I'd think an inline blower is low cost.
I got one. I built all the rest around it.

A clarification:
an inline blower IS a remote blower, at least using the standard terminology.

An "internal" blower may be what you're referring to: the fan unit is mounted inside the actual hood.

Remote blowers are located outside of the actual hood. There are two types of "remote" blowers--i.e., fan units that are NOT mounted in the hood itself. Inline blowers are installed remotely, somewhere in the run of ductwork. They are typically mounted inside, in an attic, for example, as ours is. There is then another run of ductwork from the blower to where the exhaust exits the house, on the roof for example. Here's a popular one:

Fantech inline blower

An external blower is mounted on the outside of the house, usually the roof, but sometimes on a wall. Here's an example:

Abbaka external blower

The choice of an inline vs external blower can be complex, and depends on factors including space (is the attic big enough to put an inline blower in?), access (is the roof so steep that it is difficult to mount an external blower?), noise, cfm ratings, etc.

The decision to use a remote blower rather than an internal blower is mainly driven by a desire to minimize noise. Internal blowers can certainly match external blowers for performance, but they cannot match an optimized remote blower setup from the standpoing of noise.

Remote(External) vs. in-line.

Both of these are located outside of the hood. IMO the in-line blower is quieter. Also, an option in the installation allows for the in-line blower to be mounted using links, therefore; there is no vibration noise.

However, keep in mine, moving air makes noise, whether using a remote, in-line, or internal blower so make sure the duct size is in accordance with specs. Also, minimize turns in the duct.

Another key point is the larger the blower, the quieter the operation when on low. Low is the setting used most often.

I had the same questions. Vents, blowers, etc were all confusing. I think you're duct work and space will determine the type of blower. Originally I was going with an prestige in-line 1200 CFM blower ($800). I needed to minimize the viusal impact to the outside of my historic house. The vent could be seen from the street so that's why I planned on an internal blower. Now I totally rearranged my kitchen and will buy a 1200 CFM prestige external blower ($1000) instead. This will be mounted on a side wall in the back of my house. If I was going to do an in-line blower in the latest kitchen drawing than I had to make a "door" in the ceiling to get at the blower if I needed to in the future. The in-line blowers are big 41"L x 21"W x 14" H. If you're worried about noise you can have a fantech silencer in front of the blower - but they're big too. I don't have room for it.

It all depends on the specifics of what models you are thinking about . One style is not clear cut cheaper or quieter. System design will play a big part in it too. If you are serious abotu it being quiet , better enlist help of an experienced designer and check out some installs.

Oh boy. Thanks to all of you for your input but I'm still confused.

Here the specs: We are getting a 36" Wolf with 6 burners, so I'm thinking 18" high, 42" width, under cabinet/wall mount with at least 900 cfm. The range is on an external wall that can vent straight out (no turns in the duct) and not to the roof (2nd floor above). It is NOT important for that exterior wall to look pretty as it faces the back of the garage.

I suppose I'm confused on whether to get a hood that has internal blowers or one whose blowers mount on the outside of the house and what the difference would be. Sorry if I mixed up my terminology. I don't know which one to get for under $2000 Cdn that will not sound like an airplane taking off in the house.

help?!

genie, since you are also in Canada, do check your local building codes to see if make-up air is required. In my jurisdiction, any fan larger than 250cfm requires make-up air, and 600+cfm definitely requires heated make-up air. My 600 cfm system incurred $7K in installation costs that I was not expecting. It made my other fairly high end appliance price tags look insignificant.

Genie typically an external blower, as clinresga quite correctly defined being distinct from an internal blower is typically more money than an internal blower system. There are two components to noise - firstly there will be the airflow noise which is dependant on many factors the least of which is the filter system - good quality baffles will make less noise than a mesh filter, and then of course there is the ducting - restricted ducting will significantly increase the noise because good quality blowers work harder to maintain the airflow called for by the controls. So internal or external blower wont matter much with airflow noise. The second main component of noise is mechanical noise from the blower itself or vibration from an unbalanced motor - here again a high quality blower will have less mechanical or vibration noise noise. Generally most of your ventilation takes place at around 30% or so of blower capacity - you just dont need to crank it up all the time - when you have lots of smoke from say a griddle or steam then you can increase the cfm needed to get the smoke or steam out. So which is better - internal or external - external is a little quieter generally even with high quality blowers but you should weigh up the increased cost of an external blower against the occassional marginal increased noise as a result of mechanical noise when you crank the blower up. The last post by cooksnews is an important one to consider - if you are under permit in certain cities of Canada you should consult the controlling body about make up air - if they require it then with a 36' Wolf 6 burner you MUST have the cfm power because it WILL create a lot of heat and potentially smoke and therefore you will have to do that make up air.

Here is a link that might be useful: Canadian Supplier for Modern Aire

genie73, do you have the latest in air handling and heating systems? A Heat Recovery Ventilator (HRV) or an ERV. What heats your house? What moves air if anything? What year was your house built? Is it leaky or airtight?

