Class 1a buildings are typically detached residential houses and also includes attached townhouses, row-houses and villas. A Class 1a dwelling can not be located above another dwelling or class of building.
The aim of improving energy efficiency in a building is to maximise thermal comfort of occupants whilst minimising the building’s energy consumption & running costs, thereby reducing greenhouse gas emissions.
Energy consumption in buildings is minimised by requiring buildings to contain the following features:
- Energy efficient building services, such as lighting, mechanical & hot water systems, and
- Treating the building envelope to reduce heat loss or gain in buildings or parts of buildings that are provided with air-conditioning or are likely to be provided with air-conditioning. Such areas are referred to by the BCA as conditioned space.
Building requirements
To achieve these objectives the building envelope must be constructed so as to satisfy the requirements of
- Part 3.12 of the Building Code of Australia Housing Provisions (BCA)
- AS/NZS 4859.1 – Materials for the thermal insulation of buildings
- Manufacturer’s Specification to ensure that the product performs as tested.
State Variations
In developing the design of your building, it is important to note that there are also significant state variations that alter, limit or increase the level of compliance required with the national energy efficiency provisions. The following states contain variations to the national provisions for energy efficiency:
- NSW – Part 3.12, for class 1 and 10 buildings subject to BASIX, the BCA energy efficiency provisions of BCA 2009 as varied by the NSW Appendix are applicable. Reference to BCA 2009 will be required to meet these provisions
- Northern Territory – Part 3.12 of BCA 2010 is replaced with BCA 2009 Part 3.12
- Tasmania – Part 3.12 of BCA 2010 is replaced with BCA 2009 Part 3.12
- Victoria – Part 3.12 of BCA 2010 is replaced with BCA 2009 Part 3.12
- Western Australia – Part 3.12 of BCA 2010 is replaced with BCA 2009 Part 3.12
Alternative Solutions
If any of the above building requirements cannot be met either because of innovative development or there is a particular construction issue, the building would not comply the Deemed-to Satisfy Requirements of the Building Code of Australia and consequently a Construction Certificate or an Occupation Certificate will not be able to be issued.
To overcome this situation the an Alternative Solution may be able to be prepared in accordance with Clause 1.0.8, 1.0.9, & 1.0.10 of the BCA, demonstrating that the method of construction will satisfy Performance Requirements P2.6.1 and P2.62.2:
- Providing evidence that the form of construction satisfies the BCA;
- Using a Verification Method as set out in the BCA such as V2.6.2.1 or V2.6.2.2
- Comparison with the Deemed-to-Satisfy provisions
- Expert judgement.
General Deemed-to-satisfy Requirements Insulation
To satisfy the Deemed-to-Satisfy provisions of the BCA with respect to insulation, the first step is to refer to the Figure 1.1.4 of the BCA which establishes the climatic zone for the proposed building.
- Based on the climatic zone, Clause 3.12.1.2 and Table 3.12.1.1 of the BCA Housing Provisions sets out the minimum Total R-Value that needs to be achieved for the roof of that particular Class 1 building in the particular location.
- Clause 3.12.1.4 and Table 3.12.1.3 of the BCA provides additional requirements for calculating the minimum Total R-Values the external wall of a Class 1 building.
- Clause 3.12.1.5 & Table 3.12.1.4 provides additional requirements for calculating the minimum Total R-Values for floors.
The R-value is a measure of the insulation systems effectiveness, which must be determined in accordance with Part 4 of AS/NZS 4859.1, namely by testing; calculation and this information must be provided in the labelling by the manufacturer. Therefore when purchasing insulation it is critical that the product has been labelled in accordance with Clause 3.1 of AS/NZS 4859.1.
Insulation is only one element of construction when determining Total R-Values. The ‘Figures’ contained within Part 3.12.1 contain Total R-Values for some typical, roof, ceiling, wall and floor construction methods, upwards as well as downwards, that is insulation must prevent the flow of heat from the warm side to the cold side of the element.
Clause 3.12.1.1 of the BCA Housing Provisions provides basic construction details that will need to be adhered to, such as:
- Insulation must abut or overlap adjoining insulation;
- Forms a continuous barrier with ceilings, walls and floors;
- Does not adversely affect domestic services or fittings (for instance, electrical wiring may overheat etc)
- Reflective insulation is provided with requires airspace, is fitted close to openings (such as windows and doors) and is provided with adequate support;
- Bulk Insulation must maintain its position, thickness and to ensure that ceiling insulation overlaps uninsulated walls
Note: See also Class 10a requirements if your building involves an attached garage or similar.
