NCC 2019 Volume Two
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Part 3.12.1 Building fabric
3.12.1 Application
(a)
The provisions of 3.12.1.1 to 3.12.1.5 apply to—
(i)
a Class 1 building; and
(ii)
a Class 10a building with a conditioned space.
(b)
The provisions of 3.12.1.6 apply to a Class 1 building with an attached Class 10a building.
3.12.1.1 Building fabric thermal insulation
(a)
Where required, insulation must comply with AS/NZS 4859.1 and be installed so that it—
(i)
abuts or overlaps adjoining insulation other than at supporting members such as columns, studs, noggings, joists, furring channels and the like where the insulation must butt against the member; and
(ii)
forms a continuous barrier with ceilings, walls, bulkheads, floors or the like that inherently contribute to the thermal barrier; and
Explanatory information:
Explanatory information:
- For example, in a two storey house with the second storey set back, the insulation in the first storey wall, the second storey wall and the roof over the set-back must be continuous. Therefore if the roof over the set-back has insulation on a horizontal ceiling, then insulation is also needed on the vertical in any ceiling space in order to connect the ceiling insulation to the second storey wall.
- To form a continuous barrier, insulation should be placed in gaps between window and door jambs, heads and sills, and the adjoining wall framing unless a gap is otherwise required. This may need to be compressible to allow for movement between members.
(iii)
does not affect the safe or effective operation of a domestic service or fitting.
Explanatory information:
Explanatory information:
Care should be taken when installing insulation to ensure that it does not interfere with the safety or performance of domestic services and fittings such as heating flues, recessed light fittings, light transformers, gas appliances and general plumbing and electrical components. This includes providing appropriate clearance as detailed in relevant legislation and referenced standards such as for electrical, gas and fuel oil installations.
(b)
Where required, reflective insulation must be installed with—
(i)
the necessary airspace, to achieve the required R-Value between a reflective side of the reflective insulation and a building lining or cladding; and
Explanatory information:
Explanatory information:
Airspace adjoining reflective insulation
For reflective insulation and the adjoining airspace to achieve its tested R-Value, the airspace needs to be a certain width. This width varies depending on the particular type of reflective insulation and the R-Value to be achieved.
(ii)
the reflective insulation closely fitted against any penetration, door or window opening; and
(iii)
the reflective insulation adequately supported by framing members; and
(iv)
each adjoining sheet of roll membrane being—
(A)
overlapped greater than or equal to 150 mm; or
(B)
taped together.
Explanatory information:
Explanatory information:
Adjoining sheets of roll membrane
Where reflective insulation also acts as a vapour barrier or sarking, both the minimum overlap and taping may be necessary.
(c)
Where required, bulk insulation must be installed so that—
(i)
it maintains its position and thickness, other than where it crosses roof battens, water pipes, electrical cabling or the like; and
Explanatory information:
Explanatory information:
Compression of bulk insulation
The R-Value of bulk insulation is reduced if it is compressed. The allocated space for bulk insulation must therefore allow the insulation to be installed so that it maintains its correct thickness when using the product’s stated R-Value, otherwise the R-Value needs to be reduced to account for any compression. This is particularly relevant to wall and cathedral ceiling framing whose members can only accommodate a limited thickness of insulation. In some instances, larger framing members or thinner insulation material, such as polystyrene boards, may be necessary to ensure that the insulation achieves its required R-Value.
(ii)
in a ceiling, where there is no bulk insulation or reflective insulation in the external wall beneath,it overlaps the external wall by greater than or equal to 50 mm.
Explanatory information:
Explanatory information:
- The R-Value of reflective insulation and its adjoining airspace is affected by the width of the airspace between a reflective side of the reflective insulation and the building lining or cladding. For further information on reflective insulation, refer to the explanatory information accompanying Figure 3.12.1.1.
- Artificial cooling of buildings in some climates can cause condensation to form inside the layers of the building envelope . Such condensation can cause significant structural or cosmetic damage to the envelope before it is detected. Associated mould growth may also create health risks to the occupants. Effective control of condensation is a complex issue. In some locations a fully sealed vapour barrier may need to be installed on the more humid, or generally warmer, side of the insulation. Note that Part 3.8.7 contains specific provisions for condensation.
