Thread: Converting downdraft to range hood,but question on effectiveness

Bought this house but wife just font like the downdraft , am going sleepless how to convert this downdraft to range hood. Pic attached

Need your review on these choices, my handy man says he doesn't guarantee the effectiveness in brighter side

1. The wall thickness 3.5" , how about cut the wall and drop two pipes from range hood and connect them to downdraft

2. Handy man thinks the range hoods only exhaust upwards but not downwards , is this true ?

3. After all is it going to be effective

Originally Posted by Kasi Reddy

Bought this house but wife just font like the downdraft , am going sleepless how to convert this downdraft to range hood. Pic attached

Need your review on these choices, my handy man says he doesn't guarantee the effectiveness in brighter side

Does the range back up to an exterior wall or to an interior wall with a room on the back of it (and what room is it)?

1. The wall thickness 3.5" , how about cut the wall and drop two pipes from range hood and connect them to downdraft

Don't do it.

2. Handy man thinks the range hoods only exhaust upwards but not downwards , is this true ?

You need to look at the installation instructions for the range you are going to buy or have already bought - the installation instructions will tell you most of what you need to know on how to run the exhaust duct.

I doubt that they will say it is allowed to run down, probably straight out the back or out the back and up through the roof. The installation instructions will also tell you how many elbows, size of duct, and maximum length of the duct, including length to add in for elbows (probably 5 feet for each 90 degree elbow).

The rest of the information will come from the code, and the code will say to install in accordance with the manufacturer's installation instructions. The only way the code will allow downdraft is if it is a down draft (installation instructions again).

Downdraft duct going underground have specific requirements that above ground ducts do not have.

3. After all is it going to be effective

Probably not.

My suggestion if your wife does not like the downdraft is to cap the downdraft duct off inside and outside (required by the code) and to install a high quality ductless (recirculating) range hood.

Originally Posted by Kasi Reddy

Bought this house but wife just font like the downdraft , am going sleepless how to convert this downdraft to range hood. Pic attached

Need your review on these choices, my handy man says he doesn't guarantee the effectiveness in brighter side

1. The wall thickness 3.5" , how about cut the wall and drop two pipes from range hood and connect them to downdraft

2. Handy man thinks the range hoods only exhaust upwards but not downwards , is this true ?

3. After all is it going to be effective

Welcome Kasi,

Not sure what you are asking or trying to do.

If a vent pipe is installed above the Range but no vent fan then just install the Exhaust fan
to the vent tube using the Vent hoods Manufacturing installation instructions. Happy cooking from then on.

Thanks much!... Its not a ext wall back of the stove but hall way

q2.. Just curious if any deterrent factor for dropping the pipes through the wall and so the downdraft fan pulls the air?

Originally Posted by Jerry Peck

Does the range back up to an exterior wall or to an interior wall with a room on the back of it (and what room is it)?



Don't do it.



You need to look at the installation instructions for the range you are going to buy or have already bought - the installation instructions will tell you most of what you need to know on how to run the exhaust duct.

I doubt that they will say it is allowed to run down, probably straight out the back or out the back and up through the roof. The installation instructions will also tell you how many elbows, size of duct, and maximum length of the duct, including length to add in for elbows (probably 5 feet for each 90 degree elbow).

The rest of the information will come from the code, and the code will say to install in accordance with the manufacturer's installation instructions. The only way the code will allow downdraft is if it is a down draft (installation instructions again).

Downdraft duct going underground have specific requirements that above ground ducts do not have.



Probably not.

My suggestion if your wife does not like the downdraft is to cap the downdraft duct off inside and outside (required by the code) and to install a high quality ductless (recirculating) range hood.

First, the installation would need to be in accordance with the manufacturer's installation instructions.

Second, an above the range hood is not designed for downdraft exhausting of the air.

Lastly, the downdraft ducts would need to comply with the attached NC code section.

I did exactly what you are talking about at my house. Not saying it's to manufacturer's specifications or to code, but it works ok. It would certainly work better if it was all going up and out, but it's not a whole lot different than a down draft fan. I went straight back from the hood into the wall, down about 5 feet in a 3.5" wall, and then out the crawl space via an 8" round vent. I was not on a slab, but you can probably tie into the down draft under the cabinet if you are. Each turn will decrease the efficiency a little bit. I wasn't sure if it was going to work or not, but it definitely does work. A stronger fan is a big help. If I did it again, I would probably get a little more CFM on my fan.

Ideally you should go up because warm air wants to rise. I would forget the downdraft and install a pipe in the ceiling, between the joists if there's a floor above.
Use rigid metal pipes. Flex ducts trap grease. Rectangular ducts work well.

You can go up through the cabinet and then conceal a horizontal pipe behind a soffit cover. Across the tops of the cabinets to an outside wall.