DTS Requirement for Insulating Roof
The space under a roof or ceiling in a Class 1 building must achieve the Total R-Value specified in Table 3.12.1.1. Consideration must also be given as to whether insulation is to be used to prevent heat coming into the building (i.e. downwards such as in summer) or heat escaping from the building (i.e. upwards such as in winter).
Where a metal roof is fixed to metal purlins there must be a thermal break of at least R 0.2 between the metal roof and it’s supporting member. Typical roof & ceiling construction values are listed in Figure 3.12.1.1.
In climate zones 1, 2, 3, 4 and 5, the Total R-Value specified in Table 3.13.1.1a is reduced by 0.5 where the required insulation is laid on the ceiling and the roof space is ventilated by:
- Gable vents, ridge vents, eave vents, roof vents or the like that:
- Are evenly distributed to allow an unobstructed flow of air; and
- Are located to ensure, where practicable, there are no dead airspaces; and
- Have an aggregate fixed open area of not less than 1.0% of the ceiling area; or
- Not less than 2 wind-driven roof ventilators having an aggregate opening area of not less than 0.14m2 in conjunction with gable vents, ridge vents, eave vents, roof vents or the like having an aggregate fixed open area of not less than 0.2% of the ceiling area.
Further explanatory information regarding roof construction is contained within the pink shaded background areas of Clause 3.12.1.2 of the BCA Housing Provisions.
DTS Requirement for Insulating Walls
Each part of an external wall must satisfy the requirements of Table 3.12.1.3a for all walls or table 3.12.1.3b for walls with a surface density of not less than 220kg/m3, except for:
- Opaque non-glazed openings such as doors, garage doors, vents, penetrations, shutters and the like; and
- Glazing unless covered in Table 3.12.1.3b
It should be noted that wall linings fixed to metal framing must be separated from the metal framing by a thermal break having an R-Value not less than R0.2
Typical wall construction values are listed in Figure 3.12.1.3. Also, further explanatory information regarding wall construction is contained within the pink shaded background areas of Clause 3.12.1.3 of the BCA Housing Provisions.
DTS Requirement for Insulating Floors
A suspended floor must achieve the Total R-Values in Clause 3.12.1.5 and Table 3.12.1.4 for heat flow in a downwards direction. Floors with unenclosed sub-floor areas generally required higher Total R-Values than enclosed sub-floor areas.
The requirements of Table 3.12.1.4 do not apply to an intermediate floor in a building with more than one story.
Suspended slabs with in-slab heating or cooling must be provided with insulation around the vertical edge of its perimeter and underneath the slab with an insulation having an R-Value of not less than R2.0 which may include insulation installed to meet the requirements of; and that is enclosed beneath, must have a barrier to prevent convection installed below floor level between the airspace under the floor and any wall cavities.
Concrete slabs-on-ground with in-slab heating or cooling
- must have insulation with an R-Value of not less than R1.0, installed around the vertical edge of its perimeter; and
- when in Climate Zone 8, must have insulation with an R-Value of not less than R2.0 installed under the slab.
Insulation required must be:
- water resistant
- continuous from the adjacent finished ground level to a depth of not less than 300mm or at least the full depth of the vertical edge of the concrete slab-on-ground (Refer figure 3.12.1.4)
Typical floor construction values are listed in Figure 3.12.1.5. Also, further explanatory information regarding floor construction is contained within the pink shaded background areas of Clause 3.12.1.5 of the BCA Housing Provisions.
DTS Requirement for Building Sealing
To maintain comfortable conditions consideration must also be given to heat loss or gain via openings in buildings. The requirements are contained in Clause 3.12.3 of the BCA Housing Provisions.
Building sealing applies to Class 1 buildings and Class 10a buildings with a conditioned space, except:
- In climate zone 1, 2, 3 & 5 where the only means of air-conditioning is an evaporative cooler;
- For ventilating a gas appliance;
- A Class 10a building used for accommodation of vehicles
Furthermore construction joints such as between wall and floor (or wall and ceiling) are to be tight fitting or sealed using caulking or joinery items such as architraves, skirtings and cornices.
Exhaust fans are to be fitted with a self-closing damper or the like when serving a conditioned space or habitable room in a Climatic Zone 4, 6, 7, 8.
Roof lights serving a conditioned space or habitable room in climate zones 4, 6, 7 & 8 must be sealed such as by weatherproof seals if it is a roof window, or a ceiling diffuser, or operable shutter system.
Further explanatory information regarding building sealing is contained within the pink shaded background areas of Part 3.12.3 of the BCA Housing Provisions.
DTS Requirement for Air movement
To maintain occupant comfort air movement is required to be provided in accordance with Part 3.12.4 of the BCA Housing Provisions.
