# Forum Home Renovation Kitchens  Rangehood flue DIY to ceiling

## tundra

Hi folks,
Is there any reason I should put some sort of ducting inside the stainless-steel flue of a canopy rangehood? 
I've been replacing the original kitchen in a 50's house (Wasn't much to remove!) and am up to the rangehood.
Am installing a used Qasair steel canopy hood on an external wall. It came with a 10x23x95cm s.steel flue "cover" which is long enough to reach into the ceiling past the insulation.
Its an old house and the roof space is well ventilated with open eaves adjacent , so I was happy to just run the flue into there.  
OK... just got the big blue notice "*Ducting a rangehood into void spaces, ceiling or roof cavities is deemed a FIRE HAZARD." * from the website.
Hard to imagine flames leaping 2m from stove to roof. I suppose it happened once, so we get yet another regulation. 
So maybe I should put something in the roofspace to direct the air over the double-brick wall to the open eaves.  No point putting a hole in the roof in this case is there? 
And should I put something inside the steel flue, or just use it as is?  It is a closed rectangular tube - stainless on 3 sides and galvanised steel riveted on the back.
The hood has a big "DUCT SIZE MUST NOT BE REDUCED" warning, and a powerful centrifugal fan.

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## Master Splinter

What can actually happen is that the inside of the duct gets coated in fatty deposits and dust, which can catch fire from a fire on the hotplates, spewing little burning bits all through the roofspace where they will sit and smoulder.

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## ringtail

I remember putting my range hood in. It came with 3 mt of 125 mm flexible ducting. Since I was more than that distance to the nearest wall I just ran the ducting right up to under a whirly bird with a piece of mesh cable tied over the end. Works great. My rangehood has two filters before the fan motor and I would say it would be near impossible for any flame from the cooktop getting past these. Range hood is 750 mm above the cooktop

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## Godzilla73

G'day, 
Qasair use there own sheetmetal ducting kits for their hoods, check the website. They may have an adapter for a 150-100mm flexi duct to make it easier to vent out the roof. Make sure the flexi stuff is suitable for rangehoods and is fire rated.  Qasair.com.au

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## tundra

> What can actually happen is that the  inside of the duct gets coated in fatty deposits and dust, which can  catch fire from a fire on the hotplates, spewing little burning bits all  through the roofspace where they will sit and smoulder.

  I  just got up there for a look. The roof is full of flamable-looking  dust, fibres  and leaf fragments on top of old fibreglass bats. I  brought some down and attempted to light it.  Would burn but not stay  alight. And its >35deg here today.
But the top of the ceiling where the flue comes through is bare, from the wind blowing under the eaves.
Still don't like the idea of flames up there.   

> G'day, 
> Qasair use there own sheetmetal ducting kits for their hoods,

  Ah - That must be what I have. Thanks. So will conclude there is no need for any of that flexible ducting for me.
I'll add some extra sheet-metal in the roof to guide the exhaust over the wall, so no gunk can accumulate in the roof. 
thanks for the replies.
It is now installed and looking good, except for the splashback. new thread time.

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## manofaus

i put a flapped vent on the outside of the house so that it does not vent into the roof cavity but straight out the side of the house.

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## tundra

HIA says ducting into the ceiling is OK.  Who is right? They, or the big warnings on this website?   

> Many people quote the Australian Standard 1668.2  2002 ... which states that All exhaust air  shall be discharged to atmosphere However the most important thing  with this Standard (as with all Standards) is that you need to read the  whole document to understand when the requirements apply.  
>    AS 1668.2 does cover kitchen exhaust hoods but only rarely applies  for residential buildings and it would never apply in Class 1a buildings

   HIA - Ducting range hoods for domestic use and Australian Standards (Nat)

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## Eden

the hia dont make the law and anything is open to some interpretation  
duct into your ceiling and it may go woof  
a rat chewing elec cable will cause a flame in  a cavity area that is coated in oil and dust mix 
you just dont do it !!!!  
(if it were me ) I would send it out the external wall its mounted on and reap the extra extraction that is lost pushing the air all the way to the roof through the flue system 
good luck 
eden

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## Moondog55

Even if you do sense that the HIA interpretation is correct ( and insurance companies would probably argue that it isn't ) ducting into a roof space is simply not a good idea; it leads to a build up of grease, oils and fats that encourage vermin and if a fire occurs feed the ensuing fire.
The consensus on this forum is that the information in the sticky is correct.

