Part F4 Light and ventilation (DtS)
F4.0 Deemed-to-Satisfy Provisions
Where a solution is proposed to comply with the Deemed-to-Satisfy Provisions, F4.0 clarifies that compliance with F4.1–F4.12, and Parts G6 andH3, if applicable, will achieve compliance with FP4.1 - FP4.5.
F4.1 Provision of natural light
Natural light must be provided in:
Class 2 buildings and Class 4 parts of buildings — to all habitable rooms.
Class 3 buildings — to all bedrooms and dormitories.
Class 9a and 9c buildings — to all rooms used for sleeping purposes.
To specify the rooms in Classes of buildings where natural light is required.
The provision of natural light is substantially a health and amenity issue. It is considered of particular importance in all “living” and “sleeping” areas in residential buildings occupied by people for an extended period of time. The BCA consistently assumes that this is the case with Class 2 buildings and Class 4 parts, but not with Class 3 buildings.
Occupants of Class 3 and Class 9a buildings do not reside in the same building for an extended period of time. F4.1 extends this assumption to the “living” areas (shared and unshared) of such buildings. For this reason, the BCA only requires the provision of natural light to sleeping areas in Class 3 and Class 9a buildings.
F4.1(b) assumes that in Class 3 buildings the occupants spend more time in their “sleeping” accommodation than they do in “living” areas. This is usually the case in Class 2 buildings and Class 4 parts.
F4.1(c), with regard to Class 9a and 9c buildings, takes account of the fact that occupants will generally be in their beds throughout the day and natural light will be important to them.
It is considered desirable that school and pre-school children are able to view the outside environment, and work or play using natural light. Accordingly, buildings such as kindergartens and schools must provide natural light to playrooms and classrooms.
F4.2 Methods and extent of natural light
Required natural light must be provided by—
have an aggregate light transmitting area measured exclusive of framing members, glazing bars or other obstructions of not less than 10% of the floor area of the room; and
are open to the sky or face a court or other space open to the sky or an open verandah, carport or the like; or
Except in a Class 9c aged care building, in a Class 2, 3 or 9 building or Class 4 part of a building a required window that faces a boundary of an adjoining allotment or a wall of the same building or another building on the allotment must not be less than a horizontal distance from that boundary or wall that is the greater of—
generally — 1 m; and
in a patient care area or other room used for sleeping purposes in a Class 9a building — 3 m; and
50% of the square root of the exterior height of the wall in which the window is located, measured in metres from its sill.
where the window faces an adjoining allotment, another building or another wall of the same building, it must not be less than a horizontal distance of 3 m from the adjoining allotment, other building or wall.
To specify the requirements for the size and location of windows, including roof lights to provide required natural light.
A window includes roof lights, glassed louvres and glazed doors (see definition in Schedule 3).
A roof light generally receives greater exposure to sunlight than a window because of its orientation to the sky and consequently, the size of a roof light as a percentage of the floor area served is permitted to be smaller than for a window serving the same floor area.
To achieve the requirements for natural light when both windows and roof lights are provided, a proportional combination of F4.2(a)(i) and (ii) can be used through F4.2(a)(iii). This is explained in the following example.
Method for determining proportional combination of windows and roof lights.
Description of above diagram
Area of the room which requires natural light is 100 m2.
No natural light borrowed from adjoining rooms.
Required windows to provide natural light must have a light transmitting area of at least 10% of the floor area.
10% of 100 m 2 = 10 m 2
Or, roof lights to provide natural light must have a light transmitting area of at least 3% of the floor area.
3% of 100 m 2 = 3 m 2
In the formula below, 3% of the floor area is expressed as the fraction 0.03 and 10% of the floor area is expressed as the fraction 0.1.
Formula—for the area of window(s) required to compensate for roof light shortfall
Area of room covered by the roof light = (Area of roof light) / 0.03
Required window(s) area = [(Floor area) – (Area covered by the roof light)] / 10
Area of windows required to compensate for roof light shortfall
If the roof light = 1 m2
Area of room covered by the roof light = (1 m2 / 0.03) = 33.33 m2
Required window(s) area = (100 m2 – 33.33 m2) / 10 = 6.67 m2
Formula—for the area of roof lights required to compensate for window(s) shortfall
Area of room covered by the window(s) = (Area of window(s)) / 0.1
Required roof light area = [(Floor area) – (Area covered by the window)] / 33.33
Area of roof lights required to compensate for window shortfall
If the window = 5 m2
Area of room covered by the window(s) = (5 m2 / 0.1 m2) = 50 m2
Required roof lights area = (100 m2 – 50 m2) / 33.33 m2 = 1.5 m2
- For the purpose of this example a window excludes a roof light.
