# Forum Home Renovation Kitchens  Kitchen exhaust into roof space

## brettsyoung

Hi everyone.  Is there any reason I can't end the exhaust for the stovetop in the roofspace rather than run it up through the tiles?  There is a whirlybird above the kitchen, I have a high-pitched roof, and 11 foot ceilings.  I realise there will be warm, moist air being pumped into the roof but I can't see why this would be a big problem.  Am I missing something? 
cheers
Brett

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## Moondog55

YEP 
That's the short answer, my reply is that it is not the water vapour that will be the long term problem but the build-up of grease and oil which is a MAJOR fire hazard, also it attracts vermin like cockroaches, mice and rats

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## president_ltd

> Hi everyone.  Is there any reason I can't end the exhaust for the stovetop in the roofspace rather than run it up through the tiles?  There is a whirlybird above the kitchen, I have a high-pitched roof, and 11 foot ceilings.  I realise there will be warm, moist air being pumped into the roof but I can't see why this would be a big problem.  Am I missing something?

  yes.
AS/NZS 4386.2:1996

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## seriph1

what they said   :Biggrin:

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## brettsyoung

Thanks Moondog.  Rather obvious once you point it out.

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## Kitchenupdates

> Hi everyone. Is there any reason I can't end the exhaust for the stovetop in the roofspace rather than run it up through the tiles? There is a whirlybird above the kitchen, I have a high-pitched roof, and 11 foot ceilings. I realise there will be warm, moist air being pumped into the roof but I can't see why this would be a big problem. Am I missing something? 
> cheers
> Brett

  Hi Brett
There is no reason you cannot put your exhaust into the roof space ! I have done this many a time
             Cheers Dave

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## Moondog55

Hi Dave, sure you CAN do it, but have you ever attended a house fire??

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## Moondog55

1. BUILDING CODES & REGULATIONS
2. FIRE HAZARD
3. LEGAL OBLIGATIONS - DUTY OF CARE 
4. MANUFACTURE WARRANTY - ( not ducted properly - voided warranty issues )
5. PESTS AND VERMIN CONTROL
QUOTE:  The New South Wales Fire Brigades attended 4,653 home fires in 2005/2006, with 2,174
(47%) starting in the kitchen. http://www.nswfb.nsw.gov.au/about/news/ ... itchen.php
Ducting a rangehood into void spaces, ceiling or roof cavities is deemed a FIRE HAZARD.
Correct venting of rangehoods is a legal requirement specified in AS1668 covering
mechanical ventilation and requires all exhaust air shall be discharged to the
atmosphere.
One should not simply duct the air inside the cabinet without a ducted system as illustrated
in Australian Standard, AS/NZS 4386.2:1996 Domestic Kitchen Assemblies.
It is everyones responsibility, DUTY OF CARE, ( architects, builders, developers and
building inspectors etc ) to see that rangehoods in kitchens are properly ducted either
externally, by using a fire rated ducted system directly to the outside of the building or if
using a recirculating rangehood to make sure that it has an internal ducted system which
is fire rated, this is generally done through the front or side of the bulkhead.

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## president_ltd

> Hi Brett
> There is no reason you cannot put your exhaust into the roof space ! I have done this many a time
>              Cheers Dave

  if you have done so Dave, then you've done so in violation of AS/NZS 4386.2:1996. 
if you do this for a living i hope your professional indemnity insurance is up to date.

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## chrisp

Out of curiosity, can the ducting be made out of DWV or does it need to be metal?

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## PhilT2

Most new homes around here seem to have the exhaust vented direct into the roof space. I have seen older places where insulation around the outlet has become coated wjth a thick layer of grease over the years. 
I didn't want to disturb the tiles so I vented mine out through the soffit.

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## Moondog55

> Out of curiosity, can the ducting be made out of DWV or does it need to be metal?

  Ducting should be fireproof, DWV is usually PVC and quite burnable with nasty off-gassing and dangerous smoke; so I would say not.

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## jago

Vent  outside as all before have said. I would suggest that you use rigid smooth metal ducting the corrugated stuff collects grease aswell. 
Spend the extra now to protect your assest and yourself. :2thumbsup:

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## GraemeCook

> 1. BUILDING CODES & REGULATIONS
> 2. FIRE HAZARD
> 3. LEGAL OBLIGATIONS - “DUTY OF CARE ”
> 4. MANUFACTURE WARRANTY - ( not ducted properly - voided warranty issues )
> 5. PESTS AND VERMIN CONTROL
> QUOTE: “ The New South Wales Fire Brigades attended 4,653 home fires in 2005/2006, with 2,174
> (47%) starting in the kitchen.” http://www.nswfb.nsw.gov.au/about/news/ ... itchen.php
> Ducting a rangehood into void spaces, ceiling or roof cavities is deemed a FIRE HAZARD.
> Correct venting of rangehoods is a legal requirement specified in AS1668 covering
> ...

