Unfortunately, the joist runs side-to-side of the cabinet. Also, we don't really have much vertical space to play with either, 15" or so from the top of the hood, through the cabinet, to the ceiling.

I've seen a few post about cutting the joist and headering it, but not if my roof is on a truss system, right?

Why not go through the back of the cabinet and then up? Are there studs studs in the way out the back? You might need to get a new cabinet since you've already put one hole in it.

The back of the cabinet is the wall to the dining room, so can't go through there either...

Well, you've got the depth of the wall back there -- probably 3.5" and then the thickness of two pieces of drywall. You might be able to use some of that depth.

Are flexible hoses allowed in a hood vent installation?

"Are flexible hoses allowed in a hood vent installation?"

No. Rigid sheet metal only.

Is it a floor joist?
Ceiling joist?
Part of a truss?

Joists can be cut and the load sent to adjacent joists usually.

Cutting a truss is a bigger deal (and generally not allowed without an engineering stamp on the plan).

How large is your vent duct and do you have only one option (some are made to accept more than one size duct)? How far apart are your joists? Does the duct go straight up into attic space or does it have to turn?

Can you post a layout of that wall? I'm not understanding how the joist can be in front of the wall (presumable through the middle or near the front of the upper cabinets) yet also side to side of the cabinets.

This is a duct that was to go through a cabinet, right? If so you have wiggle room. A chimney style needs to be most accurate, but boxes and cabinets allow you to fudge. Rather than taking the duct down to a smaller round duct, I would look to see if a transition to a rectangular duct would allow you to fit the duct between the wall and joist without too great a reduction in air flow. Something with a flexible fit might help, but you may or may not need that if you can just get the spacing to work.

I'd cross post this over on the appliances thread. At least when I was doing my appliances and choosing a vent, I saw a lot of vent discussions there.

There is a solution but it is a structural one similar to what you would do if you wanted to install a set of attic steps. It can easily be done if you house uses typical rafter & joist framing.

Here is a link that might be useful: Installing a Pull Down Stair

Here's a picture of what I'm talking about.

The little wire sticking down in the center of the red circle is the edge of the ceiling joist. There's just a tad bit less than 6" of space from that point to the front of the cabinet.

Taken from in the attic...

The center of the red circle is just to the left of the electrical box.

Lastly.. I don't think I can cut and header the joist, since it's a truss system..

You are correct. Not the simple solution. In order to find out if cutting was even an option, with a truss system, you need a structural engineer to evaluate.

Hmmm. Not sure of other options. The only other thing I can think of is a hood that requires a smaller duct, possibly transitioning from a round to oval to round and see if that gives you the clearance. The oval would go through the ceiling and usually requires about 4" of depth for clearance. That is what is used for HVAC in 2x4 walls. However, you should consult the hood mfg and/or HVAC contractor to check sizing. You may need a 10+" oval to account for friction loss etc compared to an 8" round.

Other then those options, the only other thing I can think of is you would have to pull the cabinets forward to then get the clearance for the 8" round pipe. I'm pretty sure that is not an option at this point.

That was two ideas:

1) A hood that requires a smaller diam vent pipe.
2) Possibly using Oval Pipe to pass through the ceiling.

how much room do you have between the truss and the wall? Looks like you should be able to use a retangular vent and switch to round after you get into the attic.

You may have to go to a sheet metal shop and have them bend one up for you, but it looks to me that you should have plenty of room either going in front of the truss, or between it and the wall.

This is way easier to deal with than having a truss running perpendicular to the wall.

Have the engineering done to modify the truss.

Most of the truss companies have engineers on staff that can provide the drawings needed.

It can be hard t ID the manufacturers sometimes though.

A local PE with house experience should also be able to figure out how to mod the truss and provide the required drawings and stamp on them.

As a structural engineer, I think that transitioning to a rectangular duct is the easiest and cheapest option. Alternatively, is the wall behind load bearing? If not, cut a section of that wall out to get the duct up through there. A bit messy, but would solve your problem.

Does your actual fan have a round or rectangular exhaust?

Use rectangular duct (3.5" x 10") meant for running up inside 2x4 stud walls. You might be able to run it either in front of or behind the joist.

My hood fan (sitting in the DR waiting to be installed when I solve my own structural problems!) has a knockout on top for a 3.5x10 duct, and the wall hood connects to rectangular duct too.

Hi, there. If it just can't go in wall: Bring forward and design important-looking chimney to look GOOD (it is a hearth, after wall :). Run up dining room wall and incorporate into a built-in wall system (bookcases?, hutch?, art wall flanked by deeper storage?)

I agree with todds - you could pull the cabinet forward. My hood is 27" deep which is deeper than the other cabinets - mainly for a larger capture area. I don't think it looks weird. You may need some modifications to your cabinet or a new cabinet. It may be cheaper than the structural engineer route (We had a structural engineer on our project and he ran $150+/hr plus you now need drawings and those aren't free either).

I think other are saying to possibly use rectangular "inside" the wall behind this cabinet that is between your kitchen and DR. If that is the case, I do not think that will work or is necessary. 1st you would have to bend/transition to get that into the wall cavity. You want to eliminate bends as much as possible if you can. Not to mention you will have to take a nice chunk out of the back of the cabinet to accomplish this I would think. Not to mention I think you need something like a 5x12 rectangular duct (narrowest) for the same cubic foot of air movement for an 8" round (according to charts I have seen on the web). This will not fit in the wall.

If I am looking at the 2nd photo in your attic correctly, you are saying on the right side on the photo, above the electrical junction box, that is mounted on the joist, is where the hole is located. There is another joist behind it that is the attachment point for the DR ceiling Drywall. There is block on top of the joists connecting the two and there also appears to be horizontal blocking between those 2 joists as well. So again not sure anything could be run inside the wall. If the walls are 2x6 then you have a shot.

You said you have 6" from the edge of the joist to the front of the cabinet. So you may be able to transition something here within this space. I brought up Oval duct since it has much better/smoother flow, compared to Rectangular. Also, it would be 3 1/2" width and you should have about 3" now, from the front edge of the circle to where the wire was hanging down. Thus, you would only need another 1/2" of cabinet cut to fit the duct towards the front. But the duct would require you cutting wider.

I have to look at the local shops to see what rectangular or oval transitions are available. I did find a rectangular transition at a store, but they said the rectangular part is meant as the end piece, and you can't connect to another rectangular->round piece to transition back to round...

By the way, how are all these duct pieces attached together? screws? tape?

After looking at the local big box stores, here's what I can come up with. The oval ducts they had are all double walled, and only 4" pipes are available.

I hope I'm looking in the right section as well, it's the same stuff as the AC ducts. Let me know if you think this idea will work...

{{!gwi}}

I can't offer you any help, but I know we faced a similar situation. If the others tell you that what you have put together from the Big Box store is inadequate, I would like to suggest you get to a local HVAC store. They really had a lot more solutions for our problem. You know the kind of store I mean, right? Usually located in the bowels of H3LL in the city. They had ductwork that only an HVAC person could love.

Good luck, isn't it frustrating sometimes when you think you are making a step forward, but find yourself going backwards? Hang in there.

Second Beekeeperswife.

Also, the metal is of much better gauge and quality at HVAC supply stores.

There will be an 8" round to 8" oval at an HVAC supply store. Also, there will be other rectangular duct options as well.

If your fan has an 8" outlet, then using a reducer isn't a good idea (unless the fan is just for show). Have an HVAC guy come in and look at it.

I like the idea of bringing the cabinet forward if possible. Would likely require a lot of extra work.

HVAC guy is your best bet I would think.