# Forum Home Renovation Kitchens  Ducting for rangehood requirements

## bennyddd

Hi all, just wondering whether rangehood ducting has to be ducted out of the house via roof or wall as per building code these days? Or whether we can just duct it into the ceiling? Any help would be appreciated ... Also I'm Tassie if this matters. Cheers

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## Cecile

Do not, under any circumstances, duct it into the roof space.  There's an Australian Standard that covers installation of range hood ducting.  Also, the amount of crap that it would deposit onto the insulation and roof timbers is not only disgusting, it's a fire hazard.

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## GDOG

From my understanding, if you have a gas stove, it needs to be ducted out the roof (unless backed on to open, well ventilated external wall, may be wrong here)and with an electric stove either out the roof, wall or eave.  Not ideal sending all that steam and oily smoke into the ceiling.  Let alone Gas fumes. Can not do anything any good especially after 10-20 years.    
Saying that it seems to be a common trend among home owner rangehood installations. That as well as canopy models falling from their plasterboard fixing.  However, if using a gas stove, I'd advise its flued correctly for obvious reasons

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## OBBob

Not sure if it's a building code requirement but you should get it outside. This may start a debate (again) but ducting into the roof cavity is potentially a fire hazard. That said ... I removed a 20 year old kitchen a few months ago and it turns out the range hood only ever vented into the wall immediately behind it!  :Shock:  
Is it difficult to get to the outside?

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## bennyddd

Thanks for the info guys, probably not that hard to duct it to the roof but just trying to be stingy and save some $$$. I have a roofer friend I might contact him for a chat. 
Wow ducted into the wall behind only sounds pretty dodgy, it's funny the things they used to get away with in the old days... My bathroom we pulled out had no water proofing at all but the hardwood floors were pretty much intact.  
Cheers

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## PlatypusGardens

Hmmm pretty sure ours is just in to the roof space.   :Unsure:

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## Moondog55

> Hmmm pretty sure ours is just in to the roof space.

  Yes but just because it *was* common practice doesn't make it correct or sensible.
Evil Step-Daughters place has over 20 years of rancid mutton fat saturating her roof space and ceiling insulation and removing it is going to be a nightmare

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## PlatypusGardens

> Yes but just because it *was* common practice doesn't make it correct or sensible.
> Evil Step-Daughters place has over 20 years of rancid mutton fat saturating her roof space and ceiling insulation and removing it is going to be a nightmare

  
Well I realise it's not ideal. 
Hmmm so what would be a good option, considering it's almost in the center of the house?
Add some ducting and lead it up towards the whirly bird?

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## OBBob

Just order pizza ...

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## Moondog55

> Just order pizza ...

  ROFL 
Can you fit another fan ?
'Cos if you can and you can find some good duct; running the duct up to a whirlybird with an extra fan sucking might work, or just add another whirlybird

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## Eden

out the eave can be a good solution as it removes the chances of leaking roof around the cowel. 
you can put a plastic wall vent cover that has the 125mm or 150mm ducting flange built in. 
food for thought

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## bennyddd

Good suggestion!

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## arms

> ROFL 
> Can you fit another fan ?
> 'Cos if you can and you can find some good duct; running the duct up to a whirlybird with an extra fan sucking might work, or just add another whirlybird

  exhaust must be fully ducted to the outside atmosphere ,not close enough is good enough .

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## Marc

> Well I realise it's not ideal. 
> Hmmm so what would be a good option, considering it's almost in the center of the house?
> Add some ducting and lead it up towards the whirly bird?

  I wouldn't go in the whirly bird.
 If you have tiles, you can buy a patch that replaces a tile and you can fit a short 100mm duct to it. If you have a straight roof, go out from the gable. Metal roof, buy the stuff they sell to seal the flue. 
And don't do like i did and used PVC pipe. It has to be metal. 
My plumber son in law open the kitchen cabinet the other day and saw the duct and asked, who installed this?
Me: I did!
Uh hum I see hehe good job, but it should be metal. ha ha 
Oh well, I am not going to change it _now_​ ...  :Smilie:

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## PlatypusGardens

Yeh it's a pitched tin roof. 
What's this thing "to seal the flue" you speak of?

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## arms

> I wouldn't go in the whirly bird.
>  If you have tiles, you can buy a patch that replaces a tile and you can fit a short 100mm duct to it. If you have a straight roof, go out from the gable. Metal roof, buy the stuff they sell to seal the flue. 
> And don't do like i did and used PVC pipe. It has to be metal. 
> My plumber son in law open the kitchen cabinet the other day and saw the duct and asked, who installed this?
> Me: I did!
> Uh hum I see hehe good job, but it should be metal. ha ha 
> Oh well, I am not going to change it _now_​ ...

  ducting doesn't have to be metal ,any material can be used as long as its static resistant .to fix the pvc pipe just earth the pvc to a metal earth somewhere in the roof cavity .