  
Excellent response, Moondog. 
But you omitted to mention that it would also invalidate insurance. 
Also why would anyone put that greasy mess in their ceiling.  It would quickly stink and seep through the ceiling plaster.  
Cheers 
Graeme

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## Smurf

The vast majority of rangehoods that I have seen vent into the roof space. Not to standard maybe, but very commonly done in practice.

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## Moondog55

Smurf I have seen them sold with out the duct kit too, no salesman is going to blow a sale on a $99- hood by telling you that the ducting to comply with the law is going to cost extra.That said most do come with a box that can go through the wall, even the cheapies I've seen can mount easily on an exterior wall, it is these designer kitchens with the stove and oven mounted in an island that cause the problem I think. Yes it may have been legal in the past but if you retrofit or do a new for old replacement I was under the impression that the replacement hood must be ducted to the outside. 
I personally would never send all that grease and dirt into my roof space, for the reasons already stated

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## Smurf

> I personally would never send all that grease and dirt into my roof space, for the reasons already stated

  Likewise, although it wouldn't bother me too much given that I never fry anything anyway so grease wouldn't be an issue.

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## Moondog55

You would be surprised at how much oil and grease can be carried in a cloud of steam, even if you only stir-fry of braise every group of steam molecules has a very thin coating of oil on the outside, if you can see the steam rising it is at least 1% grease unless it is only water you are boiling of course.
Then when it is warm the water evaporates leaving the oil and fat behind 
I know this because of my trade training and work experience I am a professional cook ( CHEF )

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## pb02

I've just finished renovating our kitchen which had the original rangehood ducted into the ceiling cavity. I ended up tearing down half the ceiling plaster because it was so thick with grease, muck, and mouse droppings... Even found 3 dead mice in the area (previous owners must have been bad cooks..  :Tongue: )
I took my time and re-routed the ducting on the new ranghood outside through a brick wall and finished it off with a nice stainless steel duct cover. Regardless of what the regs say I would never run a rangehood into the ceiling cavity after seeing the mess that I have just removed.

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## Terrian

> Also why would anyone put that greasy mess in their ceiling.  It would quickly stink and seep through the ceiling plaster.

  ummm, coz that is how it was when the exhaust fan was installed 20+ years ago 
and guess what, no sting & no seep through the ceiling plaster. 
Mind you, when the kitchen gets its redo some time in the not too distant future the exhaust will be vented to outside the house.

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## kitchengirl

Hi everyone
Just a quick question - installing a rangehood in recirculating mode is okay though, isn't it?  My understanding is that it doesn't go into the ceiling cavity, but is just recirculated into the air in the kitchen?
Thank you

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## watson

The Regulations mention recirculated mode as being OK.
I'll see if i can find the reference in the morning.

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## peter_sm

I am in the process of designing our kitchen renovation. The 1952 kitchen is cute, but waaaaaay out of date. I see there is a circular fan in the ceiling already, but has not worked in the 5 years we have owned our place. 
I have decided on a rangehood (SWMBO has chosen actually), and there is no question in my mind that an external duct kit is required. I have the choice of roof exit or under eave exit. I will be going for the eave exit for now, and when we get a new roof, I will probably get a roofing one installed, as it would be more efficient to have the duct 100% vertical than have it run 1.5m horizontal to eaves.

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## TomH

Our last house had a recirculating rangehood.  It came through a cabinet then vented at the top of the cabinet.  There was about a 1m gap between the cabinet and then an exhaust fan in the kitchen roof, so effectively the rangehood blew the fumes around the kitchen 
There were a number of major disadvantages in this set-up: 
1.  All cooking smells end up recirculating in your house.  I.e. if you fry fish or sausages, I hope you like the smell.
2. Smoke gets recirculated.
3. Build up of fat on the ceiling, walls and top of the cabinet in the immediate vicinity. 
It took away the steam when cooking, but essentially transported it into another area of the kitchen so I would strongly recommend venting outside. 
Cheers, 
Tom

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## Andy T

I second Tom's comments. My previous rangehood was recirculating. All it did was move the steam and smell around the kitchen and rest of the house. When used on high the updraft somehow caused the steam to bypass the rangehood altogether and blow it in front of the rangehood!!. The ceiling was a mess. My new Qasair rangehood (expensive, but which I am very happy with) specifically stated in the installation manual that it HAD to be ducted outside.

