Internal, inline and external range hood blowers

There are three basic forms of range hoods blowers:

• Internal range hood blower - the range hood blower is located inside of the range hood canopy
• Inline to the duct run - the range hood blower is located somewhere along the range hood exhaust ducting
• External to the range hood - the range hood blower is located either on the roof or on an external wall

Internal range hood blower

External range hood blower

Inline range hood blower

If the cooking equipment - the stove or the range dicatate (based on the btu to cfm calculation that can be found on posts in this blog) that around 600cfm is required then there is not a great deal of benefit to be achieved by placing the range hood blower remote from the range hood canopy

Noise is one of the main reasons why remote blowers for range hoods are installed. If the range hood blower, whether inline or external is close to the range hood very little benefit in term so of noise reduction will be achieved.

An external blower mounted on the wall directly behind the range hood without any bends in the duct run will not help the noise a great deal.

For optimal noise reduction from an external blower there should be at least one 90 degree bend in the duct run.

For optinal noise reduction a duct silencer system can be placed in the duct run.

Duct silencers

What the Home Ventilation Institute(HVI) has to say about range hoods

PS31 SP Textured Black

 

Kitchen Range Hoods:

A kitchen range hood must move more air than a bathroom fan. about 50 to 140 L/s (100 to 300cfm) as a minimum. As a result, they are noisier, with the lowest rating about 4.5 sones, although they can be

relatively quiet on low speed.
The most useful units have a low noise rating, an energy-efficient fan, fluorescent lights, sound
insulation, anti-vibration mounts and duct connections. For heavy duty use, select non-corrosive
materials such as aluminum or stainless steel. High quality hoods may have heat sensors and a
safety shut-off.
Kitchen exhaust systems should discharge outdoors. Recirculating range hoods rely on filters to
capture some odours and grease. The filters are generally made of carbon which must be
replaced frequently to be effective. Grease will coat carbon, making it ineffective. With
recirculating fans, cooking moisture and odours will usually remain in the house.

Positioning:

Range hoods are most effective when they extend out over the stove surface and are close to the
stove top. Island units are less effective than wall units.

Cleaning:

Range hoods usually have washable, aluminum-mesh grease filters. Better quality filters have a
smaller diameter mesh over a larger surface area and can be cleaned in the dishwasher.

Fire:

There is always the possibility of a grease fire with a kitchen range hood exhaust. Smooth metal
ducting, preferably galvanized steel, is safer in a fire than lighter assemblies.

Installation:

Install fans and exhaust systems so they make the least possible noise, vibrate as little as possible
and leak as little air as possible.
Anti-vibration pads or foam tape can isolate the fan housing from wood joists and drywall. You
can wrap fan housings and some duct sections in rubber or vinyl noise barrier mats.
DuctsInstall exhaust systems according to the building code and manufacturer's recommendations.
Straight, short duct runs, with few turns, will result in the highest fan flow

Range Hood Width

The range hood should as a minimum cover the width of the range. The reason for this is that the hot vapours from the range expand as they billow up. Under ideal circumstances the range hood should be wider than the range by 3" either side - however this is not always possible.

Wall Range Hoods:
Wall range hoods should as a minimum be the same width as the range top

Island Range Hoods:
Island range hoods should as a minimum be 6" wider than the range top. The reason is quite logical - island range hoods are exposed to cross drafts in the kitchen from ventilation systems and even people moving around.

Here is a picture of a 12' wide range hood - the range top is a 30" induction cook top and we provided a 600cfm internal vent blower with stainless steel mesh filters directly over the induction cook top - 30" wide. The remainder of the island range hood underside was custom fabricated stainless steel panels with lighting. The lighting is controlled by two dimmable range hood light controls - one controlled the kitchen hood lighting above the induction cooktop and the other rangehood light controlled the island rangehood lights on the perimeter:

Link to range hood design information

Why does your range hood need a make up air system

What is make up air for range hoods

High cfm range hoods take out large volumes of air from the building space. If this air is not replaced at the same rate that it is expelled, the building will experience a negative pressure (the air pressure outside the building is greater than the air pressure inside the building).

