Kitchen Island Downdraft Exhaust - can I build one that really works?

MotoSook · 01-10-2010, 05:06 PM

The wife and I are going through design and planning for a kitchen remodel. Our current stove/range has an inside vent hood that is worthless. I want one that will actually suck and blow to the outside....and over an island.

I don't have a convenient place to vent an overhead exhaust. I may still go this route but I'd have to do some creative ducting and routing. I don't want to have the hood hanging over the island and exposed duct work.

I'm not thrilled with available downdraft ranges or cooktops. So I'm thinking of building a downdraft system myself. I'd build a slim box that will rise up from the center of the island when needed. The box would have vents facing the cooktop with grease filters. The box would be plumbed to a blower that's either under the counter or in the basement. From the blower I would duct the exhaust to the outside at the floor joist level.

I have to find a blower that will work for this. I haven't gotten tothat point yet, but wanted some input for you guys, particularly those that have a downdraft system.

How is your system setup?

How many actually exhaust to the outside? Or is it just dumping the exhaust below the counter?

Is a downdraft really as effective as an overhead hood?

Chuck Grieb · Chuck Grieb's Garage

We have a downdraft from Viking. It definitely works, is very strong, and vents to the outside. Don't know if this is the same model but it sure looks like the one we have.

Professional Series VersaVent Rear Downdraft from Viking , Model: VIPR

BeyGon · 01-10-2010, 05:33 PM

Our stove top is Jenn-Air and every time the stove is on the fan is on, I think it works great, you can see everything being sucked down, it is plumbed to the outsied.

MotoSook · 01-10-2010, 05:47 PM

Chuck,

That Viking is about what I'm going for. We're looking at a 48" stove/range/grill. Do you wish you have more than 600 CFM sometimes?

MotoSook · 01-10-2010, 05:49 PM

Quote:

Originally Posted by BeyGon

Our stove top is Jenn-Air and every time the stove is on the fan is on, I think it works great, you can see everything being sucked down, it is plumbed to the outsied.

What's the plumbing look like? I'm probably going to install it myself. I am pretty sure I can make it work in our arrangement, but it doesn't hurt to increase one's confidence.

I figure if I build on myself, I can put the blower in the basement directly under the island.

BeyGon · 01-10-2010, 05:59 PM

I looks to me, from the outside, not going under to look, it looks like drier galvanized 4 inch tube, I just know where it exits outside the house, just like the drier exhaust. All I did was buy a new one to replace the one that was 18 years old and replace it. My kind of job.

Tim Polzin · 06:16 PM

Just built one for our new house. Don't go less than 250 cu/ft/min. 5 inch line at least. At 600 CFM and probably less, you need some careful consideration of backdrafting from water heater/furnace/fireplace.

Fantech: Inline Duct Fans

Tim

MotoSook · 01-10-2010, 07:18 PM

Yes... An inlined fan @ 500-600 cfm hung in the basement between the floor joists. Perfect.

I want a cooktop with a grill on it so I want to be able to pull as much heat and smoke outside as possible. I want to make I dangerous to get too close to the vents!

jyl · jyl's Garage

I've been researching this.

For a pro-style residential range, that is used for grilling, woking, really high-heat searing, and other cooking methods that generate a lot of grease and smoke, the usual recommendation is more like 1000 CFM with an overhead hood. With a pop up downdraft, that same 1000 CFM is less effective since hot air wants to rise, not fall, and often you are cooking on the front burners which are farthest from the vent. I know I've cooked on cooktops with pop-up venting and the vent could never keep up once the oil smoky cooking started. For milder cooking it was fine.

Here's a wacky thought. Suppose you have a fixed vent that starts from the back of the range, rises, then turns and comes forward to cover the front burners. So, it's got a hood like an overhead vent, but the airflow turns 180 deg and goes down into the cabinetry. Some nicely polished stainless steel - even engine-turned, maybe - and you can call it a "design element". Think of a mammoth racing header.

MotoSook · 08:47 PM

I've been thinking on the same line John. I was thinking of making the popup in sections as oppose to one piece so that I would draw from a smaller area when cooking. The closed sections would essentially block the intake so more vacuum is created at the open section, when not using all burners and grill. Then I thought of a removeable extension that would draw from above (say the grill section since it would create the most smoke and grease).

Your post is making me think of something more complex but better - think periscope that rotates over to the grill when up.

I'm thinking of welding it up with steel them getting it powdercoated in an accent color to compliment the granite ans stainless. The wife likes powdercoated steel stuff.

jyl · jyl's Garage

I think that could look utterly cool, as well as being totally unique.

Or - let's be weird - an articulated arm framework, kind of exoskeleton style, with a 8" diam flexible vent hose inside, blazing halogen lights at the "mouth", kind of like range vent hood meets bionic Dune sandworm.

Well, seriously, the periscope could also incorporate work lighting.

jyl · jyl's Garage

Oh, BTW, one time when I cooked on a cooktop w/ a motorized downdraft vent, I almost dumped a whole pot of boiling water when the rising vent piece caught the pot's handle. I guess if it were your kitchen you'd be wise to that, but I was pretty irked.

