Rectangular duct running between joists is OK also.
If the duct will become "inaccessible" under sheetrock, it is best to try for a straight line to the outside so if cleaning is needed at some remote future time, the duct can be accessed by removing the exterior cap.
If I were char broiling into a long duct, or even doing daily wokking, I would want to think about duct access. The baffles of a conventional hood and blowers of a VaH hood both work by centrifugal impingement, and can only capture a portion of the grease particle spectrum. Removal of the rest depends on the air flow, but this is only partially successful. Commercial ducts require access and yearly inspections.
In critical commercial circumstances where better collection is needed, there are special filter packs supplemental to baffles that expand the portion of the spectrum captured.
For the same airflow, a remote blower should be quieter than a local VaH blower group. However, the last quasi A/B test that I know of was performed and reported here by member "clinresga" a few years ago based on his measurements in two houses, and I do not know if VaH have improved the sound levels of their squirrel cage blowers since then.
Your HVAC person needs to estimate pressure losses before you select a hood and blower configuration. This will be particularly critical with VaH because their blowers' fan curves (as far as I know only publicly provided by a few data points) show a greater loss of flow rate with pressure loss than the more conventional designs provided by other hood manufacturers. In either case, the blower configuration has to provide the needed flow rate with all the pressure losses of ducting and make-up air supply, along with the loss across the baffles where applicable.
Check the building code to determine if you need 1200 or 1500 CFM.With a 48" range top, you may not only have to have 1500 CFM, you may also need some kind of air circulation mechanism depending on size of the room, maybe that's the additional mechanism you mention. Whoever sold you the range should advise.
Where is the remote blower to be located? On the roof or the side of the house?
Remote blower on vent hood - much quieter?
Vent Hood Insert & Remote Blower Lead Time?
Will a 1200 CFM blower be just as effective in 63" hood vs a 48" hood?
Remote Range Hood Blowers: hood brand or generic?
Why a Wolf? Have you looked at Vent-a-Hood. We had a 48 inch Wolf ventilation hood in our previous house. It vented directly out the back. It was so loud that we hated using it. In our new house we have a 48inch Vent-a-Hood and it is so much quieter.
We have a Thermador remote blower for our 48" hood. It is on the roof which is one-story at that location. If you are outside it is very loud. Also the box itself is surprisingly large and unattractive. If yours is to the backyard area, it will be pretty annoying to anyone hanging out near it when you use the vent.
Our blower is 1200 cfm, but we have the griddle which doesn't smoke like charring will. You'd probably want the larger blower with makeup air. We're in CA too and grill outdoors year around and wouldn't want an indoor grill again.
I was told that if the remote is farther from the hood, you'd need a bigger blower.
Our Vent-a-Hood has 4 magic lungs which are in the hood itself. It is 1200 cfm but is equivalent to 1800 due to it being centrifugal filtration. We have a 48 inch Platinum Blue star range. We grill outside. After having the Wolf hood and it being so loud I didn't want to have that again.
Yuck! I hate rats. We have a big Viking bbq with cabinets and drawers underneath. We had a rat make a nest in a cabinet by climbing in through the gas hose hole. Thats been plugged up now and no more issues. Rats can't get to the grill area because its covered with a big lid.
We had an indoor grill at a former house. We were excited to use it until we realized what a pain it was to clean and how smokey it got. We were grilling asparagus, not steaks. Ended up not using it much. This time we got the griddle which is a snap to clean, but only use it for quesadillas and grilled sandwiches mostly.
Please review the first dozen pages or so of Greenheck's guide for general principles of kitchen venting. http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdf. Although this document addresses commercial kitchens, the principles addressed apply to residential pseudo-Pro cooking installations.
You will find on page 9 that electric and gas char broilers require more specific air flow (feet per minute air velocity equals CFM per square foot of hood entry aperture) than general cooking does. If your hood is only as large as your cooktop, and say 24 inches of front-to-back entry aperture distance, then the opening is 8 square feet, and it would be appropriate to achieve 8 sq. ft x up-to-185 CFM/sq. ft. This value is nearly 1500 CFM by itself, and doesn't account for the fan curve reduction in flow pulling air past the baffles and other pressure losses.
Note that the commercial units in the table of Greenheck's Figure 4 may be larger than your range's broiler, as will be the hood sizes, and depending on the unstated size relative to the broiler under consideration, may allow operation of a residential gas char broiler at less the 185 ft/min value. But it won't be as low as the 85 value in the Medium column.
Silencers come from Fantech, and for a 10-inch duct are 14-inches in diameter and 3 ft long.. They won't fit in a wall between a hood and an exterior wall blower or wall cap. They need some duct length.