A few common indicators of a negative air pressure problem are:

• Exterior doors are hard to open
• Drafts around doors and windows
• Range hood may not be drawing vapours properly
• Smoke from a wood burning fireplace is pulled into the room

PS11 Custom Range Hood Oyster White with Stainless Steel Trim

A make-up air system replaces the air that is expelled by a building's exhaust system, maintaining the proper balance between inside and outside air pressures while also providing many other benefits:

• Provides conditioned air back into the home - cooled in summer, warmed in winter, de-humidified
• Aids the proper functioning of range hood exhaust fans
• Improves air quality
• Stops backdrafting of fireplaces, natural gas fired furnace and hot water tank exhausts

In the colder northern hemisphere where the windows and doors are closed through the winter and where the homes have become increasingly air tight building inspectors are paying more attention to the need for make up air where high powered range hoods (some areas as little as 600cfm) are installed.

Over the range microwave hoodfan vs range hood

What are the differences between an OTR vs a dedicated range hood.

Over the range micorwave:
 PRO'S:

• Saves space in small kitchens where counter top space is limited
• Its convenient location above the stove
• CFM (cubic feet per minute) is low - limits negative air pressure in the home

CON'S:

• Typically very noisy as a hoodfan
• Does not provide coverage over all cooking elements - so vapours from front burners are'nt captured
• Poor grease filters
• If vented externally then ducting is typically small and cfm is low - not a good situation if being used over say a gas range
• CFM - cubic feet per minute of airflow is typically low - this is okay if over say a basic 30" electric top
• Most OTR's are re-circulating and require constant charcoal filter replacement
• Very low height over the range - "sort of" in your face
• Typically difficult to keep clean because they are so close to the range top and get greasy quickly

Range Hood:
PRO'S:

• If installed and sized to the range correctly these range hoods provides optimal extraction and disposal of those dangerous cooking vapours
• Range hoods are typically visually appealing and enhance the design and look of the kitchen
• These range hoods are easy to clean and the range hood filters come out easily for cleaning

CON'S:

• Range hoods require a dedicated space above the range
• A half decent range hood generally costs more than a good over the range microwave

Our latest happy customer

Ken and Charmaine love their new range hood as much as they love their new kitchen

PS15SP 54" wide by 28" high Oil rubbed bronze with

brushed stainless steel trim and a 1000cfm externally

mounted blower 

Basic builder version under cabinet hood

A common situation we come across is new homes with the basic builder version under cabinet hood. Consumers mostly say the following:

• Its noisy
• It doesn't capture the smoke or vapour
• Its difficult to keep clean
• Grease accumulates on the cabinets around the range hood

Why do these problems exist:

• Builders are under pressure to keep costs as tight as possible - unless you request otherwise and pay for it they will install the most financially economical range hood they can
• The range hood has a $5 blower installed that probably draws between 100cfm and 300cfm
• The grease filters are aluminum mesh that has large holes in them - low density of mesh - saves money
• A combination of poor cfm/suction power and filters results in these problems

Here's your typical builder version range hood filter

Here's a picture of your typical 3 speed rocker switch under cabinet builder version range hood:

Dont get me wrong - i am not knocking these range hoods or the builders - i am merely pointing out that you get what you pay for.

So how do you resolve this issue as a home owner.

