Selina Zwolsman discusses the ins and outs of exhausts in Australian homes.
Selecting a suitable rangehood for a new home or renovation can be challenging, but working out a ducting solution can be downright exhausting!
In this feature, the Kitchen and Bathroom Designers Institute of Australia Ltd (KBDi) explores the regulations around ducting, and raises the issue of best practice design.
Beginning with the basics: Recirculating v ducting
Recirculating rangehoods (also referred to as filtered or non-ducted) extract cooking fumes and pass them through filters before recirculating the air back into the room. While they’re not removing vapours entirely from the workspace, they are often the only option for the extraction of steam and smoke due to building restraints and/or lean budgets.
Clients who select a filtered option should be reminded of the requirement to change and clean filters regularly. The manufacturer’s recommendations and the type of cooking preferred by your client will both determine the frequency of replacement, and the ongoing costs should be considered for a long-term budget comparison.
Ducted rangehoods (or extractor rangehoods), on the other hand, extract the cooking fumes from the kitchen and expel them from the working space to another through a ducting system. The end destination of any discharged air is, of course, the main point for discussion: an easy-way-out (and DIY speciality) is to expel the fumes into the ceiling cavity. The resulting collection of humidity and grease can naturally present some genuine health issues and significant fire hazards.
The ultimate solution (best practice design) is to extend a fire-rated ducting system to the house exterior, ensuring air is released to an open atmosphere, but what are the legal requirements?
Complying with the code
The National Construction Code (NCC 2016 Volume Two) defines the general requirements for ventilation in residential housing. Clause 126.96.36.199 sets out the various means of ensuring adequate air quality is maintained in a building, referring pointedly to sanitary compartments, laundries and bathrooms, but not explicitly mentioning rangehood ducting or the ventilation of kitchens.
Further, with respect to ventilation, the NCC refers to the following performance requirement:
(a) A space within a building used by occupants must be provided with means of ventilation with outdoor air which will maintain adequate air quality.
(b) A mechanical air-handling system installed in a building must control—
(i) the circulation of objectionable odours; and
(ii) the accumulation of harmful contamination by micro-organisms, pathogens and toxins.
(c) Contaminated air must be disposed of in a manner which does not unduly create a nuisance or hazard to people in the building or other property.
Again, there is no reference to kitchens, rangehoods or ducting, but the reference to mechanical air handling should be noted.
NCC 2016 also makes reference to the following two Australian Standards.
AS1668 The use of ventilation and air conditioning in buildings
The NCC states that ‘except for an exhaust fan from a sanitary compartment, laundry or bathroom, Performance Requirement P2.4.5 is satisfied for a mechanical ventilation system if it is installed in accordance with AS 1668.2’. While this Standard does have a section relating to ‘Kitchen Exhaust Hood Systems’, it makes no reference to kitchens of a domestic nature. In its introductory ‘scope’, AS 1668.2 suggests that enclosures that may need mechanical ventilation include ‘spaces where high heat and vapour generation is likely [e.g. large commercial kitchens and laundries]’.
AS/NZS 5601.1:2013 Gas installations
AS/NZS 5601.1:2013 sets out the following guidelines with respect to rangehoods and gas appliances:
188.8.131.52 Domestic gas cooking appliances in combined living/sleeping areas
In a combined living/sleeping area, a domestic cooking appliance shall only be installed under a rangehood or exhaust fan which is ducted to outside.
Confused? Google the subject and you’ll see that many others are, too, and for this reason, KBDi has put together five fast key checkpoints to consider when selecting the right rangehood and method of extraction:
- Ask about the odour: ask your clients what kind of cooking they’re most likely to do, and get them to consider the volume of steam, smoke and greasy residue their favourite cooking styles will generate.
- Avoid voiding the warranty: if you’ve narrowed down your rangehood options, check the manufacturer’s installation instructions carefully. Determine what they require and make sure your clients don’t jeopardise their warranty.
- Investigate the possibilities for external extraction: obtain a quote from a licensed installer for an externally ducted system, and weigh up the costs with your clients.
- Ask the authorities: contact your state regulatory authority, and ask them how they interpret the NCC requirements in a domestic kitchen arrangement.
- Check with your Certifier: discuss the issue with your private certifier (if applicable) or local government authority, and see how they’re interpreting the ‘rules’.
Remember that good design practice should always be your decision driver: a well-designed kitchen will allow for the optimum air extraction with minimum health and safety implications.
Need a short and sweet summary of the above? KBDi’s Education Partner, Designer Training Australia, has prepared a Technical Bulletin outlining the rangehood regulations. This Bulletin (and a growing library of others) is available at no charge to all current Members of the KBDi. If you’re not a Member yet, find out more about this and other benefits of joining at kbdi.org.au.