- The same proportional calculation principle applies if—
- two or more windows are used; or
- two or more roof lights are used.
All windows, both required and non-required, must comply with the various requirements of the BCA’s fire-safety provisions, such as C3.2 for openings in external walls, and Clause 3.6 of Specification C1.1 for roof lights.
F4.2(b) does not prohibit windows closer to the boundary than one metre (or three metres in the case of a patient-care area in a Class 9a building). However, if a window is located within these distances, F4.2(b) does not allow it to be considered as providing required natural light to the subject room.
Figure F4.2(1) illustrates the method of measuring the distance of the window from:
- an adjoining allotment boundary;
- a wall of the same building; and
- a wall of another building on the same allotment.
F4.2(c) contains requirements for Class 9c buildings. The requirement for the window sill to be not more than 1 m above floor level and at least 3 m from an adjoining allotment, another building or wall is to maintain amenity for residents who spend a significant amount of time sitting on chairs or lying in bed. Figure F4.2(2) illustrates the method of measuring these distances.
F4.2(d) contains requirements for Class 9b early childhood centres. The well-being of children in these types of buildings is enhanced through improved interaction with the outdoor environment by the provision of 50% of window sills in children's rooms required to be located not more than 500 mm above the floor level.
The following is not considered a children's room:
- a passageway or thoroughfare (including door swings);
- a toilet and hygiene facilities;
- a room permanently set aside for storage;
- a room for staff or administration;
- a kitchen, unless the use of the kitchen is part of an educational program provided by the service; or
- any other space that is not suitable for children.
F4.3 Natural light borrowed from adjoining room
Natural light to a room in a Class 2 building or Class 4 part of a building or in a sole-occupancy unit of a Class 3 building, may come through one or more glazed panels or openings from an adjoining room (including an enclosed verandah) if—
both rooms are within the same sole-occupancy unit or the enclosed verandah is on common property; and
the glazed panels or openings have an aggregate light transmitting area of not less than 10% of the floor area of the room to which it provides light; and
the adjoining room has—
To allow natural light to be “borrowed” from an adjoining room.
F4.3 applies only to a room in:
- a Class 2 building;
- a Class 4 part; or
- a sole-occupancy unit in a Class 3 building.
For these Classes, it is sometimes acceptable for a room’s required natural light to be “borrowed” from an adjoining room (i.e. an adjoining room’s light can be used to help make up the total amount of natural light required in the subject room).
The use of borrowed light is acceptable if the provisions of F4.3 are applied to the subject room and to the total area of each relevant room.
Any borrowed natural light must be from an adjoining room over which occupants of the subject room have some control. F4.3(a)(i) therefore requires that the adjoining room be within the same sole-occupancy unit or be an enclosed verandah on common property. As a consequence, the required natural light cannot be from another sole-occupancy unit.
Direct natural light provided from another source is intended to mean light from a window or roof light in the subject room. As the provision relates to natural light obtained from an adjoining room, 'another source' refers to direct natural light provided to the subject room which does not meet the required allowance of either 3% or 10% of the floor area for roof lights and windows respectively. By not meeting the required amount of natural light, the 'direct natural light from another source' can be used as a supplement to the natural light required from an adjoining room.
To borrow natural light from another room, F4.3(a)(ii) allows light to pass through glazed panels or openings from an adjoining room which, under F4.3(a)(iii), must have windows, roof lights or a combination of windows and roof lights of a minimum size in proportion to the combined floor areas of both rooms. The minimum size of the glazed panels or openings, and the minimum size of the windows to the adjoining room, are illustrated in Figure F4.3.
If a doorway is used as an opening to obtain light from an adjoining room, any door is required to transmit natural light directly from outside a building to the room concerned when in the closed position (see Figure F4.3).
The area of openings needed to transmit natural light from an adjoining room may be reduced proportionally to the size of any openings in the subject room which transmit natural light directly from the outside.
The same principle for Opening A in Figure F4.3 can be applied for roof lights by substituting the required 10% opening in respect to the combined floor area with 3% of the combined floor area. It is also permitted to use a proportional combination of windows and roof lights. See the example in the comments on F4.2 for an explanation.
F4.4 Artificial lighting
Artificial lighting must be provided—
in required stairways, passageways, and ramps; and
if natural light of a standard equivalent to that required by F4.2 is not available, and the periods of occupation or use of the room or space will create undue hazard to occupants seeking egress in an emergency, in—
Class 4 parts of a building — to sanitary compartments, bathrooms, shower rooms, airlocks and laundries; and
Class 2 buildings — to sanitary compartments, bathrooms, shower rooms, airlocks, laundries, common stairways and other spaces used in common by the occupants of the building; and
The artificial lighting system must comply with AS/NZS 1680.0.