For about six months of the year you keep windows closed, so plan where air should come from. Even artisan fireplaces have a tube going outside to get fresh air to have oxygen to burn. Once you go higher than 300 CFM, your biggest problem is figuring out what replaces the air that is supposed to be blown outdoors. Without any new air coming in, on 'high' the blower will work extra hard, straining and making noise, without even managing to get the air in the duct to move much more than "X" (pick arbitrary midrange number here).

Does any one have any real data ? Opposed to irrelevant opinions .

its not that hard . You can buy a DB meter on amazon for like $50 . Then take a meshurmrnt in the kitchen Once inline and once build in , or external .

There is no difference in noise between the Remote, In line, or the internal. The noise is not generated by the blower motor(which is electric). The noise is the air moving through the duct ventilation system through the duct work hence the larger the CFM the more power the more air flow the more noise.

Actually hood ventilation noise consists primarily of two components - blower or blower mechanical noise and airflow noise (ignoring vibration caused from a cheap and poorly constructed hoods).

A low quality blower will introduce mechanical noise hence one should always strive to install the best quality blower you can - each of those blower options below have specific areas of use - an inline blower mounted remotely will reduce immediate mechanical noise versus an internal blower in the hood HOWEVER an inline blower brings its own risks in terms of resonance (air waves from blower oscillations and minute vibrations) in a confined area. An external blower mounted close to the hood is about the same as an internal blower in the hood - one typically uses an external blower if you have a difficult duct run - sucking air from the end of the duct run along a convoluted and long duct run is far more efficient than trying to PUSH air from inside the hood via an internal blower along the same duct run. At the end of the day noise has mainly two components - poor quality blower that introduces excessive mechanical noise (there will always be some but this can be mitigated by using a good quality blower) and most importantly the QUALITY of the duct run - a duct run that is too small or multiple 90 elbows or has been crimped(dented badly at installation) OR using the ribbed aluminum stuff versus smooth HVAC galvanized ducting introduces a lot of air flow noise - of course the type and design of the filtration system also introduces airflow noise in the hood. By far the biggest problem we have found in over 20 years of custom range hood sales and installations is ducts that are far to small for the airflow generated by the internal blower - modern blowers (good quality ones) sense duct restrictions and run faster (more revolutions and therefore more mechanical noise) to compensate and delivery the requested volume of airflow - a simple mathematical calculation will illustrate this - a 6 " duct which everyone believes is adequate provides 28.28 sq inches of airflow capacity whereas an 8" duct supports 50.28 sq inches - nearly double the volume of airflow - so of course an 8" duct is far more efficient and is why we recommend an 8" duct over a 6" for 600cfm and 10" duct over 8" for 900cfm and 1200cfm. An added tip - another benefit of external blowers is that because they are far more efficient at moving air over distances and bad duct runs is an 8" duct is sufficient for say a 900cfm or 1200cfm external blower - qualification of course being a high quality external blower system such as ours - cant comment on the others out in the market - as always you get what you pay for......at Custom Range Hoods we are always willing to help and will assist anyone with technical questions - placing an order with us will of course open the door to a mountain of experience and good advice - feel free to email us at allenl@customrangehoods.ca.

@ed915: At high fan rotational speed, blower blade tip turbulence noise dominates. As the blower is moved farther from the hood, this will slightly attenuate and more of the duct noise will be on the cook's side of the blower. Also, there is more room outside, and often along a duct, for a larger diameter, slower rotation rate blower, and this may reduce blade tip noise relative to a blower internal to the hood pushing the same CFM. If a silencer is used in a (necessarily longish) duct leading to a remote blower, then blade tip turbulence noise is mostly removed, as is downstream (air-wise from the silencer) duct turbulence noise. The dominant remaining noise for a baffled hood will be from baffle turbulence induced when changing the air direction 360 degrees to centrifugally eject larger grease particulates onto the baffle blades.

In my system with roof blower and in-line silencer, the baffle noise might be characterized as a hiss, and normal level conversation across the space under the hood is feasible at full power to the 1500 CFM blower (actually flowing around 1000 - 1200 CFM).

It is also worth noting that if one is going directly out a wall and provides sufficient MUA, then the blower can be operated slower for the same required air flow rate due to low duct pressure losses. This factor will generally be modest though, if one uses the guidance above for duct sizing, or just the general rule that the duct air velocity should be limited to the range of 1000 to 2000 ft/min, with the lower value preferred in cold weather (and in general to lower noise).

And don't forget that the MUA path pressure losses are in series with the hood and outgoing duct pressure losses, and an active MUA can have all of the same noise sources as the hood path.

Excellent technical rendition - hence ideally reduce blower speed as much as possible and ensure ducting is sized correctly and as smooth as possible to enable smooth airflow - an external wall mount blower placed directly behind the hood will have marginally less noise versus an internal blower of equal capability.....ducting is the key element in the noise equation........baffles do add noise but they perform an outstanding job collecting the grease which is critical to ensure minimal grease build up in the duct run or blower system.