The aim of Part 3.12.4 is to ensure improve occupant comfort by providing evaporative coolers or ceiling fans. The requirements only relate to habitable rooms in Class 1 buildings.
Clause 3.12.4.1 and Table 3.12.4.1 of the BCA Housing Provisions should be referred to for more detail.
DTS Requirement for Services
A Class 1 building must be provided with services that facilitate efficient energy use.
Central heating water piping must be thermally insulated whenever it is not within a conditioned space to achieve the minimum R-values of Table 3.12.5.1 of the BCA Housing Provisions and must also be:
- Be protected against the effects of weather and sun
- Be able to withstand the temperatures of the piping or ductwork
BCA Clause 3.12.5.3 details the requirements for sealing and insulating of supply and return ductwork used in a system that heats or cools a building.
Such ductwork must be thermally insulated with insulation complying with AS/NZS 4859.1 and sealed against air loss in accordance with AS4254, or with a sealant and draw band for flexible ductwork. The ductwork achieves a Total R-value specified in Table 3.12.5.2 when outside the insulated building envelope.
Table 3.12.5.2 Heating and Cooling Ductwork and Fittings - minimum material R-Value
| Ductwork element |
Minimum material R-Value for ductwork and fittings in each climate zone |
| Heating-only system or cooling-only system including an evaporative cooling system |
Combined heating and refrigerated cooling system |
| 1, 2, 3, 4, 5, 6 and 7 |
8 |
1, 3, 4, 6 and 7 |
2 and 5 |
8 |
| Ductwork |
1.0 |
1.5 |
1.5 (see note) |
1.0 |
1.5 |
| Fittings |
0.4 |
Note:
The minimum material R-Value required for ductwork may be reduced by 0.5 for combined heating and refrigerated cooling systems in climate zones 1, 3, 4, 6 and 7 if the ducts are:
- under a suspended floor with an enclosed perimeter; or
- in a roof space that has insulation of not less than R0.5 directly beneath the roofing.
Explanatory information:
- For information on an enclosed perimeter, refer to the explanatory information following Table 3.12.1.4.
- Insulation for refrigerated cooling ductwork should have a vapour barrier to prevent possible damage by condensation.
- The insulation levels in the following table are typical examples of materials that can be used to insulate ductwork and fittings and the R-Values they contribute. Other methods are available for meeting the Total R-Values required by Table 3.12.5.2.
Further explanatory information regarding building sealing is contained within the pink shaded background areas of Part 3.12.3 of the BCA Housing Provisions.
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Definitions
Conditioned space means a space within a building that is heated or cooled by the buildings domestic services, excluding a non-habitable room in which a heater with a capacity of not more than 1.2kW is installed.
Domestic Services means the basic engineering systems of a house that use energy or control the use of energy; and:
(a) Includes heating, air-conditioning, mechanical ventilation and hot water systems
(b) Excludes cooking facilities and portable appliances
Envelope for the purposes of Part 2.6 and 3.12 means the parts of the building’s fabric that separates artificially heated or cooled spaces from-
• The exterior of the building; or
• Other spaces that are not artificially heated or cooled
Fabric – for the purposes of part 2.6 and 3.12 means the basic building structural elements and components for the building including the roof, ceilings walls and floors.
Habitable room means a room used for normal domestic activities, and—
(a) includes a bedroom, living room, lounge room, music room, television room, kitchen, dining room, sewing room, study, playroom, family room and sunroom; but
(b) excludes a bathroom, laundry, water closet, pantry, walk-in wardrobe, corridor, hallway, lobby, photographic darkroom, clothes-drying room, and other spaces of a specialised nature occupied neither frequently nor for extended periods
Piping means an assembly of pipes, with or without valves or other fittings, connected together for the conveyance of liquids.
R-Value means the thermal resistance (m2.K/W) of a component calculated by dividing its thickness by its thermal conductivity
Reflective Insulation means a building membrane with a reflective surface such as a reflective foil laminate, reflective barrier, foil batt or the like capable of reducing radiant heat flow.
Solar Heat Gain Co-efficient (SHGC) means the fraction of incident irradiance on glazing or a roof light that adds to the heat of a buildings space.
Total R-Value – means the sum of the R-values of the individual component layers in a composite element including any building material, insulation material, airspace and associated surface resistances.
Ventilation Opening means an opening in the external wall, floor or roof of a building designed to allow for air movement into or out of the building by natural means including a permanent opening, an openable part of a window, a door or other device which can be held open.
Verification Method means a test, inspection, calculation or other method that determines whether a Building Solution complies with the relevant Performance Requirements