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## r3nov8or

> ducting doesn't have to be metal ,any material can be used as long as its static resistant .to fix the pvc pipe just earth the pvc to a metal earth somewhere in the roof cavity .

   I thought it needed to be metal (the expandable spring coated in foil is easy to use) because it's all about ensuring flames are vented to the atmosphere in the case of a stove top fire.

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## cyclic

> Yeh it's a pitched tin roof. 
> What's this thing "to seal the flue" you speak of?

  Dektite collar with screws and silicone

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## phild01

I ducted directly into the mouth of a whirlybird, the exhaust can't go anywhere but out.  It sure does spin when when on the highest setting.  It also serves to exhaust roof heat.  What is the issue using a whirlybird like this?

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## PlatypusGardens

> Dektite collar with screws and silicone

   :Confused:

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## GDOG

> I ducted directly into the mouth of a whirlybird, the exhaust can't go anywhere but out.  It sure does spin when when on the highest setting.  It also serves to exhaust roof heat.  What is the issue using a whirlybird like this?

   I would imagine that now that the whirly bird exclusively hooked up to the rangehood not only have you lost its effectiveness from removing hot air from the roof space but its constantly sucking up through the rangehood filters 
No need for the fan though I suppose.  Great $ saver

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## PlatypusGardens

> I ducted directly into the mouth of a whirlybird, the exhaust can't go anywhere but out.  It sure does spin when when on the highest setting.  It also serves to exhaust roof heat.  What is the issue using a whirlybird like this?

  
Did you seal it or is it just sitting under/in the whirly? 
I would have thought sitting a 100-150mm foil duct inside the much larger mouth of a whirly would be ok?

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## phild01

I suspended the expandable metal flue up into the throat of the whirlybird with a surrounding air gap.  That it also sucks air out doesn't worry me as it is a means of keeping a small level of air circulation, and something I don't notice anyway.  I don't like the concept of having a house fully sealed up.

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## PlatypusGardens

> I suspended the expandable metal flue up into the throat of the whirlybird with a surrounding air gap

  
Yeah....sounds good to me....   :Unsure:   
Part from it maybe not being "legal" for some reason, why is this not a good idea...?
anyone?

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## arms

> I ducted directly into the mouth of a whirlybird, the exhaust can't go anywhere but out.  It sure does spin when when on the highest setting.  It also serves to exhaust roof heat.  What is the issue using a whirlybird like this?

  
grease can build up on the blades ,thus eliminating the fluing to the outside atmosphere .

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## Moondog55

> exhaust must be fully ducted to the outside atmosphere ,not close enough is good enough .

  Yes I do know that and that wasn't what I meant to him to do; the extra fan should. of course be fitted inside the ductwork and the whirly bird
It's because in many cases a whirlybird is much cheaper than a new silicon boot of the correct size and also because 2 fans running in tandem are much stronger

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## arms

> Yes I do know that and that wasn't what I meant to him to do; the extra fan should. of course be fitted inside the ductwork and the whirly bird
> It's because in many cases a whirlybird is much cheaper than a new silicon boot of the correct size and also because 2 fans running in tandem are much stronger

  regulations do not stipulate that exhaust air must go through roof ,merely to outside atmosphere .there are a lot of modestly priced soffit vents on the market that adapt to exhaust ducting.
also the cost of the electrical work required to run two fans in sync will far outweigh the cost of a dektite .

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## GDOG

I thought a gas stove needs the flue to go straight up out through the roof if not on a clear external wall.   Can't have any horizontal areas in the flue to hold any gas pockets if the stove doesn't ignite or goes out.

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## arms

> I thought a gas stove needs the flue to go straight up out through the roof if not on a clear external wall.   Can't have any horizontal areas in the flue to hold any gas pockets if the stove doesn't ignite or goes out.

  looking at the ops title it asks about rangehood requirements .

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## Marc

PG, yes, Cecil has the technical name for it. That thingy you buy to seal the flue at barbecues galore.  :Smilie:

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## Marc

So it does not need to be metal? I thought it was a bit overkill, after all the cabinet above the stove is wooden isn't it?
Kitchen grease fumes in the whirly bird ... well, nothing wrong besides the mess it makes. Once it is all coated in oil and dirt, you need to dunk it in sulfuric acid to clean it.

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## phild01

Marc, do you have a tub with sulphuric acid??!!  :Cool look:  :Sly:

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## PlatypusGardens

> Marc, do you have a tub with sulphuric acid??!!

  
Would you be surprised if he did?

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## GDOG

> looking at the ops title it asks about rangehood requirements .

  Yep, which is why I mentioned what I believe to be the gas stove ducting requirements.