• Find out what duct size has been used and what type of ducting has been used
• Once you know this you can decide to use the existing duct work for a new range hood or modify this ducting to that which is suitable for the cfm your range requires which in turn drives the cfm capability of range hood you should have
• Establish the width available for a new range hood
• How high must the new range hood be to ensure that gap between the range and range hood is 30" to 34"
• Will there be unfinished cabinetry if you remove the existing range hood
• Research the market for an under cabinet range hood that will do the following
• Have adequate cfm for your range
• Requires a duct size that you can accomodate
• Is of course the correct width and height and depth to cover the heat elements on the range

Below features of a range hood solution we typically offer clients with the above situation:

PS1010 under cabinet range hood

• 304 stainless steel construction or powder coat colors of your choice
• Stainless steel baffle filters for optimal grease collection - 92% efficient
• Variable speed range hood blowers - 400cfm, 600cfm and upwards
• Dimmable halogen lighting
• 7" or 8" vertical duct take off
• Easy to install



 Follow the link for a detailed specification sheet of this under cabinet range hood solution

Canopy range hood inserts and liners

Canopy style range hoods are still popular in kitchens. There is confusion amongst consumers and sometimes trades people as to the distinction between a liner and an insert.

• A range hood liner is a metal plate of box that covers the exposed surfaces on the underside of the range hood canopy - its purpose is to protect combustable material that is exposed because the insert(the functional range hood component) does not cover the underside of the hood wall to wall - this is nearly always required when using stock or out of the box range hood inserts - btw code generally dictates that there may not be combustable material(wood) closer that 30" to a gas stove burner.
• A range hood insert is just that - its the functional part that inserts into the underside of a range hood canopy. Now if you have an off the shelf insert you will also generally require a liner of some sorts - this liner will need to be cut to allow the insert to fit into the cavity.



The component in the center is an insert - the flat material around it is a liner



At Custom Range Hoods we supply inserts that can be fabricated wall to wall by our supplier Modern Aire Ventilating - this has a few benefits:

• The baffle or mesh range hood filters are extended over a wider area and therefore less cooking residue is collected on a liner
• Bigger filter capture area combined with the best range hood blowers available ensures excellent vapour collection and disposal
• Installation is simpler and less expensive  - 1 component instead of two

 
These come in different styles:

• Mantle style hoods are basically rectangular in stucture and typically anywhere from 14" to 18" in depth
• These do pose challenges for effective ventilation especially over pro style stoves or ranges because there is not full coverage over the burners and vapours bleed up over the front.
• A partial solution is ensuring that the range hood blower is stronger than required to create high suction/negative air pressure around the filters
• The downside of this is excessive airflow noise due to the volume of air passing through the filters

A 14" deep by 72" wide insert into a mantle hood

• Stone or wooden hoods with inserts
• These are becomming very popular and from a ventilation standpoint pose no problems provided there is full coverage over the burners and the insert used has appropriate filters - ideally baffle style filters and adequate cfm via the range hood blower 

Welcome to our latest displaying dealer

We are pleased to welcome Northern Living Kitchen and Bath - owned by Nancy Fournier as a new displaying dealer for Custom Range Hoods. Northern Living have a great reputation in the Muskoka's as evidenced by a personal testimonial from Sarah Richardson on their website. We all welcome Nancy and her team and wish them all the best adding value to their clients kitchens with custom range hoods. Here is a picture of the hood in their showroom:



  Norther Living can be contacted via the link above to their website.

Does your range hood perform as well as it should

Here are a few of the typical issues that consumes encounter with their range hoods and a brief look at why these issues may exist:

Problem = NOISY RANGE HOOD
Result = You don't use the range hood and the grease, vapors are spreading through your home

• The ducting is restricted
• This could be as a result of a back draft damper flap that is jammed in place creating back pressure on the blower - like all things in nature the blower responds and pushes back by increasing its effort
• The ducting is to small for the range hood blower
• Same situation as above - the rangehood blower works harder to get push the air out
• Filters are blocked - usually the case with mesh filters where the grease has congealed and the air cannot pass through easily
• Clean the venthood filters - if they are dishwasher safe - dishwasher otherwise by hand with a powerful detergent
• A cheap motor - as with most things in this world there are varying degrees of quality and a badly balanced and cheaply built range hood blower will make a great deal of mechanical noise

Problem =SMOKE AND COOKING FUMES ARE NOT BEING SUCKED IN BY THE RANGE HOOD
Result = Grease, vapors and odors spread through your home