The system may provide a lesser level of illumination to the following spaces during times when the level of lighting would be inappropriate for the use:
A museum, gallery or the like, where sensitive displays require low lighting levels.
A discotheque, nightclub or the like, where to create an ambience and character for the space, low lighting levels are used.
To specify the location and other requirements for required artificial lighting.
Artificial lighting is required where it is necessary to minimise any hazard to occupants during an emergency evacuation.
F4.4(a)(i) sets out those places where artificial lighting is always required. However, it does not require such lighting to be illuminated at all times.
F4.4(a)(ii) sets out those places where artificial lighting is required if the standard of natural light required by F4.2 is unavailable, and the periods of occupation of the areas, or the use of the space, will create an undue hazard during an evacuation.
Determination of whether or not the periods of occupation of the specified areas will create an undue hazard during an evacuation is a judgement, which requires a “performance-type” assessment.
Class 4 parts of buildings are subject to F4.4(a)(ii) only with regard to wet areas and airlocks. (Any required stairways and the like in the rest of the building, which contains the Class 4 part, are required to be artificially lit under F4.4(a)(i)).
Class 2 buildings are subject to F4.4(a)(ii) with regard to wet areas, airlocks and any common areas such as stairways, etc used in common by occupants.
Class 3 and Class 5–9 buildings are subject to F4.4(a)(ii) with regard to all rooms frequently occupied, and all corridors, stairways and similar circulation routes and paths of egress. Unless they are “frequently occupied”, wet areas (including those in Class 3 buildings) are not subject to F4.4(a)(ii).
Apart from the “performance-type” judgement regarding the location of artificial lighting in those areas specified in F4.4(a)(ii), the remainder of the requirements are contained in the AS/NZS 1680.0 specified in F4.4(b).
F4.4(c) gives a concession for compliance with F4.4(a) in specific buildings which have lower levels of lighting as part of their normal operation. For example, the lighting levels specified in AS/NZS 1680.0 would be inappropriate during the screening of a movie in a cinema or may lead to damage of artworks in a gallery.
F4.5 Ventilation of rooms
natural ventilation complying with F4.6; or
To state the natural and mechanical ventilation requirements for rooms and buildings.
The specified rooms and buildings, and any other room occupied by a person for any purpose, must be provided with either:
- natural ventilation complying with F4.6; or
- mechanical ventilation or an air-conditioning system that complies with both of the Standards referenced in F4.5(b).
If a room or building is served by a mechanical ventilation or air-conditioning system for heating or cooling purposes and the system does not provide ventilation in accordance with AS 1668.2, then the room or building must also be provided with natural ventilation complying with F4.6. Natural ventilation would therefore need to be provided to rooms served by a typical domestic type wall mounted air-conditioning split system. In addition, F4.5 does not preclude natural ventilation serving a room or building if it is also served by a mechanical ventilation or air-conditioning system compliant with AS 1668.2.
F4.6 Natural ventilation
a suitably sized court, or space open to the sky; or
an open verandah, carport, or the like; or
an adjoining room in accordance with F4.7.
To specify the requirements for the size and location of windows providing required natural ventilation.
F4.6 requires that permanent openings, windows, doors or other openable means provide natural ventilation. It also deals with the size of such openings, and the locations to which such openings must open.
F4.6 does not require any of the required natural ventilation to be “fixed ventilation” or “permanent openings” as against “devices which can be opened”. The building proponent can make the decision.
If the natural ventilation openings are used only for ventilation purposes, roller shutters and doors can cover the openings if they achieve the performance standard in F4.6(a). However, if the openings are also used for egress purposes, they must comply with the requirements of provisions such as D2.19 and D2.21.
Under F4.6(b), the option of using prescribed natural ventilation opening sizes for Class 8 electricity network substations is removed. The prescribed ventilation openings are not conducive to Class 8 electricity network substations as they may allow excessive dust, humidity and other weather conditions that are detrimental to the sensitive and hazardous equipment used in these buildings.
F4.7 Ventilation borrowed from adjoining room
Natural ventilation to a room may come through a window, opening, door or other device from an adjoining room (including an enclosed verandah) if both rooms are within the same sole-occupancy unit or the enclosed verandah is common property, and—
in a Class 2 building, a sole-occupancy unit of a Class 3 building or Class 4 part of a building—
the room to be ventilated is not a sanitary compartment; and
in a Class 5, 6, 7, 8 (except a Class 8 electricity network substation) or 9 building—
To allow natural ventilation to be “borrowed” from adjoining rooms.
F4.7(a) applies only to:
- Class 2 buildings;
- Class 4 parts; and
- sole-occupancy units in Class 3 buildings.
