(Do I cross post this in the Kitchen forum to get additional input? Still learning how this all the forums and subforms work.)

Hi building - you are right about needing MUA. I live in NJ and any hood over 400 CFM is required to have MUA. We just had our 30" Bluestar range installed in our new home and since this is a small kitchen we also went with a 30" Prizer hood with an inline 1200 CFM blower. We were very concerned about the design for the MUA and our contractor had a new foreman who really wasn't familiar with exactly how it worked.

However our HVAC installer was wonderful. He had no difficulty installing the remote blower and MUA. Our MUA vent is on our roof but it's partially hidden by the gable over the garage. Our range is on an interior wall with the laundry room directly behind it. Our hood vents into the laundry room through a soffit above the cabinets over the washer and makes one right turn and exhausts out the side of the house - the entire duct run is only 6'. I am absolutely thrilled with how little noise the fan makes - even on high you could easily have a conversation while standing in front of the range. Is there any way you could have a remote blower or install a Fantec silencer?

There are others here on the forum who can give you expert advice on your install. But I'd also recommend you speak with a good HVAC installer.

edited to add that duct size is crucial - we went with a 10" duct.

You are correct that going down with the vent duct is potentially problematic. Even the best vent hood will leave some amount of grease in the exhaust gases. This grease can slowly build up in the ducts. And if the duct runs downhill, there always is the worry that grease pools and then poses a fire hazard.

Commercial kitchens have grease traps for this reason, and they have to be emptied regularly. In my jurisdiction, the building inspector won't allow that option for residential installations. They want ducts to always run uphill the entire way.

You could check with your building department whether they have similar rules.

Also, if you wonder just how much impact a bend in your duct has, take a look at this article: http://www.energyvanguard.com/blog/secret-moving-air-quietly-through-your-duct-system

You are not going to have quiet. The sheer size alone negates that. You will be moving way too much air, even at a low volume. Your hood will need to be a minimum of 66" wide, and that puts you into rarified and Very Expensive air. Ventahood is probably the best for what you need, but you are going to have to go up and out. No down.

These are thing's that should have been discussed with your architect during the design phase. Solving a problem on paper is a lot cheaper than when you have a giant hunk of wood right where you need to go with a duct.

I have a remote blower on a 54" hood for my 48" cooktop in current house. While the blower is remote, the simple sound of air moving isn't quiet. And that's on low. My unit sits on the roof and it's set back enough that it's not an eyesore.

There will be nothing quiet and nothing cheap. Perhaps engage a commercial kitchen sales person and designer?

And you CANNOT run this amount of BTU down. Why would you fight heat rising, with all the grease being captured?

It sounds like your home is of a high design and quality. You need competent professionals in the design and implementation phase - kitchens, indoor air quality, HVAC - all this needs to work together.

Thank you all so much. This is extremely helpful. Will definitely go up and out now. Hopefully by putting it on the side east wall alongside with the house's rotation will help camouflage it. We do have both an architect and an interior designer to help, but neither have mentioned it. I just started reading about it on these forums. Thankfully we are relatively early in the plans.

- What are the silencers I have read about and how do they work/would they work here?

- Any benefit re:sound to using two smaller liners instead of one big one and only using one at a time when using only one side of stove? Or is this magnifying the cost for no good reason other than sound? (Because I'm assuming I'd then have two runs up and out and two things on the roof because they wouldn't combine to avoid a turn and to ensure proper function? Well, I guess three things on the roof then with the MUA.)

Fantastic info, kas. Thank you!

Does this get substantially easier/less expensive to accommodate if I go down to a 5 feux range that is 39 ⅜” instead? Or because it's going to be used daily and heavily, I'm going to have the same associated costs and challenges to vent properly alongside noise control? (MUA will happen regardless of size. And fyi - the range will NOT be in an island.)

These are the spec differences:

39":

• Choose an overhead canopy with the following optimum* specifications: 48″ wide x 24″-27″ deep.
• Blowers should be rated at 600-900 cfm, with 8″ round ducting, or equivalent. Size should be measured by the style and quantity of cooking, i.e. Asian stir-fry (vaporized grease) requires higher performance blowers than French reduction (steam).
• Non-combustible Hood can be mounted to wall or ceiling 27″-36″ (from hood base) off cooktop. Check with your hood company for specific requirements.

59":

• Choose an overhead canopy with the following optimum specifications: 66″ wide x 24-27″deep.
• Blowers should be rated at 900-1300 cfm, with 10″ round ducting, or equivalent. Size should be measured by the style and quantity of cooking, i.e. Asian stir-fry (vaporized grease) requires higher performance blowers than French reduction (steam).
• Non-combustible Hood can be mounted to wall or ceiling 27″-36″ (from hood base) off cooktop. Check with your hood company for specific requirements.

The actual remote blower is only around $600 or $700 (for a 1500cfm broan) and the fantech silencer is approximately $150 or less . Difference in cost for the range hood from a 48" to a 66" may be a $1000 or so. What will make the largest difference in cost is how elaborate your make up air system will be and whether or not you need it heated. Heating 1500cfm at a 50 degree Delta won't be cheap in either electricity or equipment . When I get a chance I will attach a video showing the noise of a 1500cfm remote blower with silencer

building2017 wrote:

...

- What are the silencers I have read about and how do they work/would they work here?

These are like giant truck mufflers, except designed for various diameter ducts. They have low pressure loss (forget the value but it is a lot less than baffles). Fantech is the source.

