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I am an architect and my client wants downdraft exhaust

Hi I am an...

Hi I am an architect and my client wants downdraft exhaust system for BBQ grille because she does not like to see Hood.

Contractor's Assistant: I'll do all I can to help. How long have you been dealing with this?

My question is that do n't I need a duct work under the floor and then out to the exterior?

Contractor's Assistant: Have you talked to a construction professional about the floor?

There is a crawl space underneath but noway out other than the roof.

Contractor's Assistant: Do you plan on doing the work yourself?

No. I will just design but I need to know if the duct work has to continue to the roof

Contractor's Assistant: Anything else we should know to help you best?

It is a story commercial building and construction has already started

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Answered in 21 minutes by:
1/19/2018
MattR757
MattR757, HVAC Technician
Category: HVAC
Satisfied Customers: 67
Experience: 18+ Years experience in residential and commercial HVAC service and repair
Verified

Downdraft kitchen exhaust is typically ducted to the crawlspace and vented to the outside with an exhaust hood through the foundation wall (similar to a dryer vent hood but usually 6 inches or larger) - The duct does not have to go up to the attic - once ducted down out of the cabinet it can be horizontally vented out of the crawlspace.

Some of the downdraft hoods can be converted to recirculating hoods with a recirculating kit that has an outlet in the toe kick under the cabinet, however, recirculating hoods aren't great for char grillers or indoor flame grills because the smoke and smoky odors get discharged back into the kitchen.

MattR757
MattR757, HVAC Technician
Category: HVAC
Satisfied Customers: 67
Experience: 18+ Years experience in residential and commercial HVAC service and repair
Verified
MattR757 and 87 other HVAC Specialists are ready to help you
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Just for some clarification:

The hood vents down through the cabinet and into the crawlspace or basement... Once the downdraft duct is out of the cabinet and into the crawlspace you can run the exhaust duct to the outside pretty much any way that the construction will allow as long as you don't exceed the manufacturers maximum duct length - For example... If you have a duct chase from the crawl space to the attic you could run the duct back up and vent it through a roof vent or gable vent instead of making a penetration through the foundation wall - This might be preferable if the living space is close to grade, if you're in a location that has to account for snow accumulation depths, or if the exhaust discharge itself would cause issues (like discharging on a sidewalk or driveway, near windows etc)

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Customer reply replied 6 months ago
My situation is more complicated than that.
Being a commercial building the building is built to to the property line and the duct has to go up to the roof.
I can send you the cross sections if you send me your e-mail address.
The owner wants to know approximate cost as well.

Happy to take a look - Being a commercial application there might be some codes / regulations considerations depending on your locality. Our local codes enforcement treats commercial exhaust from indoor grills as grease duct and it has to be seamless joint stainless steel. I could run it by my local contractor group and see how we would handle it & let you know. My email is***@******.***

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Customer reply replied 6 months ago
The project is located in 3900 West Sixth street, Los Angeles. California
Here are some facts on the exhaust vent;
The travel distance of the duct is approx. 72 feet.
The duct has to make 5-6 "BENDS" (turns)
We could clear 10 feet from the property line to the location of the fan on the roof.
What would be the efficiency compared to the Hood system which vent straight up to the roof
which could be 50 feet duct length, 3 turn.
How do I find out the budget?
If you send me the e-mail, I could you send some sketches.Stuart Ahn
I'm not entirely sure that I could accurately estimate cost on the project. You would probably have to contact a local mechanical contractor that does duct work. As far as the equivalent lengths, there should be some info from the manufacturer to define the vent specifications. My email is***@******.*** if you want me to look at the drawings.
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