It is a bad idea to dump the cooking effluent into an outside sitting area. You will get grease on everything in spite of conventional hood baffles or VaH magic lung blowers throwing the grease particulates at the hood structures hoping for impingement.
VaH blowers are at best rated for their behavior in the hood, which doesn't for them have separate baffles. However, if significant ducting or MUA pressure losses are present, their claimed 1.5 X equivalent performance erodes faster than conventional blowers defined by their fan curves. Thus each option needs to be separately analyzed.
I think for this relatively extravagant residential kitchen appliance, a more commercial approach to venting will be needed, and the vented air needs to be eliminated at a roof line using a down-slope centrifugal blower such as Wolf or Broan supply, or preferably upwards using a modest sized up-blast blower. This may require use of an outside chase to get out of the patio area.
Generally, a remote blower with an in-line silencer will have the lowest noise at the cook's ear.
I would like to see the size of the air exchange module that can handle 1500 CFM of MUA. Normally, the MUA is supplied either passively with limited heating and filtering, or with its own blower and control system. MUA issues can be researched here in many MUA related threads. I would just note that dealing with the MUA aspect is often more complex than the venting aspect.
Looks like an exterior chase in that location would have to encompass a lot of beams and would certainly reduce the elegance in that area. If the beams are not structural then the chase could be used but the beams made to look like they are going through the chase, but would be truncated at the chase sides.
Perhaps a duct exiting in the triangular space above the window could be passed across the patio. It might be possible to enclose it (horizontal chase).
If a duct went up into the second floor would it be an eyesore in a room, or is there a closet or something above the range it could hide in?
Anyway, if the cooktop has changed from the initial post, we can re-evaluate the required flow rate.
I took a picture of my remote blower just to give you an idea of how big and ugly it is. Its not a big deal for us since its on the front roof of a backward hillside house and not that visible from most locations. But it would sure look ugly (and be noisy) in your seating area.
Forgot to mention our range is centered in front of the window.
The Wolf/Broan 1200 and 1500 blower assemblies aren't as high, I think. Best to look up the dimensions before taking any action.
The Wolf blower is more slanted I think. But for roof install, you need a special bracket (sold separately) that raises it up some, so its higher than just the blower dimensions.
Here's what the Wolf blower looked like at our old house. Ours was on the side of the house. This was back in 2002 so not sure how much they have changed.
Thank you all for sharing your experiences and expertise. The photos are also really helpful and wow those remote units are large!
We are waiting for our HVAC guy to let us know when he might have some free time to come onsite, and we have reached out to a different appliance store to look into Ventahood, Modern Aire and other brands to assess options
The points raised have been very insightful and helpful!
To answer some questions asked....
The kitchen layout really needs to stay as is from the CAD drawing...moving an inch here or there ok but redoing layout is not an option. Since we're still in cabinet planning mode it's ok to modify. But we're about 5 weeks to project start so we have to get those orders in.
Not buying the chargrill version of the Wolf 48" rangetop is an option (i.e. no penalty to us yet to go all burner or griddle) Not sure that will effect the venting issue we have with the covered patio.
Covered patio runs most of back of house. Seating will be right near vent area (in our pix where the window current is). so noise, etc still a concern.
The 8x8" supports for the covered patio go onto the top plate of wall framing of the house between two stories....not messing with that.
The Master Bathroom is directly above the kitchen. The windows for the bathroom are directly above where the oven and stove will be situated (the sinks in both locations access air stack on the roof). Can't do vertical run to second story/roof master bathroom is in the way.
Thank you all again for the input.
And for sharing...really appreciate it. Hopefully we'll get this figured out in the next week or so.
Don't get all the technical details provided but i'll just say, I had a Vent-a-hood and loved it.
As long as we are playing with your (OP's) house, is there [will there be] any way to take the hood exhaust and route it down to a basement and then push/pull it sideways to someplace where it can be exhausted to the outside in order to avoid dumping cooking exhaust onto the patio. This would use a lot of bends and require either a higher power (flow rate) blower beyond the hood or a blower supplementing the blower in the hood (due to the increased pressure losses of this tortuous path.
Or, as a last resort, the blower assembly or cap on the outside wall near the top of the present window could be aimed sideways, or diagonally down to keep the blown air away from patio occupants. The cap shouldn't pick up any rain under the patio roof.
No matter how aimed,, you will have to clean the siding now and then. In my experience, roof contamination from roof mounted down-slope blowers (I have a Wolf made by Broan), is modest enough for sunlight to disassociate any grease on the roof that rain doesn't clean. There is no grease build-up. A shaded wall might not be self-cleaning.