- Any benefit re:sound to using two smaller liners instead of one big
one and only using one at a time when using only one side of stove? Or
is this magnifying the cost for no good reason other than sound?
(Because I'm assuming I'd then have two runs up and out and two things
on the roof because they wouldn't combine to avoid a turn and to ensure
proper function?

If only one side were run at a time, then MUA costs could be lower, but where code requires MUA, I am willing to bet a donut that the AHJ will demand an MUA system that can handle both at once. In theory, the sound reduction will be only 3 dB less. Also, when using the central burners, you will still need both systems for capture and containment.

Well, I guess three things on the roof then with the
MUA.

While commercial systems mostly use roof MUA entry, and I use roof MUA entry, the options for residences are wide open and may include side of house entry, or entry into a basement that has an air path access to the kitchen.

With respect to MUA vs. hood flow rate, as Alan & Xiaoxiao wrote the larger sizes require more elaborate MUA systems and a lot more BTU/hr to heat the air. This is less of a fuel cost issue (except for cooks cooking all day long) than a heating system size issue. You may need between 100k BTU/hr and 200k BTU/hr depending on exterior temperature and flow rate. This has to be provided by a large furnace (say blown oil burner with hydronic heating) or large array of electrical heating elements running from house power, perhaps more power than you are presently wired for. And all of this stuff has to be provided with electro-mechanical controls.

If you want the exterior air filtered finer than sparrow size, the filter pressure loss will likely require a blower to keep the house interior pressure drop below the level (0.03 in. w.c.) where combustion appliances (if any or unless separately MUA'd) back-draft and consequently provide gratuitous carbon monoxide. See Fantech for examples of "turn key" (heh) MUA systems with all the components suitable for some configurations.

Check with your building department on the MUA requirements. We were not required to install such a system on a "1200" cfm hood in MA, king of the nanny states. Opening a window when you use the hood is a far simpler, more cost effective, less energy wasteful means of getting make up air for a big hood in a home where it is used only sporadically, cooking a couple meals a day. If you run it for hours a day every day, then yes, by all means you need conditioned MUA. For the occasional 15 min stir fry session it's vast overkill.

With a well-sealed modern house use of sealed combustion gas furnaces and water heaters with combustion air provided from outside is, I think, essential, along with HRC/ERC ventilators.

Since Feb. 4, 2011, (grace period probably until Jan 1, 2012) Massachusetts has used the 2009 IRC as the reference code with NO deletions or alterations to M1503.4. MUA is required now.

Sorry to hear that, it is a truly wasteful and counterproductive requirement. Neither our architect nor inspector ever said a word about it.

Code Enforcement Officers are also known as Authorities Having Jurisdiction (AHJ). This means that they may be empowered to be the final arbiter of code compliance in their municipal territory. If this is the case in Massachusetts, then they can choose to ignore requirements imposed from above that conflict with laws giving them final say, at least until legal precedent establishes a limit on their power.

In other words, it is not unheard of for laws to be in conflict, or for small towns to resent impositions by state governments controlled by city politicians. The centers of government of the original colonies were often deliberately placed far from ports to limit the port cities' power over their state governments. Massachusetts and Maryland are notable exceptions. Of course, modern speed of communication and transport makes this separation politically moot, leaving only a reduced potential influence of big-city mobs as a remaining remoteness advantage.

Legal precedent has been established to limit their power. Policing and enforcement of laws is the jurisdiction of the executive branch of govt. The authority to make laws is reserved for the legislative branch of govt. It has been this way since the constitution was written and the separation of powers was established.

Ignoring laws, and failing to carry out one's job responsibilities is just that - nothing more. It is not some sort of political coup, or legal wrangling.

From the Massachusetts official website.

Meaning, that the inspector can not just ignore the MUA requirement, but if you need 1000cfm of MUA, and the calculations say that the capacity of the MUA duct(s) only provides 990 cfm, then the inspector can say that you do not need to iinstall another duct, making the MUA way over at 1440 cfm.

Notice that this says "enforcing", not "making up".

Other legal precidence and explanations.

I was addressing potential realities of behavior, not what the law and precedent in the Commonwealth of Massachusetts may require, for which I claim no expertise. Examples of "lenience" may make the news when a falling tunnel overhead assembly kills someone, but examples of lenience having little to do with safety are unlikely to be known outside of the group of affected persons.

Separation of powers in the Federal Government, as well as conformance to the Constitution, have been observed mainly by exception. In my view the association, no matter how fleeting, of the US Constitution with Massachusetts laws (or US laws, for that matter) is at a minimum insulting to the Constitution, to those convened to construct it, and to those who took an oath to defend it.

I have no dog in the MA AHJ fight because I don't live there and never will live there. I only have to endure MA subjects escaping their fouled Commonwealth by moving north and then voting the same as they did in MA, thereby progressively reforming NH into the same economic and social disaster area as the one they left.

But this digression may be viewed as hot air flow that is insufficiently within
the capture area of kitchen ventilation, so I'm not going to further
address MA MUA.

"I was addressing potential realities of behavior, not what the law and precedent in the Commonwealth of Massachusetts may require"

"If this is the case in Massachusetts, then they can choose to ignore requirements imposed from above that conflict with laws giving them final say, at least until legal precedent establishes a limit on their power."

.

Frankly, I think you are just talking in circles, just to hear yourself talk. Your writing is not so elequant that nonsensical ramblings about MA are an asset to the OP.