MotoSook · 09:16 PM

I just had another thought that isn't as cool but easier to build. Use 4" pipe as risers. The pipes would simply rise and lower, but a rectangular filter housing would cantilever over the cooktop. The fumes would get sucked into the filter housing and down the 4" riser which are connected under the counter then routed to the blower under the floor. The filter housing would rotate forward, pivoting at the bottom of the housing so that it is as much "over" the cooktop as possible.

I can put lights on the front and top of the filter housing, and I can make it as high/tall ( for more forward coverage) as I have room for it to retract. I can maximize the riser length so that the filterhousing sits high above the cooktop.

So I'll have a retractable hood!

MotoSook · 01-10-2010, 09:11 PM

The cantilever hood and pipe riser should help prevent this.

Quote:

Oh, BTW, one time when I cooked on a cooktop w/ a motorized downdraft vent, I almost dumped a whole pot of boiling water when the rising vent piece caught the pot's handle. I guess if it were your kitchen you'd be wise to that, but I was pretty irked.

look 171 · 11:13 PM

Quote:

Originally Posted by Soukus

The wife and I are going through design and planning for a
Is a downdraft really as effective as an overhead hood?

No.

With a grill, you will need something stronger them 600cfm.

Viking or any of the upper end co. make a roof top remote vent for hoods. You might be able to mount it on the outside of the house and duct it to the stove. this way, you do not have to monkey w/special fabrication and having a motor under the stove or the house because it is quieter and you can service it easily if the motor goes bad. don't quote me on this, but most need a 9 or 10" duct. I advice all my clients that if they can swing it in their design, go with a big over head hood. down draft (the ones with good sucking power) suck away too much heat for cooking. My 2 cent. good luck

Jeff

look 171 · 11:12 PM

I have just read the last few post here. Depending on the range type, you might not have the room to do all this because it has to recess under the stove somehow and that needs room. Your gas line might be in the way, but that can easily be fix or re-routed. This is crazy but doable. I have always been called in for these hair pulling meeting with designers and such. Fawking crazy people that have too much money and brain cells. Not directed to any one of you guys but the sensitive decorators that want something that can not be done sometime. They don't know what no is. I would think about using a scoop that comes up from the back of the stove to capture the steam or oil. Just think of a rounded BBQ hood or cover that swings up from the back. The problem is that you can not use flexable vent hose. At least, not legal around here. It traps grease and can cause fire. Having enough room in the back and under the stove is your friend. No need to have crazy lights on the unit itself (less wiring and do not have to find ways to hide them) since there is no overhead vent hood to cause any dark area over the cook top. Use a (maybe 2) low voltage can lights with spot bulb(s) directly over the stove sould be more then enough. If you live in CA, then you have to deal Cal title 24. Flor. lights in the kitchen (but there are ways around that). What's it like up in OR John? Freaking Tree huggers.

Depending on the distance of the ducts, I would use 2 seperate remote fans like I mention on the post above (or inline) that run seperate ducts that will connect up to a single duct near the source . Wired them to seperate variable speed switchs and blow them outside. I really like the remote roof mount units. They are try and true products. Don't forget the in line mufflers to reduce wind noice. They work really really well. I always suggest the installation of one on all my kitchens. I think Fantec makes them.

1990C4S · 01-11-2010, 04:35 AM

I had one of those on my 30" stove. It was adequate, and very quiet. A nice solution, but inferior to a large overhead exhaust fan.

MotoSook · 01-11-2010, 06:16 AM

I don't have the option of venting to the roof my master bedroom is directly above the proposed island. If have a traditional overhead, I would have to run duct between the floor joist under the master br and vent on the side of the house. I'd also have to expose or box the duct else it'd be too small.

My utility room is right under the proposed island so it makes it easier and cleaner to do a downdraft and put the blower in the basement.

So an overhead/hood and roof vent is out of the question.

I'm waiting on a flight at the moment, else I'd sketch up my latest design. I don't think I'd give up much to a hood design and with the blows in the basement I can uprate the flow if I have to.

jyl · jyl's Garage

Quote:

Originally Posted by look 171

If you live in CA, then you have to deal Cal title 24. Flor. lights in the kitchen (but there are ways around that). What's it like up in OR John?

I don't think we have such a requirement here.

I have all CFL in the kitchen's overhead fixtures but can't see using CFL or tubes in the hood, too bulky and not directional enough. I figure in a couple years LED will be reasonably priced anyway.

look 171 · 01-11-2010, 06:58 AM

Quote:

Originally Posted by Soukus

I don't have the option of venting to the roof my master bedroom is directly above the proposed island. If have a traditional overhead, I would have to run duct between the floor joist under the master br and vent on the side of the house. I'd also have to expose or box the duct else it'd be too small.

My utility room is right under the proposed island so it makes it easier and cleaner to do a downdraft and put the blower in the basement.

So an overhead/hood and roof vent is out of the question.

I'm waiting on a flight at the moment, else I'd sketch up my latest design. I don't think I'd give up much to a hood design and with the blows in the basement I can uprate the flow if I have to.

You should be able to run the ducts above between the joist. have square ducts made and hope there's isn't anything in the way. They should fit right above the dry wall or ceiling.