I love my vent-a-hood too and where i live you will need make up air and I run a catering biz with a 36” range , a 48” is even large for a lot of restaurants and if you want to know how noisy the blower is just go to small restaurant and check it out.They are noisy both inside and outside. As for grilling in the house it makes a mess and you will need more CFM than you think. I have never had even a mouse in my outdoor grill and we live in a forest so maybe check out a different grill for outside.
We met with our HVAC guy today and are going to be opening up areas of the ceiling to see what if any obstacles would be in the way to run this horizontally between the floors and out the side of the house where noise and seating are non-issues. We are not sure we can run 10" duct work given the manufactured tresses this place was built with in the laste 80'. He would know...it's why we had to separate the new AC system by floor.
It's possible we may have to run multiple duct lines depending on the size of the system. Vent A Hood has been recommended not only the you all but also the applicance store so we are now trying to come up to speed on the choices they offer.
We are going to decide betweent he 8 burner or 6 burner with char-grill...not backing down from the 48". As for the Weber grill outside...it was the replacement to the built in DCS we removed...which was also overrun by rats etc apparently that chewed the gas line before we bought the place. Never going back to built in outdoor grill/kitchen/island...we'll leave that to others happily!
As for other venting options floated...California houses like ours don't have basements...earthquake country. And fires. And lots of wild life (aka coyote, fox, etc not just the rats, snakes and ants) that find their way to our yard! Rainy season won't start for a few months unless there's drought again.
We'll let you know the outcome of the great ceiling opening effort next week.
For now we're onto researching what we really need from Vent A Hood. And figuring out cabinet functionality.
Thanks for the continued information and feedback
Have a good weekend.
Here's my 1000 cfm Prizer roof blower back in 2013 just after install...
Can you share your experience with us. What did you finally do? We are in same boat with 48" range and lot of aromatic cooking. Thanks.
Hello. Hope this helps you out
We bought the 1200 CFM liner unit from vent a hood. It has two 8 inch vents Which we ran about 20 feet through the trusses to the side of the house keeping away from the covered patio
We did not buy the air exchanger since all we need to do is crack a window or door open and the climate here is pretty mild
We ended up Replacing the originally installed dampers with spring loaded units As stronger gusts of wind caused the flap to bang annoyingly.
If you’re buying the char broiler version of the wolf 48 inch range top suggest you go to In Showroom and try it out
one thing that was a surprise to us is that it has only one setting,high, and we have been struggling with it it burning food. Even low-fat meats seem to burn and we have had fox appliance down several times telling us there’s nothing wrong with the unit
In retrospect we would not buy that unit again Because the temperature is not variable. That is probably the biggest disappointment in our kitchen and the Venta hood was specified for the output of that grill unit
Good luck with your installation!
Oops. Box appliance sorry for the typo
Here are the images to help
jrjunk: Thanks for the update. Would you mind commenting on the sound level at full power. Can two people speaking in "daytime" voice levels converse at the stove?
It doesn’t bother us. But it’s also not on for extended periods at full like that for us. Just usually during the charbroiler use
Thanks for the reply. So it's a remote blower, right? You did not choose Wolf for remote blower?
Ours will be 48" with griddle (NOT charbroiler) but our worry is aromatic cooking which will make whole house smell. Hence wondering what is the best solution?
We found the wolf to be louder and less powerfulwe would’ve needed more CFM‘s where the Venta hood provided a better and more elegant solution for uswe also wanted LED not halogen lights
suggest you take a good look at the specifications with your contractor to make the best choice not just the aesthetics...
We would choose the griddle since there’s no eight burner solution for the range top if we were doing this again given the problems that we have with the charbroiler
You should size the CFM’s to the output of the griddlewe had to size hours to the output of the charbroiler
We spoke with both Wolf and also ia rep from ventahood
It’s worth making the effort upfront more than that can’t really help you with
I'm curious why you didn't use the transition piece so you would only have one vent coming out of your house?
I always wonder how does once decide CFM based on Griddle? We need help deciding CFM based on aroma of cooking, like Chinese for Indian cooking.
Can we go some place and actually hear remote blower so that we understand noise level rather than imagining it.
We have Wolf sales store but they are not of much help. Do I need to call Wolf or Vent a Hood company?
Also in Winter, can't crack open windows all the time? I guess we will need air exchange module? Who helps us decide if we need it or not?
CFM: I use the Greenheck Guide velocity row in the table below as a guide, generally recommending an achieved 90 ft/min across the hood entry aperture. (Note "wok" refers to restaurant grade wok cooking with 100k+ BTUh burners.)
Note that with these flow velocities (which imply volumetric flow rates) all that is captured is contained. So for odor control it is necessary for the hood to be large enough to provide capture of the cooking plumes without any missing the hood edges.
