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Venting Higher then 36" from Counter

Posted by aloha2009 (My Page) on
Sun, Nov 25, 12 at 12:28

Though this isn't recommended, it is within code to go up to 48" above a cooktop.

For those that have a vent 37+" over the cooktop, how well is it working for you? What size vent with what size cooktop do you have? CFMs? Distance from cooktop to vent?

Follow-Up Postings:

RE: Venting Higher then 36" from Counter

The ones I've run into that work well were dramatically oversized in width. The way I was taught is that the loss of efficiency is logarithmic for every inch past 30". Therefore increasing cfm does not do all that much.
I have seen several set at the height you are talking about, twice as wide as the cooking surface and worked wonderfully.
Since things can always come back to bite me I stick within the manufacturers guidelines.

RE: Venting Higher then 36" from Counter

I do not have one of these situations but the Futuro Futuro hood is meant for ceiling or shallow soffit installations.

It is recommended for installation height of about 43" (110cm) which puts it at about 6'7" from the floor in a 15" soffit, and it can be installed up to 59" inches above the cooktop, which puts it at 95" above the floor.

Most pictures of it show it at the higher placement, however the installation guide indicates "some loss of efficiency" at the maximum height.

In order to make up for the distance, the hood has a large size (54") and a huge CFM 2 1880. (Two 940 CFM blowers).

I would be afraid that this would start tugging at one's hair. Clearly this would need make up air as well.

Anyway, it appears that for hoods above 36" the CFM would have to be quite a bit higher than average.

I am curious, according to what code is there a maximum height? Local? I am not aware of this in the IBC.

RE: Venting Higher then 36" from Counter

Look at restaurant ventilation designers to give you something that will provide enough square footage at the height you are talking about. Effluent rises in a cone shape, and the further the vent is from the cooking surface, the larger and deeper it will need to be if it's going to actually work and not just be decorative. I've seen one studio where a cooking show was filmed, and in order to provide the correct ventilation without obstructing the camera view, almost the entire ceiling above the cooking zone was a filtered capture area. The CFM was low compared to most restaurant situations, and could be lower because of the huge capture area, but that very industrial look isn't a look that most people would ever want in a residential situation.

RE: Venting Higher then 36" from Counter

Jakuval, I was looking at going with a 36" vent (at least) for our 30" range.

Interesting that Jakuval and Palimpsest differed regarding CFM. At 1880 cfm, I'd think it would suck the pasta right out of the boiling pot!

IF and that's a big IF we do this, at least 2 windows would be flanking the range providing additional venting if needed (we're debating about having the window above the range being operable - and we haven't even checked code for that specifically.

I was hoping those that have actually have this configuration would respond also since practical living day to days speaks even more volume. Many thought that having a window in front of range would be a grease mess but those that have it say it's not much of a problem and much less then having a sink in front of a window. I know this is less then ideal situation but there's always a bit of give and take when designing it seems.

RE: Venting Higher then 36" from Counter

Put a 42" futuro over a 36" cooktop,(not a pro style) at 30" above the counter. Client doe not find it effective.

RE: Venting Higher then 36" from Counter

I had a 60" range and built a window above it to enjoy the view while cooking. To make the window look right, I needed to raise my hood up to about 38". It was a 1500 cfm. The range had a grill and a griddle and six burners. Grilling created the most smoke by far, and the hood had no trouble keeping up. I was nervous about it at first because everything says to keep it lower, but it worked like a charm. Extra bonus: While you are cooking and the hood is that high up, it feels a lot more open and roomy. Very nice balance.

RE: Venting Higher then 36" from Counter

1. You need more overlap. FWIW I have a 30" rangetop, a 42" vertical gap between rangetop and canopy, and a 54" wide canopy, bumped out 9" from the wall. If you do the trig I'm allowing for a modest 12 to 15 degree angle of expansion of the rising effluent cone. (Kaseki's rule of thumb is 22.5 degrees) I have a blower rated at 1,000 cfm with a very short run to the outside. This setup is just enough, I can attest from repeated observation, to handle the visible effluent rising from a wok on the front burner. I still set off the smoke detector every now and again.

2. Code most places prohibits windows in front of or within a foot or so on either side of the stove. And windows do not necessarily make the task of the hood easier - they can give you cross-breezes and so forth. You do need adequate makeup air flowing in from somewhere (mine comes from just below the rangetop).

RE: Venting Higher then 36" from Counter

We have our hood at 38.5" above a 60" range, pulled out to 27" from the wall and find it works fairly well, if you get the blower going first to create something of an air curtain before you start making smoke and/or steam. We have a roof-mounted 1500 CFM blower with in-line damper. Not noisy until you have it at full power.

It is more comfortable to work under a hood that is set higher like in a restaurant kitchen, but to make the ventilation work well it really seems like you need to create a larger capture area than is standard in residential settings, as in a wider and deeper hood, and you need to use a higher powered blower.

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