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## Firey05

Great thread. Very good advice has been given in that it should be vented outside to prevent the build up of flammable material into roof spaces/voids etc. 
AS/NZS 4386.2:1996 was written 1996. Prior to this a different standard applied (if any) so no doubt there are installations out there which do not comply with the current standard, but as we know they are not retrospective and are impossible to enforce given the thousands of installations out there which vent into the roofspace or similar and not outside. The reason the NSWFB puts out media releases, such as the one quoted, is to make people aware their home may be at risk and to check and modify current installations. Anyone in the game and still installing in this manner will be in a world of hurt if corners are cut and installations are done on the quick and cheap....... 
Stay with me here........... the reason I posted on this thread........ The fire station I work at (which will remain nameless to protect the innocent) was built around 2004/05. Recently, a rangehood (there is two) needed repair. The repairer discovered the rangehood vented into a cupboard above the rangehood less than 1/2m2 in size, not even into the ceiling. You can imagine what was in there, as firey's can burn and/or destroy food with the best of them, and don't mind a fatty cook up every now and then  :Biggrin: . There is suspicions the other rangehood vents into the ceiling, as you know what someone is cooking (or burning) when you are having a shower 40m away from the kitchen - something to do with the shared ventilation exhaust fan system. The irony is remarkable but the shame is on the builder  :Eek:  
When I installed one at home I vented it outside using flexible ducting as I had no choice given the raked ceiling and beam locations. Suffice to say if I ever do have a rangehood fire once the *plastic fan* has melted and burnt and the ducting is gone there will be nothing left to burn, so I'm comfortable with that. Using rigid ducting may help initially but if the fire takes hold, the fan will burn and if the grease build up in the flue is substantial, then the metal flue will radiate heat into the ceiling space and ignite anything flammable in there eg dust, blow in insulation, wiring etc. Eventually the ducting will fail, as they are not fire rated. Nothing is foolproof, so clean it periodically, and don't leave stuff on the stove unattended - simple solution. 
BTW bbq rangehoods have a different standard (due to "flareups" (laughable)) so prices start at $2500...........

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## PhilT2

> the metal flue will radiate heat into the ceiling space and ignite  anything flammable in there eg dust, blow in insulation, wiring etc.

  Aren't all types of insulation fire retardent?

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## Firey05

> Aren't all types of insulation fire retardent?

  Phil short answer is yes and no. Blow in insulation (brand names such as cool and cosy etc) is basically mulched up paper/cardboard and treated with a fire retardent. When first installed its all cool and cosy. Over time, however, the fire retardant breaks down and loses effectiveness. In WA we have had a spate of house fire caused by down lights (halogens) not installed with shrouds, heating the insulation to the point of smouldering, and consequently, ignition.  
I have it in my house and I am in the process of having it removed and replaced as the house is 20 years old now and no doubt the insulation would be classed as flammable by now.

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## PhilT2

Most of the fires I heard about were in homes that had just had the insulation done under the govt scheme. Under those circumstances the insulation would have been new and the fire retardant should have worked. Something funny going on there. 
Have you considered having your insulation tested to see if it is still fire retardant?

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## Firey05

> Most of the fires I heard about were in homes that had just had the insulation done under the govt scheme. Under those circumstances the insulation would have been new and the fire retardant should have worked. Something funny going on there. 
> Have you considered having your insulation tested to see if it is still fire retardant?

  We are on different wavelengths here Phil. I am talking specifically of blow in insulation which was very popular 10-20 years ago. The fires I am refering to are as a result of halogen downlights and are not connected with the fed gov insulation scheme.  
I have tested the insulation in my roof with a blow torch - it burns and shouldn't.

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## PhilT2

Sorry, didn't explain that well enough. The blow in type of insulation seems to nave been widely used during the govt rebate. However due to poor training etc some installers failed to fit covers to halogen downlights and as a result the downlights were buried in insulation. My understanding was that this had caused some of the recent fires.  
What worries me is that for this to happen some people must have been manufacturing this insulation material to an inferior standard. If so how many houses have this crap in their roofs and are these guys still in business? 
With regard to your insulation, I've checked some sites of manufacturers of this material to try and find out what its lifespan should be. Some overseas makers guarantee the product for the life of the building. I assumed this meant the fire rating as well.  
I checked the data sheet for the fire retardant (borax decahydrate) and can find nothing on its effective lifespan. Do you know if your insulation has lost its fire retardent ability over time or could it have never been up to spec originally? And with the blowtorch test, my understanding is that the flame is applied to the material for a min of 10 seconds and when the flame is removed the insulation must self extinguish within 15 seconds. Is that how you understand it? 
Not wanting to be a pain in the a*** but I am currently chasing a job with the inspection program and want to be sure I understand this correctly. Thanks.