• Blocked filters as above - this very rarely happens with baffle filters, it mostly happens with mesh filters
• Clean the filters
• The range hood blower system is under powered relative to the stove or range - in ventilation terms it is not drawing sufficient cfm(cubic feet per minute of air) to handle the volume of smoke or vapor being created by the range - very often happens over ranges with bbq's or griddles.
• Not much you can do except change the range hood blower - this has other implications - is the range hood ducting large enough to cope with the increased cfm - there is a correlation between cfm and range hood duct size - see other posts on this blog
• The capture area formed by the range hood does not cover the burners - when hot vapor rises it expands outwards like a funnel - if the range hood doesnt at least cover the burners you will have this problem
• Not much you can do again except a mjor reno and replace the range hood so that it covers the burners.
• A case in point - we were called to a consumers house who had a 48" wide by 27" deep wolf range with bbq - the client loved to bbq. However the hood above the range was only 14" deep - it was/is a beautiful 72" wide custom cabinet mantel hood. This was a big problem - not only are there no inserts on the market that are around 14" shallow by 48" wide there just is not the coverage - we came up with a solution for them - we bulit a custom 14" deep by 72" wide custom insert with baffle filters and only had baffle filters over the 48" space - we then added a 1000cfm external blower to the mix which creates a huge amount of negative air pressure through the filters - not a 100% solution but pretty close - most of the bbq work must be done at the back of the bbq. Picture doesn't show the whole story but there it is.

• Maybe you have a microwavehood - these typically suck in the air and then blow it back into the room - these are called re-circulating hoods - not much to say about these that is positive.

If you have any questions or live with these problems feel free to contact us - we provide advice and suggestions free of charge.

Questions and Answers

Here are some of the typical questions we get on kitchen range hoods and kitchen ventilation in general:
Q.
How often should i clean my filters
 
A.
We always recomend weekly or at least every two weeks. Why so often - well the purpose of the range hood filters is to collect the grease and solid contaminents in the vapor from the cook top. It therefore makes sense that regular cleaning will stop these contaminents from congealing on the filters. Most filters are dishwasher safe. Another tip is to ensure that the filters are "dried off" before re-installing them otherwise water will drip down onto the cooking surface or worse still if the fan is powered up before they are dry it could suck water up into the motor.
 
Q.
How wide should the hood fan or range hood be
 
A.
Ideally the hood should be 6" wider for a wall mount hood. For an island mount hood it is advisable to make the island deeper than the cook top as well - say 27" instead of 24". Earlier we discussed how vapor expands as it rises - thats why we recomend wider. Islands in particular are exposed to cross drafts and this further contributes to the challenge of capturing all those rising vapors.
 
Q.
Are baffle filters better than mesh filters
 
A.
In our opinion yes. Baffle filters are more effective, because of their unique design at capturing the smoke and steam than mesh filters and they are generally quieter than mesh filters. Quieter is really only an issue with high powered fans where we always try to minimize the noise of airflow. They are also more expensive!!!
 
Q.
Why do you need a range hood
 
A.
Cooking creates vapor that is laden with grease, moisture and of course some pretty powerful odors. Without an effective range hood those odors and grease laden vapor will drift through the home and attach to fabrics and surfaces. Allied to this is our homes have become extremely air tight - we dont have our windows and doors open anymore because of the AC or heating system - so all of these bad vapors get absorbed into the fabric, carpeting and onto the solid surfaces.
 
Q.
How Powerful should the exhaust blower be for my range hood?

A.
Typically the manufacturer of the cooking appliance specifies how powerful and how high the range hood should be above the stove. In the absence of this information call the stove supplier or you can use the industry rule of thumb as a guideline - 1cfm of range hood power for every 100btu of cook top output. This formula takes the maximum btu output of the cooktop - assuming the worst case scenario that all burners (gas) are on at the same time. So for example a 60 000btu gas stove top would need about 600cfm. Electric or induction cook tops are a little different - the rule of thumb here is 100cfm for every 10" of cook top - so a 30" electric cook top would need say 300cfm minimum. There are of course other factors involved not the least of which is the ducting. At Custom Range Hoods we offer hoods in 400cfm, 600cfm, 1000cfm and 1400cfm or multiples of these - yes sometimes 1400cfm is not enough - we recently completed a project with a 10' wide hood and 2400cfm external blowers.

