Baffles and other filters collect a portion of the grease, a higher percentage of the larger particles and a lower percentage of the smaller particles. What sticks to the roof or wall will depend on temperature differences, I would expect.

A plus for the roof option is that generally the roof gets washed and UV irradiated for free. A negative is that in some climates and with low pitch angles the roof also gets buried in snow, and would require either a raised roof cap or an upblast type blower housing. Otherwise, it may be necessary to run the exhaust fan during the storm.

kas

Thanks for the replies. In my scenario, I would be fine with either the wall or roof cap--both would be through the garage attic. The wall cap would be in a gable wall that is on the side of the garage that doesn't have much visibility. So it comes down to function...what would be best in terms of performance and least noise?

1. A duct run exiting the hood and making a straight horizontal run for approximately 6 feet, then a 90 and approximately 3 feet to the roof cap.

or

2. A duct run exiting the hood and making a straight horizontal run for approximately 24 feet to a wall cap.

If scenario 2 is the best choice, where along the 24 foot run should the inline blower be placed?

Regarding the inline blower, any issues using a Fantech blower with range hood controls? Will a separate control for the blower likely be needed?

Thanks a lot for the help.

I would go for the roof, the rain and sun will help keep things clean, plus shorter run. We get driving rain and only have a 4-12 pitch so instead of a vent that sits on the roof I ran the pipe so it sticks out about 2-1/2' with a flashing and storm collar then I used a cap like you would use on a gas fireplace. Keeps it above the snow in the winter too.

Is there that much junk that comes out of the cap?

As far as the noise, I wonder if it would be best to extend the run a little before going out the roof...to keep the blower a little further away?

Not really, compared to a restarunt, but the shorter run will push it out into the air better. As far as the blower mine is in the hood. Go with the recommendations of the blower manufacturer as far as location. Larger pipe diameter will be quieter.

That 90-degree bend adds several effective feet to the total length (I keep thinking 15'). That may make the total effective lengths about the same.

Actually it's 5' per 90 deg. bend

I would suggest that an in-line fan be placed as far away from the hood as feasible while keeping it accessible for repair. Farther away also allows retrofitting a silencer if desired.

Fan controls built into a hood may or may not work with a particular Fantech fan. This is something Fantech may be better able to comment on for a specific hood. I believe, having inspected its design, that the control in my Wolf hood (standard Triac motor control) could work with a Fantech fan (up to 1500 cfm, at least) as well as it does for the Broan (sold by Wolf) fan that was specified to work with the hood.

kas

If I do need a separate control, are there others besides those made by fantech that will work? So I assume as well that if the hood controls won't work, then there is no way to utilize the heat sentry function?

You will not be able to vent through the garage without enclosing that vent in a drywall soffit. No direct penetrations from the house to the garage are allowed by fire code.

What is above the range area? Why can you not go straight up? A 12" chase can be created to house the duct. As long as it's not in the direct middle of the wall, it can actually add some architectural interest.

I thought about going straight up with it, but I don't have a lot of room due to the angle of the ceiling. Plus, I am going to be using a canopy style hood, so the chase would have to be rather large to be in proportion with the hood, and I'm not sure how that would look. I did think about placing cabinets on top and then a chase above that, but again I am probably too close to the rafters in the attic due to the slope of the ceiling. Consequently, out the wall and into the garage attic seems to be the simplest way to go. Plus, that gets the inline fan away from the house and makes everything more accessible.

I don't mind enclosing the vent in drywall to bring it up to code. While the vent needs to be in a soffit, what about the inline blower? It seems like the blower should be left out in the open, with the remainder of the duct enclosed?

That said, I can see what you are saying about direct penetrations from the garage into the house are not permitted due to fire concerns. However, would a solid duct running from the kitchen into the garage attic and out the roof fall within that logic? There are no breaks in such a duct run, since the only openings are at the hood itself and wall/roof cap. So as long as the penetration where the duct goes from kitchen to garage is sealed with fire caulking around the duct, how is there an issue? Again, I don't mind enclosing the duct run in a chase if need be, but it seems like overkill....

thoughts?