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## BaysideNana

I had a huge fight with the builder about NOT venting the rangehood into the ceiling cavity, he just wanted to end any ducting at the ceiling, this option would have looked awful because of the raked ceiling in the kitchen with overhead cupboards finishing approx 50mm above door height.  His argument was also backed by the kitchen installer (and other tradies working onsite) and I was made to look like a bad person because I demanded it be ducted to the exterior.  Why?....because in a past life I had to get into the roof space of many houses and the greasy, grimy mess that was coated on roofing timbers was horrible and in some cases the smell was just awful, let alone a fire hazard.  Rats would gnaw on the timbers and in so doing would often gnaw on electric cables as well. Many times we were called to inspect roof spaces because an owner complained about a horrible smell coming through downlights, ceiling vents etc and on closer inspection it was found to be the grease-laden timbers which gave off this horrible smell...specially on a hot day with a tin roof above.   
My rangehood is a concealed model and I wanted it vented through the overhead cupboards, then through the exterior wall to the outside via a 125mm vent, just below the eaves and couldn't see why this was a problem?  Ok, I lost 'some' space in a 750mm cupboard which was no big deal and looks HEAPS better because neither the rangehood or ducting is visible AND it's ducted to the exterior.  Even the kitchen installer (after it was finished) commented how much better it did look although neither he nor the builder, would admit it should never have been vented into the roof space.  At that time I wasn't aware of the AS number but knew it was listed.   
In the future, rather than clean the inside of the ducting it will be simpler and easier to replace it with a clean, fresh piece and would only take 10 minutes and all be done from the kitchen.  Too easy!!   
Doesn't help your situation Tundra but might help someone else.

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## tundra

I suppose it depends how you cook.  The last place I lived vented to ceiling, and I never noticed a problem in there.
The standard not so long ago was an exhaust fan  flush with the ceiling or wall, just like in the bathrooms.
Anyway, my new one is now blowing out to the open eaves. 
The answer to my original question is clear enough now. The steel tube _is_ the duct. And it is removable for cleaning.
Thanks folks.

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## Eden

its the same with any risk taking isnt it ?  
he didnt notice there was a problem until the truck hit him!    
this sort of regulatory advice isnt just so you can take the risk if you feel its a load of malarky 
it is also there for your neighbours and anyone else that could also go up in flames  
good luck with the kitchen

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## tundra

Eden, try reading my post again. Your response makes no sense.
I should have said I climbed up in the ceiling and there was no grease build-up of the type others describe.
Further, it was not my home so I had no choice.  And none of that applies to my house now.

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## Pulse

I agree with you Tundra, 
Many domestic rangehoods blow straight back into the room and are not ducted at all, whereas even small commercial kitchens in takeaway stores have serious ducting costing thousands. 
Therefore it all comes down to use, if you love grilling meat inside or stir fry foods then duct it. If you don't it probably does't matter. I remember seeing a house that some asian students lived it at uni where the kitchen walls and top of cupboards were coated in oily crap, My kitchen on the other hand is pretty clean. 
Cheers
Pulse

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## Bloss

mmm "_Hard to imagine flames leaping 2m from stove to roof_."  Cooking ands hot oil on stoves are the second most common cause of house fires in Australia (heating equipment are the first). A fat fire can rise not just 2m, but more very quickly and if there is an exhaust fan sucking those flames then it is easy to imagine the consequence. Google kitchen stove fires youtube and see some fine examples. 
The use of flame resisting mesh has helped reduce that, but I have not vented a kitchen exhaust into a ceiling space in the last 30 years. It adds bugger all to the cost and a huge safety plus IMO. Also allows proper exhausting of smells and if correct sized ducting is used is much quieter too. 
The key is as has been said - and by HIA (and read their disclaimer at the bottom . . .) the rangehood must be installed according to the manufacturers instructions and most nowadays, as you have seen, strongly recommend through roof or wall ducting. IMO for good reason.

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## Eden

> I agree with you Tundra, 
> Many domestic rangehoods blow straight back into the room and are not ducted at all, whereas even small commercial kitchens in takeaway stores have serious ducting costing thousands. 
> Therefore it all comes down to use, if you love grilling meat inside or stir fry foods then duct it. If you don't it probably does't matter. I remember seeing a house that some asian students lived it at uni where the kitchen walls and top of cupboards were coated in oily crap, My kitchen on the other hand is pretty clean. 
> Cheers
> Pulse

  
for systems to be set up "recirculating"  if the instructions are read or if they are sufficient should say to use carbon "filters"   
these clip or twist on inside the unit once the initial external filters are removed 
I have asian clients that change them every 4-6 months as well as cleaning the initial filters monthly 
and i have elderly clients that havnt needed to change them in 5 years  
All I am saying is if you install to roof cavity or into double wall gaps  or other non advised methods  and down the track there is  a fire  they will look for liability and whom installed  or did the work  
cheers

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## Bloss

Never seen a residential recirculating system that actually works . . . commercial ones MUST be externally vented.

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