Q.
How big should the ductwork be for the range hood

A.
Firstly one should size the duct as a minimum for the cfm that the blower is exhausting. Secondly one must factor in how many bends and how long is the duct run - it makes sense that a 200ft duct run of 6" will be less effective than a 20ft duct run of 6". Bends in ductwork seriously degrade the efficiency of the duct run - for example rather use two 45 degree bends slightly spaced than one 90 degree bend. Finally factor in whether an internal or external blower system is being used - external blowers are more efficient than internal blowers by about 20% - its easier to pull the heavy vapor laden air through the duct than to push it. Now there is as far as we know no scientific formulas or wizadry involved here. So you are now totally confused right - the answer is always oversize the ducting when in doubt - thats all we do - 600cfm = minimum 6" duct ideally 8"; 1000cfm = minimum 8" and 10" would be nice, over 1000cfm minimum 10" duct - or equivalents in rectangular ducting. If you have a really bad duct run and no other way to do it - go with and external blower.

Q.
How high should the range hood be above the cook top?

A.
The hood manufacturers specify this distance in their installation instructions.Code in most provinces or states specify a minimum of 30" distance to a combustible surface - we always advice our clients to set the hood at a minimum of 30" = if the filters get laden with grease because the filters haven't been cleaned for a year - that in our opinion constitutes a combustible surface. No jokes aside - 30" minimum is a convenient height and 34" maximum. Of interest to consider that for every 30" that vapor rises it expands outwards 3" - so if the hood is set at 60", which is totally ineffective, the vapors would have expanded outwards at least 6" in all directions - so the hood would in this case have to be 12" wider than the cooktop

Consumer discussion on magic lung vs baffle filters

Interesting consumer discussion and experiences on magic lung vs baffle filters

Follow this link to read unbiased consumer discussions on the magic lung filter system vs the baffle filter system - we run into this issue all the time with range hood filters - people are sold on the "magic lung koolaid" as someone put it, the less expensive hood and don't appreciate that baffle filters are by far the best form of filtering a range hood:


- Easy to clean

- 96% efficient

- Best fire spread retarder

- Realtively quiet



http://ths.gardenweb.com/forums/load/appl/msg0208411027007.html?22

Baffle filters - capture 96% of solid material



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GZ6Z9PA3YYF7

Remote range hoods blowers

Remote range hood blowers – also referred to as external or inline blowers

The majority of range hoods have the blower located inside of the range hood itself – internal blowers.

Internal Blower

Typically a remote blower is called for when a high cfm unit is required because the stove or range dictates it – link to blower sizing.

Exterior blowers are installed either on the roof or an external wall. Installing an external blower directly behind the range hood has limited value in reducing range hood noise – ideally there should be a bend in the duct run between the range hood and the exterior blower and it should be at least 10 feet distant from the range hood.


 

External Blower Fantech



 

External Blower Abbaka



Inline blowers are installed in the duct run – as far down the end of the duct run as possible. These are a great option for efficiency and noise abatement provided an inline silencer is used – the inline range hood duct silencer works in very much the same way as a car muffler does. An important element in inline blower installation is to ensure the ducting is well secured to eliminate duct vibration.

Inline Blower

Remote range hood blowers are more efficient than interior blowers purely because it is easier to pull air (as a result of creating negative air pressure in the duct) than it is to push air – this of course pre-supposes that the duct sizing is correct.