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## barney118

Good thread, this is a job I need to finish off. Couldnt see an outcome in the tread regarding using a whirly bird to vent? Also the rangehood came with concertina ducting (feels like its PVC or something grey not the shiny stuff like foil you can get).
looks like I have 3 options:
1. Through the roof. (grease sliding down roof). Weather tight options? I installed my whirlies under the ridge cap so I wouldnt get any water ingress flowing to the high side.
2. Through the wall (grease sliding down wall and maybe under eave). Easiest $15 cover from bunnings.
3. Through the aspestos eave lining.(grease fll to floor) but need to cut through the yuckky stuff. $15 cover from bunnings 
I like option 3 for the grease option, do I need to get new ducting stuff? if so which one? Jago you mentioned fitted pipework. 
Looks like this has jumped to the top of my list, waiting for some help from you guys now.

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## Firey05

Phil 
I really have not idea who installed mine, whether it has any guarantee, wasn't up to spec initially or has lost its flame retardant ability over time. From the research I have done, I came to the conclusion (and therefore assumed) that it indeed lost flame retardant properties over the 21 years since installation. Apparently it is not uncommon for this to happen with some products installed back around 1990. 
No doubt there were many dodgy installers (recently) out there and some may have lead to combustion in the roof space. Personally and specific to WA, we have had roof space fires for various reasons, but they often have involved halogens, poor installation and blow in insulation. I think it would be fair to say these elements are overly represented in the stats. The fact of the matter is halogens fitted without shrouds in close proximity to anything increase the fire risk in the ceiling space. Even dust poses a risk in terms of a dust explosion (given the right conditions). 
The test I did on my insulation was not in controlled conditions but it didn't extinguish as quickly as you would expect (or would have liked). It smouldered for a fair time after the ignition source was removed. Quite honestly I don't know the standard test or the time required, but I would suggest it would have to be under controlled conditions (no wind, flame at a certain temperature etc), so my test was far from perfect. If my insulation were to pass the standard I still wouldn't be happy having it in my roof. 
Good luck with the job 
Cheers   

> Sorry, didn't explain that well enough. The blow in type of insulation seems to nave been widely used during the govt rebate. However due to poor training etc some installers failed to fit covers to halogen downlights and as a result the downlights were buried in insulation. My understanding was that this had caused some of the recent fires.  
> What worries me is that for this to happen some people must have been manufacturing this insulation material to an inferior standard. If so how many houses have this crap in their roofs and are these guys still in business? 
> With regard to your insulation, I've checked some sites of manufacturers of this material to try and find out what its lifespan should be. Some overseas makers guarantee the product for the life of the building. I assumed this meant the fire rating as well.  
> I checked the data sheet for the fire retardant (borax decahydrate) and can find nothing on its effective lifespan. Do you know if your insulation has lost its fire retardent ability over time or could it have never been up to spec originally? And with the blowtorch test, my understanding is that the flame is applied to the material for a min of 10 seconds and when the flame is removed the insulation must self extinguish within 15 seconds. Is that how you understand it? 
> Not wanting to be a pain in the a*** but I am currently chasing a job with the inspection program and want to be sure I understand this correctly. Thanks.

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## Bloss

> Phil short answer is yes and no. Blow in insulation (brand names such as cool and cosy etc) is basically mulched up paper/cardboard and treated with a fire retardent. When first installed its all cool and cosy. Over time, however, the fire retardant breaks down and loses effectiveness. I

  Well no actually - blow in _cellulose_ insulation is sometimes used, but in Oz rockwool is the most common blow-in loose fill followed by fibreglass. In any case fire retardation properties of borate treated cellulose does not 'break down' and become less fire resistant. Like all loose fill insulation it can settle over time - but that reduces its insulating capacity and has no impact on fire safety. http://en.wikipedia.org/wiki/Cellulose_insulation. But if your insulation is burning fair chance it was faulty from the beginning - installed by 'Dodgy Bros' no doubt - and a good idea to remove it. 
The fires that have been in roofs (BTW at a significantly reduced rate compared to historical roof space fires incidence during the supposedly dangerous federal insulation program!) have mostly been due to failure to comply with clearances around halogen light fittings (as has been mentioned). The insulation is not what catches fire - the insulation causes the heat build up as it traps the heat that is designed to escape into the air of the roof space, and the fitting itself gets too hot (it has plastic, paint & metal and even when running normally will be way too hot to touch) and smolders and/or burns causing the paper on the plasterboard to catch fire and/or timber members too. Coroners and other technical reports are available to confirm this.

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