The smaller the pipe diameter, the noisier the fan. I installed a nice stainless hood with a stainless housing hanging from the ceiling, but ..... all that metal amplifies the fan noise. If you can install an inline fan on the duct up in the attic, that is the best for a quiet range hood. A noisy range hood doesn't get used very much. It should have 4 speeds.

Thanks both Jim and John!

Jim - so this group will be able advise further more, did you hv to install 2 fans one on the top and one under the cabinet , lets say if both fans are same kind and also operate with only single switch ...does it provide consistency on exhaust?

Originally Posted by John Kogel

Ideally you should go up because warm air wants to rise. I would forget the downdraft and install a pipe in the ceiling, between the joists if there's a floor above.
Use rigid metal pipes. Flex ducts trap grease. Rectangular ducts work well.

You can go up through the cabinet and then conceal a horizontal pipe behind a soffit cover. Across the tops of the cabinets to an outside wall.

The smaller the pipe diameter, the noisier the fan. I installed a nice stainless hood with a stainless housing hanging from the ceiling, but ..... all that metal amplifies the fan noise. If you can install an inline fan on the duct up in the attic, that is the best for a quiet range hood. A noisy range hood doesn't get used very much. It should have 4 speeds.

I though that I might have to add a booster fan in the crawl space, but it works pretty well without it, so I didn't bother. Our run is pretty short, which helps. If the down draft fan is still present, and you can put that to use, it should work pretty well. I wanted the open soffit above the cabinets, so I was willing to trade off a little of the effectiveness for it. It hasn't been a problem for us so far. My biggest problem is that my furnace vent blows right onto the range cook top, so the smoke from my pancakes gets pushed out to the side of the hood. Haven't corrected that yet, but that has nothing to do with the down draft setup.

Originally Posted by Jim Robinson

I did exactly what you are talking about at my house. Not saying it's to manufacturer's specifications or to code, but it works ok. It would certainly work better if it was all going up and out, but it's not a whole lot different than a down draft fan. I went straight back from the hood into the wall, down about 5 feet in a 3.5" wall, and then out the crawl space via an 8" round vent. I was not on a slab, but you can probably tie into the down draft under the cabinet if you are. Each turn will decrease the efficiency a little bit. I wasn't sure if it was going to work or not, but it definitely does work. A stronger fan is a big help. If I did it again, I would probably get a little more CFM on my fan.

Just agreeing with Jim on fan capacity...my experience is that the downdraft fans can be twice the CFM of the range hoods (400-500 CFM vice 150-200), so it would be good to check capacities. the greater distance between the fan and the source of fumes may reduce performance. Modifying a packaged unit - I.e., disconnecting the fan - may have risks. And, of course, changing the volume of air into/out of the home can affect indoor air quality and safety. More codes to check.

A side drafting (auto extending type) would work in that location. They vent downward and are more effective than Jennair type as they extend above the counter top when turned on.

If you are thinking of using an overhead hood with downdraft system then you would certainly need follow size, length and number of fitting restrictions per manufacturer. The fan CFM is reduced if a greater pressure drops occur (long duct runs and fittings). As others have stated here you could add a larger fan and I suggest you consider the following provisions:

1. The fan should be sized for the manufacturers CFM at the pressure drop of your system design.
2. The fan (and wiring methods) should be rated for kitchen hoods (fire, heat, moisture resistant)
3. The ductwork design should include grease traps for collecting condensation and grease at low points and not restrict air flow.
4. The hood should have a clearance of 30" above range surface (or per manufacturers recommendations) Less clearance inhibits access, more clearance reduces effectiveness of hood.

Best bet is too install a "store bought" system and follow their recommendations.

Good luck.

Originally Posted by Ken Amelin

A side drafting (auto extending type) would work in that location. They vent downward and are more effective than Jennair type as they extend above the counter top when turned on.

If you are thinking of using an overhead hood with downdraft system then you would certainly need follow size, length and number of fitting restrictions per manufacturer. The fan CFM is reduced if a greater pressure drops occur (long duct runs and fittings). As others have stated here you could add a larger fan and I suggest you consider the following provisions:

1. The fan should be sized for the manufacturers CFM at the pressure drop of your system design.
2. The fan (and wiring methods) should be rated for kitchen hoods (fire, heat, moisture resistant)
3. The ductwork design should include grease traps for collecting condensation and grease at low points and not restrict air flow.
4. The hood should have a clearance of 30" above range surface (or per manufacturers recommendations) Less clearance inhibits access, more clearance reduces effectiveness of hood.

Best bet is too install a "store bought" system and follow their recommendations.

Good luck.

Correct. And describing how to do something which is wrong to make a wrong installation 'wronger' (too bad that is not a word ) is not something we should be doing here. I can see telling someone how to do something the wrong way 'because it worked for me' and then that inspector entering the house without realizing it was that house and then writing up the installation because it is not right ... ... that would not be a fun day for that inspector in trying to explain why they are writing up what they described doing.