Due to structural restrictions, such as a range hood being on an internal wall it is not possible to vent directly outside with a short duct run and less than 2 elbows – no matter what size blower is recommended for the stove it is recommended that a remote blower be used – the reason being of you have a complex and long duct run an internal blower will be very noisy even on the lowest speed setting because today’s high efficiency actually pick up their work rate when they sense high static pressure in the duct run – resistance. This then of course leads to duct size issues – the beauty of remote blowers is that they typically require smaller duct sizes than an equivalent cfm internal blower

What you need to know to install range hood ducting

Firstly we need to understand a critical element in range hood ducting – static pressure in the kitchen hood duct configuration

Follow this link to the author for additional useful range hood installation information

Static Pressure:
Inside every duct, there is a constant pressure being exerted at any point from all directions. When a range hood fan moves air through the duct, the air counters resistance from this pressure which is known as static pressure. Thus, kitchen venthood fan has to have the ability to overcome the static pressure in a duct so as to effectively duct stale air to the outside of your home. This can be done by calculating the equivalent duct length of any duct for the range hood ducting.

Calculating Equivalent Duct Length (EDL):
Simply measuring the length of a duct is not enough to know how much static pressure an exhaust fan has to overcome. Ducts may have one or more elbows, turns, or wall caps which add to the static pressure in a duct. Thus, you have to calculate the equivalent duct run and not the actual duct run so as to size an exhaust fan properly.

The static pressure in any duct run differs according to the material of the duct, number of elbows and turns, exterior wall cap and wall jacks etc. Listed below are the standard values for different duct components.

• Smooth metal duct:
• Actual duct length x 1 (eg. 3ft of duct = 3EDL

• Flex aluminum duct: Actual duct length x 1.25 (for 4”diameter duct)
• Actual duct length x 1.50 (for 6”diameter duct)

• Insulated flex duct: Actual duct length x 1.50 (for 4”diameter duct)
• Actual duct length x 2.00 (for 6”diameter duct)

• Wall caps/roof caps/back draft dampers: 30 feet for each cap (for 4”diameter duct)
• 40 feet for each cap (for 6”diameter duct)

      

• Elbows and turns: 15 feet for each (for 4”diameter duct)
• 20 feet for each (for 6”diameter duct)

For example assuming 6” ducting for the kitchen range hood:

 A rule of thumb is that a duct run for a range hood should not exceed 100EDL


Using the above values, you can calculate the equivalent straight duct length that an exhaust fan has to overcome so as to push stale air outside your home and counter static pressure effectively.

Range Hood Terminology

Common Range Hood Terms

A very common term used in ventilation is cfm – cubic feet per minute – this typically measures the volume of air that the hood can process in 1 minute and is an important metric in sizing the ventilation to your particular cooking environment.make up air. In the North of our great continent our new homes are almost 100% airtight – we make them so to keep drafts out. In the middle of winter everything is shut tight – we are cooking up a feast and we have our hood fan running on maximum and its sucking out 600cfm – that is 600 cubic feet of air every single minute – if our home is airtight where is the replacement air coming from – there is only one place it can come from and that is the exhaust pipes used by our furnaces, water tanks and fireplaces that are working at expelling carbon dioxide and a ton of other lethal gases – the result is that we fill our house up with poisonous gases – there have actually been a few deaths from this. The only way to combat this and still keep our beloved kitchen ventilation is to install a make up air system – a system that replaces the air in a controlled fashion as the range hood sucks it out. This is a pretty complex area and can also get very costly. There is no real regulation on this yet but authorities have set cfm limits that can be used in certain areas – typically very low at that – this is very frustrating for a ventilation person because we must match the cfm to the cooking equipment and if we can’t get enough cfm our whole effort at kitchen ventilation will be futile.More ventilation terminology- British Thermal Units – this is a measure of the heat output of the cooking appliances.Canopy – The decorative exterior of the system – sometimes referred to as a shell and can also be a wooden or stone canopy – see liner below



Duct or Ducting – The pipework that the collected is expelled throughExternal Blower - A blower unit that is mounted on the outside of the home.