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## GeoffW1

> Yes but just because it *was* common practice doesn't make it correct or sensible.
> Evil Step-Daughters place has over 20 years of rancid mutton fat saturating her roof space and ceiling insulation and removing it is going to be a nightmare

  Yes, 
It brings rats as well. 
No cheers in that

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## Marc

> Marc, do you have a tub with sulphuric acid??!!

  Not a tub but have a couple of one litre bottles left over from some experiments we did some years ago. Highly concentrated too, would eat through anything. Whirlibird would last full 10 minutes in it if coated in oil ...  :Smilie:

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## eek

There are different minimum height requirements for electric/gas rangehoods. Also, venting outside is quite simple. Roof space is dodgy. At least it's better than my friend's one that vents directly into the cabinet above :/ 
You can buy flue/flue kits from Bunnings, or order them online etc.  Can get tiled/sheet metal versions. I installed a sheet metal version to vent mine. Hardest part was cutting a circle in the zincalume roof 5m up especially since I have a great fear of heights.

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## r3nov8or

Good discussion here http://forums.whirlpool.net.au/archive/2218452 
Long story short, ducting to atmosphere is not required for domestic kitchens. I'm just the messenger...

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## OBBob

> I'm just the messenger...

  Lol ... wise words from an experienced contributor.

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## dinosour

Be cautious with Flexi duct, we did it a sons house and it only lasted half an hour when it burst. Replaced it with heavy duty pvc. Still going two years on.

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## phild01

> Be cautious with Flexi duct, we did it a sons house and it only lasted half an hour when it burst. Replaced it with heavy duty pvc. Still going two years on.

   Metal or plastic flexitube?

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## intertd6

> Good discussion here http://forums.whirlpool.net.au/archive/2218452 
> Long story short, ducting to atmosphere is not required for domestic kitchens. I'm just the messenger...

  From memory I think you will find that it may been revised to include domestic kitchens. addditionaly its covered in AS3000 which states in a matter of words to the effect  that electrical items have to be installed to manufacturers recommendations, (I havent seen any that recommend pumping grease into a ceiling space with no known outlet relief size or a duct terminating in a closed space)  & AS4386 which deems it a fire hazard. This subject was done to death a few years ago on this forum. 
inter

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## r3nov8or

> From memory I think you will find that it may been revised to include domestic kitchens. .... This subject was done to death a few years ago on this forum. 
> inter

  So on one hand you think it may have been revised since the Whirpool discussion in Feb 2014, but on the other hand it's been done to death a few years ago here.. so 2012? How then can 2012-ish discussion be relevant at all?    

> ...I haven't  seen any that recommend pumping grease into a ceiling space with no  known outlet relief size or a duct terminating in a closed space)  &  AS4386 which deems it a fire hazard. ...

  I have easy access to the end my flexible pipe and there is not a skerrick of grease, oil or any moisture at all accumluating at the end of the pipe. I totally agree that these should be ducted to outside, but there appears to be no clear answer for any point in time over the decades or recent years, and when it comes to insurance etc the date of install and the rules in place at that time are the ones upon which the install would be judged.

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## Cecile

Slightly off topic, but a clear indication of the effectiveness of ducting to outside: 
Our new range hood is 1200w x 700 deep, 850 from the cooktop.  Ted was thinking that he could not smell anything cooking in the house, but the minute he went outside there were delicious aromas in the driveway.  It's a clear indication that Australian Standard or not, wherever you terminate the duct will also be wherever cooking steam, grease, and anything else is deposited.

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## OBBob

^ nice! A good test is to release the steam from a pressure cooker near the rangehood and see how effectively it's captured.

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## r3nov8or

Of course a high majority of the nasties would be getting filtered out by the, errm, filters.

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## r3nov8or

I'm also concerned Ted didn't know he was in fact cooking  :Eek:

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## Cecile

> I'm also concerned Ted didn't know he was in fact cooking

   :Burnt:  :Burnt:  :Roflmao:  
"It's not burnt, it's caramelised."

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## intertd6

> So on one hand you think it may have been revised since the Whirpool discussion in Feb 2014, but on the other hand it's been done to death a few years ago here.. so 2012? How then can 2012-ish discussion be relevant at all?   
> I have easy access to the end my flexible pipe and there is not a skerrick of grease, oil or any moisture at all accumluating at the end of the pipe. I totally agree that these should be ducted to outside, but there appears to be no clear answer for any point in time over the decades or recent years, and when it comes to insurance etc the date of install and the rules in place at that time are the ones upon which the install would be judged.

  It's rare occasions where a rule/law  is made which is retrospective, domestic fire alarms are one. But for the present ducting of domestic kitchen range hoods into roofs or similar closed spaces is not allowed from the interpretation of the 2 standards I quoted.
I'm only the messenger. 
inter

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