Except for Class 8 electricity network substations, F4.7(b) applies only to Class 5–9 buildings.
It is sometimes acceptable for a room’s required natural ventilation to be “borrowed” from an adjoining room (i.e. an adjoining room’s ventilation can be used to help make up the total amount of ventilation required).
The use of borrowed ventilation is acceptable if the provisions of F4.7 are applied to the subject room and to the total area of each relevant room.
Any borrowed natural ventilation to a room must be from a room over which the occupants have some control. F4.7(a) therefore requires that the adjoining room be:
- within the same sole-occupancy unit; or
- an enclosed verandah on common property.
In a Class 2 or Class 3 building or Class 4 part, this requirement means that the natural ventilation cannot be from another sole-occupancy unit.
F4.7(a) and (b) allows a window, an opening, a door, or the like, to be used to “borrow” ventilation air from an adjoining room. The minimum area required for ventilation in residential buildings is illustrated in Figure F4.7.
In Class 5–9 buildings, the area of ventilation opening required under F4.7(b) is similar to that required for residential buildings, except that:
- the area of ventilation opening must be increased from 5% to 10%; and
- any part of the ventilation opening between the rooms more than 3.6 metres above the floor must not be included as part of the required ventilation area.
Under F4.7(c), the area of openings needed to transfer natural ventilation borrowed from an adjoining room may be reduced proportionally to the size of any window or other opening in the room which receives natural ventilation directly from the outside.
F4.8 Restriction on location of sanitary compartments
Sanitary compartments must not open directly into—
a kitchen or pantry; or
a public dining room or restaurant; or
a dormitory in a Class 3 building; or
a workplace normally occupied by more than one person.
To minimise the impact of unpleasant smells.
- airlocks or airlock equivalents; or
- mechanical exhaust ventilation and, in some cases, screening.
The odours from toilets can be unpleasant and so it is desirable to minimise their impact on adjacent areas such as:
- a kitchen or pantry;
- public-eating areas, but not domestic-eating areas (other than kitchens);
- Class 3 building dormitories (but no other sleeping areas);
- some assembly buildings (but not kindergartens, primary schools or open spectator stands); and
- most workplaces.
The exclusions include sleeping areas other than Class 3 dormitories. In houses, flats, motels and hotels the odours are usually generated by the resident/s, whereas, in a dormitory there is a high likelihood that:
- the odours are generated by unrelated people;
- the toilet-use ratio is higher; and
- there could also be a privacy issue.
Some other exclusions include kindergartens because staff need to keep children under continuous observation and open spectator stands because these are generally open to the air and therefore inherently well ventilated.
the sanitary compartment must be provided with mechanical exhaust ventilation and the doorway to the room adequately screened from view.
To specify requirements for airlocks or mechanical ventilation where toilets open directly into other rooms.
- airlocks or airlock equivalents; or
- mechanical exhaust ventilation and, in some cases, screening.
It is desirable to minimise toilet odours in particular areas. See F4.8 and F4.9 for airlock and mechanical exhaust ventilation where a builder wishes to locate a toilet close to, or open directly into, the areas specified in F4.8.
F4.10 * * * * *
a system of mechanical ventilation complying with AS 1668.2; or
a system of natural ventilation complying with Section 4 of AS 1668.4.
To specify ventilation requirements for carparks, to ensure car fumes are adequately removed.
F4.11 does not apply to an open-deck carpark because such carparks are provided with adequate, permanent, natural ventilation.
AS 1668.2 contains mechanical ventilation requirements for the Deemed-to-Satisfy Provisions.
F4.12 Kitchen local exhaust ventilation
A commercial kitchen must be provided with a kitchen exhaust hood complying with AS 1668.1 and AS 1668.2 where—
any cooking apparatus has—
a total maximum electrical power input exceeding 8 kW; or
a total gas power input exceeding 29 MJ/h; or
the total maximum power input to more than one apparatus exceeds—
0.5 kW electrical power; or
1.8 MJ/hour gas, per m2 of floor area of the room or enclosure.
To minimise the spread of cooking odours and fire from commercial kitchens.
The aim of F4.12 is to:
- reduce the prevalence of airborne fats, etc building up, and causing health and fire problems;
- reduce steam and smoke from cooking processes; and
- maintain the flow of air to reduce potentially obnoxious odours.
The figures in F4.12(a) relate to the size of any electrical or gas cooking apparatus, which may cause these problems.
The figures in F4.12(b) relate to the ratio of electrical or gas cooking apparatuses to room size, which may cause these problems.
The Deemed-to-Satisfy Provisions require exhaust hoods to comply with both AS 1668.1 and AS 1668.2.