Help: Vent hood installation

[elf feet]

Hey guys, I'm installing a vent hood in my kitchen and have a few questions. I've researched online but nothing I've found has really helped.

1) I used a buddy of mine to install ducting for the vent hood. He installed flexible ducting similar to dryer ducting. Every thing I've read says to use non-flexible ducting. Is this a big deal? He knew it was for a vent hood. Do I need to replace this with non-flexible ducting?

2) I am installing it into the bottom of my cabinet. The bottom is made of particle board. If I install wood shims to the bottom of the particle board, is this enough to hold the vent hood or do I need to replace the entire bottom with something more sturdy?

Thanks, guys!

[Split Arrow]

Any help?

[PapaD]

1. Depends on size of blower and volume of air you need to move. If you are installing a large hood (Vent-a-Hood, Wolf, ect.) the installation sheet will probably recommend a 10-12 inch smooth wall ducting. It's been a while since I looked but I believe vent a hood had a chart indicating cubic feet of air moved through various diameter and lengths of ducts. I'm making an assumption that since it's under cabinet, it's not a large/commercial hood, so flex duct might work if it's large diameter (8-12 in). But I wouldn't use the smaller stuff like 4-5 inch. Obviously the rippled sides of the flex duct is going to disrupt air flow to some degree.
2. If it's not all that heavy you could just put another bottom in the cabinet of 1/4 - 3/8 plywood and fasten through both. Put a strip along the edge to tie the plywood to the sides of the cabinet since your weak point may be where the particle board is butted to the sides of the cabinet.

Hope it's of some help, good luck with the project.

[Buckshot4900]

Flex duct will collect grease and eventually be a fire hazard. I would install regular duct.

[Britton]

^^^That is what I was going to say. Call the closest restaurant supply store like Ace Mart and they can most likely point you to someone who can help.

[Atfulldraw]

there are a bunch of vent hoods out there with flex duct on them....

I would prefer to use the ridgid pipe, although they will all collect grease in the seams and bends of any pipe.

More important than the pipe used is where he vented the exhaust.....

[elf feet]

Thanks, y'all.

The duct that was installed is 4" and vents outside about seven-eight feet from the vent.

It's a larger, home vent hood.

After some more research we decided that we needed to email our friend. We're walking a fine line because we don't want to harm the friendship and this isn't the first thing we've found to be wrong. Building code states that it's supposed to be rigid and our buddy said that he should've known better.

He's going to fix the duct work this weekend and help us install the hood.

Thanks for the replies!

[Buckshot4900]

Should also be no smaller than 6". Just saying.

[BowSlayer]

Should also be no smaller than 6". Just saying.

This^^^^ most are 8"

[M.E.B.]

As long as it is METAL flex duct it should be ok. Not the kind used for dyer vents.

[Buckshot4900]

This^^^^ most are 8"

Correctamendo

[Chef]

I don't remember the cfm of my gen-aire hood but we went 8' out of the roof. Make sure you clean the filters monthly. I don't fry in the house and mine get nasty from normal cooking.