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

The question on whether you can duct a range hood used for domestic cooking purposes into a ceiling cavity, roof space or have it recirculate back into the room continues to crop up and cause confusion. This information sheet explains what rules apply to kitchen exhausts in residential buildings.

What are the requirements for kitchen range hoods in houses?

To get to the point with minimal explanation; the answer is yes you can duct a range hood used for domestic cooking purposes into a ceiling cavity, roof space or have it recirculate back into the room if the manufacturer of the range hood advises that you can in their installation specifications.

There are no provisions in the Building Code of Australia (BCA) or its referenced Australian Standards to say that you can’t. The most relevant provision in this situation is in AS/NZS 3000 The Wiring Rules where it states that all installations of electrical equipment must be done in accordance with the manufacturer’s instructions.

For toilets, bathrooms and laundries, the BCA Volume Two identifies, in Clause 3.8.5.2 (c), when and where a range hood or an exhaust fan is required to be ducted to the outside or ventilated roof space; but kitchens are not included in this provision.

What about AS 1668.2?

Many people quote the Australian Standard 1668.2 – 2002 The use of ventilation and air-conditioning in buildings Part 2: Ventilation design for indoor air contaminant control (excluding requirements for the health aspects of tobacco smoke exposure) as an appropriate guideline to the installation of a range hood. More specifically people tend to quote Clause 5.10 Air Discharges 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 (of course there are always exceptions, hence why you need to read the whole document, but this is the general rule). The prescriptions in AS 1668.2 for kitchen exhaust hoods relate to commercial kitchens.

To see whether your project is required to have a mechanically ventilated exhaust system installed to the requirements of AS 1668.2, the quickest way is to refer to Figure 5.1 of the Standard which sets out a general guide of when the provisions are applicable.

Basically if the residential kitchen meets the following 2 parameters you do not need to comply with AS 1668.2.

1. The kitchen has natural ventilation as prescribed in the Building Code of Australia
   having openings (windows, doors etc.) with an aggregate size of at least 5% of the floor area of the room; and
2. The effluent being removed by the range hood is not classified as being Type A or Type B as defined by AS 1668.2, being:
   effluent created from domestic cooking and domestic cooking equipment is not classified as either of these Types

If you are building for client who intends to use their home kitchen for commercial purposes or if they are installing commercial kitchen equipment, then you may need to refer to AS 1668.2 to see whether more prescriptive requirements for the installation of a range hood are required.

Do you have to install a range hood in a kitchen?

Your client has the option of not installing a range hood at all. If they don’t want to or want to install the range hood at a later date, you must ensure that any combustible materials meet the necessary clearances requirements around the cooktop and suggest to the client that they incorporate space for the installation of the range hood at a later date.

So the main thing when installing a kitchen range hood in a domestic situation is to refer to the range hood manufacturer’s specifications and see what they advise.

For more information on these requirements, HIA members can contact the Building Services staff in your region.

_{DISCLAIMER – the above is intended to provide general information in summary form. The contents do not constitute specific advice and should not be relied upon as such. Formal specific advice should be sought by members with respect to particular matters before taking action.}