Inline blower – a blower that is installed between the range hood and the outside – typically in the duct run

Liner or Insert - A non decorative range hood that is installed into the underside of a decorative wooden canopyInternal Blower – A blower that is inside the range hood canopy.

You may also hear of a term static pressure – very basically this is like horse power but the measuring and applying it gets pretty complex and is therefore mostly ignored.

Standard range hoods are available in widths of 24, 30, 36, 42, and 48 inches. For normal cooking needs, select a size that will as a minimum match or closely approximate the area taken up by the burners. (With high-performance cooking equipment, the manufacturer may recommend some overlap, perhaps 3 inches or more on each side.)

In deciding how powerful a fan you will need in the range hood, consider three things: the amount of cooking, the type of cooking generally done in the kitchen and the power(know as btu - British thermal unit - a measure of energy for gas or watts for electric) delivered by the cook top. The more frying and steaming that is likely to occur, the higher the cfm (cubic feet of air per minute) you will want handled. Fortunately the ventilation industry has developed a rule of thumb for cfm required - 1cfm for every 100btu's of cook top output - this can be calculated, by looking up in the owner’s manual for your particular cook top, the given btu's of each burner/cooking spot and add them ALL together - this presupposes the worst case ventilation scenario - all burners are on at the same time and running on the highest setting.

Finally we have a relatively new term –

BTU

How high should the range hood be installed

What height do you need?

Determining the proper height for your rangehood is a simple matter as long as you know the height of your ceiling.  Let say for example that your ceilings are 9ft high, that’s 108 inches.  You would then take the total 108 inches and deduct 36 inches for the height of your range leaving you 72 inches.  Then you will need to determine how high you would like your range hood off of your cooktop.  Modern-Aire recommends hanging your vent hood 30-34 inches above the cooking surface for optimal performance, so let’s just say that you have decided to hang it 33 inches above the cooking surface. You have 72 inches remaining, so deduct the 33 inches for the distance between your cooking surface and the bottom of your range hood and you now have a total hood height of 39 inches.

Ventless or Vented range hoods - sometimes you have no option

A ventless hood is the last resort if you cannot find a way to get the fumes from cooking on the range to the outside. While such a hood will trap grease and will kill odors (while the charcoal in the filter is still active - very important - charcoal filters have a limited lifespan) it will not reduce the condensation and smoke caused by cooking. This is especially a problem if you cook with gas that generates a lot of condensation. Depending on how much you cook you may need to replace the carbon filters every 2 - 6 months to deal with the cooking smells.

While it may cost a little extra, over the years you will benefit enormously from a properly vented range hood - you will also save money by not having replace the carbon filters. http://www.customrangehoods.ca/

Range hood Noise and how to manage it

The critical factors in noise reduction are:

-          Type of filters

-          Quality of duct work – appropriate size for the airflow, length and number of bends

-          Quality and size of blower used

Filters:

There are in essence two types of filters – mesh and baffle. Baffle filters are quieter, 96% efficient and excellent fire travel blockers. Mesh are only recommended in lower cfm applications around 400cfm to 600cfm and over electric style cook tops.

Quality of ductwork:

The most critical element is the size and quality of duct material relative to the maximum airflow you try to move down that duct – for 400cfm internal blowers we recommend 7”, for 600cfm internal blowers 8” and 1200cfm internal blowers 10”. Inline blowers between 600 and 1000cfm need 8” duct and external blowers of 1000cfm 8” duct. Rigid metal duct is strongly recommended – flexible ribbed ducting will be noisy because the air is “tripping” of the ridges and makes noise.

The average duct length and number of bends found today is not too much of an issue – if bends and length is excessive then external blowers and more powerful blowers should be used – if a blowers is trying to “PUSH” a high volume of air down a long and wavy duct run the motor needs to work harder and of course will be noisier.

Blowers:

These  come in all forms of quality – the quality blowers have less mechanical noise because they are well made and balanced.

An internal range hood blower

An external range hood blower

roof or wall mount

An inline range hood blower

http://www.customrangehoods.ca/