Custom hoods with custom chimney pieces can be provided by some manufacturers. Or, more economically, a stock hood and custom chimney piece can be provided. (Modern-Aire is just one source of many that comes to mind in my present rush.) Generally you would want to obtain both parts from the same source to keep the stainless steel the same.

To keep noise down, aim for a roof-top blower assembly and in-line silencer (see Fantech).

Hood dimensions, flow rates, etc. can be discussed, but have been addressed in general many times on this forum. Some (heh) reading will be needed.

kas

Thanks - Yeah, I've read all the threads (several times!). But every time I think I've figured it out, I go look for what I think is a good pick only to find it doesn't come in 54" or doesn't seem to have a chimney extension option.

From all the reading I've done here and elsewhere, I think I need the hood to extend at least 24" (maybe more) from the wall. I need at least 1200 CFM. I don't want ventless. I want largish ducting (maybe 10" or more?).

I was considering a roof-top blower, but then I read it might not actually be quieter unless it's fairly far away and since I have a flat roof, it wouldn't be. Will definitely look more into an in-line silencer.

I'm not sure if I need to do anything about replacement air, but it looks like some hoods have an option for a component that comes with them that takes care of that. (I live in the Pacific Northwest, so I'm not sure how climate factors in to that.)

I don't think my needs are necessarily that unique, but it's just been weirdly difficult to find any brands/models that seem like they'll work. Initially, I was hoping to be somewhat budget conscious, but I think at this point, I'm willing to get whatever fits my criteria, regardless of cost.

The plumber sub that my original GC brought in is absolutely the worst at, well, talking. He can show up and install stuff (correctly, I guess, but without any care whatsoever) but he's not someone you can ask about what component would best fit your space. In any case, I don't know if a plumber is even the right person to ask, but he's who installed the stove, so he's the closest I've got.

When I go into an appliance store, I haven't gotten much good advice either. It's frustrating, but I tend to get a pat on the head and "let me show you some awesome washing machines, little lady." (I swear this is what has actually happened even when I have specifically said, "I do not care about washing machines. I send my laundry out to a service.") So even if I could bring myself to summon enough patience to get them to help me what I actually need, I sort of don't want to give them my money at that point.

Both Prizer and Modernaire have stock hoods that will meet your needs. And both are well liked on this forum. I have a 42" Prizer hood over my 36" BS range and I really like it. I have an open floor plan and with the hood on low or medium conversation can occur, and the TV can be heard. For hood examples, check out the Prizer Laramie wall mounted, and the Modernaire PS-20. Both come in 54", both vent to the top, come in 1200 cfm and have a chimney that will reach to your ceiling height. Both brands have other options that will meet these specs too. Also, if you find a hood you like but not the chimney extension you like, you can get a custom one done by a metal fabrication shop in your area, and the cost shouldn't be ridiculous. I had a duct cover made for my hood because the hood I bought had an optional duct cover that was larger than I wanted height wise. Unless you're getting a fancy metal (I have brushed SS) the match will be easy if the fabricator is good. Most brushed SS matches, according to both Prizer (who I called to ask about their finish) and my fabricator. The key is to make sure the SS grain is horizontal as hoods are done with the SS grain horizontal.

I believe that Modernaire only sells through select KD's and architects (at least that's the way it works in my area). So if you're not using one of their KD's (or any KD at all), then you may need to go to someone on their list and pay the associated markup.

vanessafox, you're not alone. I've got a similar situation (open floorplan, one story, large BTUs), been reading all the articles, and am muddling through the answers. The appliance people just want to push their product. KD wasn't an authority. Going to talk to the HVAC guy. I have a BBQ grill outside so not sure about venting directly out rather than up. Will also check the inline blower (had also read Fantech was best for inlines and Abbaka for remote blowers). Frustrating that some people can get a good price on Modernaire while those who have dealers nearby are stuck with full pricing. Will be interested in other suggestions from more knowledgeable folks!

OK, I have a bit of time, let me summarize my opinion.

You want to capture and contain the rising and expanding effluent plume. Generally, one rule of thumb is to extend the hood three inches beyond the cooktop on the sides, and make it deep enough (front to back) that frontal burner/hob effluent is also captured. More generally, I would go with an aperture that exceeds the locus of pan bases by a value equal to {the gap between the cooktop and the hood aperture} times {the tangent of 10 degrees}. This corrects for greater gaps when called for by the cook's head clearance. (Eight degrees may be enough in a pinch.) The back wall suffices to constrain the effluent on that side of the hood.

An actual flow rate of 90 cfm per square foot of aperture area should be sufficient, and if you account for all the pressure losses in the path from cooktop through the baffles, through the silencer, through the ducts to the outside, and then back via the make-up air path, you may find that that loss on the fan curve puts your actual flow at about 2/3 of the zero static pressure flow that the blower is typically rated at. Thus, multiplying the aperture area (sq.ft.) by 135 cfm/sq.ft. should suffice for picking a blower.

Due to Houzz truncating posts, more in the next message.

kas

Continuing, the duct diameter should be such that the air flow velocity be in the range of 1000 ft/min to 2000 ft/min at full power (that you would use for serious grease vapor generation). So take your actual estimated cfm with all the pressure losses (ideally at least 90 cfm/sq.ft. of aperture times the aperture area, and divide by the area of the duct in square ft. to find ft/min.

The choice of where in the 1000 to 2000 range to aim for depends on whether the duct passes through cold areas where grease could condense. (Baffles and mesh filters only collect part of the grease particle spectrum.) Use the higher value when the duct will be expected to be cold over any significant distance (NH); the lower value when the duct may be expected to be warm (AZ). Of course, calculating that the duct diameter should be some value like 8.7 inches only means that one should go to the next standard size, 10 inches in this case in the lower velocity direction, or 8 inches in the higher velocity direction.

My maximum Wolf Pro Island Hood uses a silencer and roof cap blower rated at 1500 cfm. I assume that the actual maximum will be 900 cfm when my MUA system is fully functional.

kas

The roof top blower noise (particularly blade tip aerodynamic turbulence) can be pretty well reduced by the in-line silencer. The silencer does not require that the duct be long for it to work, but it does require that there be room for what is a fairly hefty assembly. My hood system at full power makes less noise in the kitchen than the wok being stirred. Conversation is easy at full power. In addition to the silencer I also wrapped the 10-inch ducting with automotive dampening material to remove transmission of vibration down to the hood from the blower. Duct length is (guess) roughly 15 ft.

As I have historically mentioned several times, a side view sketch of the counter, cooktop, hood, and stick-figure cook with sight lines to pots at the back and a waist bending arc for head clearance can help decide what height to use as a function of hood front-to-back distance.

If affordability allows, the hood and its support equipment can be tailored to best fit the cook's needs. If cost is no object, then there is always:
http://www.handcraftedmetal.com/

kas