Kitchen Vent Exhaust

[skrmisz]

Hi everyone,

I am working on installing an exhaust vent for a kitchen fan, and the easiest path would be to go through the outside joist between the first and second floors. It would be a 3" hole. Could this cause a serious structural problem?
I've attached 3 related photos. Thank you in advance.

 

[Sparky617]

By outside joist do you mean the rim joist that is sitting on top of the wall? It looks like you're going parallel to the ceiling/floor joists to the outside wall. Cutting through the rim joist is not a problem.

 

[bud16415]

I’m not a pro, but I think you will be fine with a 3” hole. Always stay centered in the joist.

Welcome to the forum.

 

[skrmisz]

Yes, outside rim joist. Thank you for the response, I appreciate it.

By outside joist do you mean the rim joist that is sitting on top of the wall? It looks like you're going parallel to the ceiling/floor joists to the outside wall. Cutting through the rim joist is not a problem.

 

[skrmisz]

Thank you, I appreciate it.

I’m not a pro, but I think you will be fine with a 3” hole. Always stay centered in the joist.

Welcome to the forum.

 

[Snoonyb]

Frankly, I'd be more concerned that the volumetric efficiency of the appliance will be affected by reducing the vent size to 3", especially at that distance, and with 3, 90's.

 

[Sparky617]

Frankly, I'd be more concerned that the volumetric efficiency of the appliance will be affected by reducing the vent size to 3", especially at that distance, and with 3, 90's.

My over the range microwave has a 6" line, point taken on your concern. My powder room vent is the only 3" line I have in the house.

 

[skrmisz]

Good point, the vent does have a 6" output. I imagine it wouldn't be a good idea to put a 6" hole through the rim joist, so I'll have to think of another idea.

 

[bud16415]

Good point, the vent does have a 6" output. I imagine it wouldn't be a good idea to put a 6" hole through the rim joist, so I'll have to think of another idea.

Mock up a 4" line with the fittings you may be using and see how it draws.

 

[Sparky617]

Good point, the vent does have a 6" output. I imagine it wouldn't be a good idea to put a 6" hole through the rim joist, so I'll have to think of another idea.

On the rim joist it won't matter. It isn't supporting much of a load, it's there to keep the floor joists vertical. Mine go through the rim joist with no issues. The rim joist is completely supported, as are the ends of the floor joists by the wall below. Holes matter in the span of a floor/ceiling joist.

 

[Snoonyb]

Many of the appliance mfgs. will offer a "recommended" performance chart/data.

Enlarging the rim-joist penetration shouldn't be a concern.

In 45yrs I've never in stalled a vent for an over-the-range appliance, of less than 7", and at times as much as 12", W &W/O external motors, and while the CFM of the vent associated with a microwave, is in the 300 range, and in particular configurations could be reduced too 6", I budget for the potential of an upgrade.

 

[skrmisz]

Thank you everyone for your responses, very helpful! I'm glad I found this forum, excellent place you have here.

 

[Sparky617]

Welcome, glad you found us. Post back, it is a pretty friendly place.

 

[Ron Van]

In 45yrs I've never in stalled a vent for an over-the-range appliance, of less than 7", and at times as much as 12",

I installed a Micro/Hood vent combo recently and after researching several manufactures and models, I found they are mostly similar when it comes to vent size and length which is 140' max length of 6" vent pipe. Each elbow, transition and roof vent adds to the length equation. For example, add 10' for each 90 degree elbow, 5' for a 45 degree elbow, 40' for a wall cap, etc. The OPs vent pipe run looks pretty short, so I don't think there is a problem with a 6" vent pipe, a rectangular to round transition, 3 elbows, and a wall cap. He'd end up with 90' of vent run equivalent or so? Which is less than the 140' max.

 

[Snoonyb]

While a "general" synopsis may be true, the pictured vent appliance, is not a MICRO/HOOD, and additionally, the appliance being vented, has not been supplied, and I've found that venting the appliance, results in fewer potential repercussions.