Cracking open a window is insufficient even in summer. Opening windows to approximately the area of the hood entry aperture might be sufficient to keep pressure loss to a value insufficient to seriously degrade hood performance. This is why make-up air systems exist -- to provide low pressure air back to the kitchen. This may work OK passively (no MUA blower) or may require a blower. You will need more than an air exchange unit with the air flows that are typical of serious cooking. You can heat electrically or hydronically without too much trouble. Heat required may be inferred from this graph. Note flow rate is actual, not blower rating.
Noise: Wolf has some distributors that operate demonstration kitchens. I only know of the one in Massachusetts, but I believe there are others; SubZero/Wolf will answer their telephone and try to be helpful.
In any case, noise is a difficult thing to even agree on the measurement of; so, unless two manufacturers agree on the measurement approach, their results may not be comparable. I believe you would be OK with an exterior blower and intermediate silencer. I haven't heard any VaH systems lately to compare.
Will I need Air Make Up system with high CFM exterior blower as I can not open windows in winter? I read one needs it to replace air being sucked out or can feel dizzy with low air pressure? Is that true?
As soon as your blower exceeds a nominal 400CFM, building codes require make-up-air. There are a few select states in the US, where this doesn't hold; California would probably be the most notable exception. But for everyone else, that's the law.
But even if you happen to live in one of the few places where code doesn't require make-up-air, it is a good idea. A vent hood can't vent air, if none comes into the house. If you have a big window opening that always stays open, this might not be an issue. And there definitely are temperate climates where people do that year round. But if you don't, then lack of make-up-air means you have a high chance of sucking air back through the furnace or water-heater exhaust stack. All of that is harmful gas, including possibly carbon monoxide. This is really not a situation you want to be in.
Depending on climate, it also can suck moist air into your walls, which will cause long-term damage.
Why don’t you talk to your HVAC or GC contractor, Or call wolf technical support If you can’t go to the show room
We’re not professionals So it’s beyond our scope to help you with CFM sizing
@jrjunk, that's really uncalled for. While it ultimately makes sense to talk to professionals, this forum has repeatedly demonstrated that not every contractor is equally proficient in their field. It's a good idea for homeowners to do their homework, so that they can ask contractors good questions.
And there actually are a lot of people in this forum who have done the research and understand about how to properly size vent hoods. This still doesn't substitute for a professional performing actual measurements on site. But its a good baseline.
And if the back-of-the-envelope calculation tells you that you should have 900CFM and a make-up-air system, then you know that your contractor is full of it, when they are (for example) trying to sell you a 300CFM solution. Use all resources available to you!
@AB: First, all the air removed from the kitchen by the vent hood has to be replaced. The hood cannot vent more than is replaced. The house will not implode. If replacing the air requires the interior pressure to fall, the risk is back-drafting combustion appliances, or moving to the left on the blower's fan curve until nearly no hood flow results due to the pressure loss. So balance is always achieved some way. The gamut of kitchen hood blowers are not capable of lowering the air pressure enough to equal a serious hill, much less halfway up Mt. Everest.
So the answer to your first question is "yes." The only way around this fact of life is a (well filtered) recirculating hood, and available models may not meet one's performance requirements, depending on various factors.
The makeup air is required for tight houses but if you live in a loose house like me there is no chance that exhaust will pull from the water heaters and hvac in the garage. I live in CA and our house is old and all the windows leak. So the house breathes. If you live somewhere cold and your house is sealed up, you will need make up air.
We fully agree that homeowners should do extensive research including the use of Houzz and other social forms
But that also should in our opinion includes speaking to licensed professionals in the supporting fields for their project
And that is exactly what we did And we did meet with licensed Structural Engineers , Hvac, general contractor, Electricians and plumbers etc. Every one of them as well researched from their licensing to customer reviews/feedback
Houzx is a great form to use but again you don’t really know the background of the people you’re speaking with and their opinions are worth noting but should be validated
There comes a point in our experience and knowledge that we have to bow out because we are not professionals in this field
Anybody who takes offense to our bowing out should not ...we know limits and cannot provide more than we already have.
Please start another strand for future questions as we will not be commenting on this any further.
So, I wonder where I filed my "social forum" comment license?
Thanks for all the replies.
I spoke with contractor and he referred to wolf/sub zero store rep who works with contractor.. I emailed him and didn't hear back. I guess both of them have no answers!
AB: Call SubZero/Wolf directly with questions about their products. They do answer their phones.
If you want make-up air answers somewhere other than here, then maybe Broan or Fantech will be able to help, or a contractor that deals in commercial HVAC.
Or you can read a dozen pages into this blurb for perspective. The presently functioning link is: https://www.tagengineering.ca/wp-content/uploads/2015/02/KVSApplDesign_catalog.pdf