop wall meet. The garage soffit was the easiest solution.

    Bookmark   January 6, 2011 at 6:46AM
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