Hood exhaust question: through garage to outside wall? (floor, washer, window)

[C_Lan]

Hello all,

I have been searching extensively and did not see an answer to my question below. However, I may be Google-Blind by now and may have missed the obvious, so if this has already been addressed kindly point me to the thread

I am trying to decide on what type of exhausting I will do to finally get my range hood exhausted to the outside. My range sits against our garage wall and I have a room above this wall. Up venting is not an option. I may be overlooking a simple solution but this nis what I am dealing with:

Option 1: straight through wall into garage, carry ducting up and near ceiling ~15ft from ground (with proper strapping), 3 90degree turns, run of ~15 feet, and out exterior wall. The point where I punch through the wall is approx. 8ft off the ground from the garage floor.

Option 2: Straight through wall into garage, 90degree drop down wall ~ 7 feet, 90degree turn through wall into crawl space, straight run a few feet, 90 degree turn and through either brick or siding to outside.

Option 3: 90 degree turn and stay rect in wall, drop through floor into crawl space, 90degree turn--convert to 6" round, 90degree turn and ~7 feet through outside wall. Similar to opt 2 but I stay within the wall in back of the range. This is of course an insulated wall. Vent opening from hood is 3 1/4 x 10".

Calculating equivalent duct run footage: http://www.zephyronline.com/docs/bra...eze_manual.pdf

Rect to 6" circle: 1 (opt 1)
Rect to 6" circle w/90degree bend:20 (opt 2,3)
90degree bends 3@15: 45 (opt 1)
90 degree bend 2@15: 30 (opt 2,3)
End cap: 30
Straight tube: opt 1 - 25, opt 2,3 - 15

All ducting will be smooth on the inside. No ribbed flex tube.
Opt 1: 101
Opt 2, 3: 105

Opt 1 has vertical rise
Opt 2,3 has vertical fall

Using duct recommendations from Zephyr I will be at/above the suggested 100ft equivalent for each option.

Opt 1 is the most appealing to me due to most of the work being duct work. 2,3 have more cutting/wall work. The million dollar question is...can you run exposed duct work (properly sealed metal work, properly sealed wall work (fire retardand materlials including caulk if it exists) through a garage if that duct work is above the height that you could 'bump' into?
-I have searched the Cary codes and can not find explicit info, only things along the lines of exhausting cannot be done into crawl spaces, garages, or attics.
-I have a call into an HVAC guy to 1) check the code, 2) get quotes for a pro to do the work. My issues is that starting tuesday the sales tax goes up 1% and I' like to buy the vent before the price increase. I have to have this completed before my new stove and tile work is installed on 9/12.
-If the ductwork has to be sealed then I will be forced into option 2 since I would only have to enclose ~7 feet of duct.

Many thanks for any constructive input.

Chris
I live in Cary, NC area code 27519. I originally posted this in the local forum but it got moved to here.

[C_Lan]

It seems as if I've used up my edits!

Should add that the fan I choose will either be 350 or 400cfm. Room size warrants 300 cfm.

[harry chickpea]

Step back to the basics. We vent to get rid of odors, grease, moisture, and heat. I would be uncomfortable running that much venting pipe for an over-the-stove vent because of fear that moisture and grease would condense and create a mess or fire hazard. You can get rid of odors and grease with a good ventless setup if you are willing to clean the grease filter in a washer once in a while and replace the carbon filter as needed. You can get rid of heat and moisture by installing a power vent somewhere else that makes more sense - maybe above a sink with an outside window or above a set of cabinets.

[C_Lan]

Harry,

Our best option with our house design is the hood vent. I cannot get around that and am willing to increase the CFM if needed and use 8" diameter tubing instead of 6". I've been searching more and it looks like if I do option 2 I can reduce my duct equivalent by using good rounded 45s instead of a 90.

Regards,
Chris

[harry chickpea]

If you move the airflow down, you likely will want some way to catch the drips and be able to do a cleanout. If you work that in, you may be ok, although I'd personally not go that route.

[C_Lan]

Originally Posted by harry chickpea

If you move the airflow down, you likely will want some way to catch the drips and be able to do a cleanout. If you work that in, you may be ok, although I'd personally not go that route.

I'm curious about the drip 'pan' too. I know a terminated stub would create resistance to the airflow but the powerful down draft systems must account for this somehow. I'll be checking with a co-worker tomorrow that has the downdraft system and I'll see what type of set up he has.

[Cosmic]

If I had to run vent lines, I would not be going down in direction and going any length horizontal after that. Would also be afraid of creating some type of grease trap. Would not want it enclosed either, if that puppy gets a fire, would want to know it and be able to get too it.

Hot air wants to go up, never fight Momma Nature. Who knows what the codes might say about it. I figure they require metal ductwork.

Common sense to me sezs always run any vent up or horizontal, never down with minimum bends and turns.

[lumbollo]

Originally Posted by C_Lan

.
-I have searched the Cary codes and can not find explicit info, only things along the lines of exhausting cannot be done into crawl spaces, garages, or attics. .....
Chris
I live in Cary, NC area code 27519. I originally posted this in the local forum but it got moved to here.

I do certainly think it is worth venting a stove to the outside. The recirculating ones are pretty useless for certain types of cooking. In NC, I am pretty sure the municipalities all use the state building code. You might already know this and have looked but here is their website just in case you haven't. You would want to look at the mechanical code.

Welcome to NC Office of State Fire Marshal

On your specific question about running exposed ductwork through garages, there are probably a million+ homes in NC with gas hotwater heaters installed in them. All of them have exposed ductwork for the gas exhaust running to the outside so I am thinking you will be fine, but you could call the building dept to ask them or an opinion. Good luck with your project.