3.12.1.2 Roofs
(a)
Subject to (b) and (e), a roof must—
(i)
achieve the Total R-Value specified in Tables 3.12.1.1a to 3.12.1.1g as appropriate, for the direction of heat flow; and
(ii)
where a pitched roof has a flat ceiling, have greater than or equal to 50% of the added insulation laid on the ceiling.
(b)
In climate zones 1, 2, 3, 4 and 5 the Total R-Value specified in Tables 3.12.1.1a to 3.12.1.1g as appropriate, is reduced by 0.5 where—
(i)
the required insulation is laid on the ceiling; and
(ii)
the roof space is ventilated by—
(A)
gable vents, ridge vents, eave vents, roof vents or the like that—
(aa)
are evenly distributed to allow an unobstructed flow of air; and
(bb)
are located to ensure, where practicable, there are no dead airspaces; and
(cc)
have an aggregate fixed open area of greater than or equal to 1% of the ceiling area; or
(B)
having—
(aa)
not less than 2 wind-driven roof ventilators having an aggregate opening area of greater than or equal to 0.14 m2; and
(bb)
gable vents, ridge vents, eave vents, roof vents or the like that have an aggregate fixed open area of greater than or equal to 0.2% of the ceiling area.
Table 3.12.1.1a Roof—minimum Total R-values (climate zone 1)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Down | ≤ 0.4 | 3.1 |
| Down | > 0.4 but ≤ 0.6 | 4.1 |
| Down | > 0.6 | 5.1 |
Table 3.12.1.1b Roof—minimum Total R-values (climate zone 2—altitude less than 300 m)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Down | ≤ 0.4 | 4.1 |
| Down | > 0.4 but ≤ 0.6 | 4.6 |
| Down | > 0.6 | 5.1 |
Note to Table 3.12.1.1b: Altitude means the height above the Australian Height Datum at the location where the building is to be constructed.
Table 3.12.1.1c Roof—minimum Total R-values (climate zone 2—altitude 300 m or more)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Down and Up | ≤ 0.4 | 4.1 |
| Down and Up | > 0.4 but ≤ 0.6 | 4.6 |
| Down and Up | > 0.6 | 5.1 |
Note to Table 3.12.1.1c: Altitude means the height above the Australian Height Datum at the location where the building is to be constructed.
Table 3.12.1.1d Roof—minimum Total R-values (climate zone 3)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Down and Up | ≤ 0.4 | 4.1 |
| Down and Up | > 0.4 but ≤ 0.6 | 4.6 |
| Down and Up | > 0.6 | 5.1 |
Table 3.12.1.1e Roof—minimum Total R-values (climate zones 4 and 5)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Up | ≤ 0.4 | 4.1 |
| Up | > 0.4 but ≤ 0.6 | 4.6 |
| Up | > 0.6 | 5.1 |
Table 3.12.1.1f Roof—minimum Total R-values (climate zones 6 and 7)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Up | ≤ 0.4 | 4.6 |
| Up | > 0.4 but ≤ 0.6 | 5.1 |
| Up | > 0.6 | 5.1 |
Table 3.12.1.1g Roof—minimum Total R-values (climate zone 8)
| Direction of heat flow | Upper surface solar absorptance value | Minimum Total R-Value |
|---|---|---|
| Up | ≤ 0.4 | 6.3 |
| Up | > 0.4 but ≤ 0.6 | 6.3 |
| Up | > 0.6 | 6.3 |
Explanatory information:
Explanatory information:
- The term ‘as appropriate’ used in reference to Tables 3.12.1.1a to 3.12.1.1g, means the table used must be appropriate to the climate zone in which the building is to be located.
- The roof space ventilation option, in climate zones 1, 2, 3, 4 and 5, applies to a pitched roof with a flat ceiling to ensure that efficient cross ventilation is achieved in the roof space to remove hot air. Roof space ventilation is generally not suitable for most flat, skillion, cathedral ceiling and similar roof types because of the lack of space between the ceiling and roof.
- Care should be taken to ensure that the roof ventilation openings do not allow rain penetration and that they comply with appropriate bushfire provisions.
- Gaps between roof tiles with sarking (or reflective insulation at rafter level) and metal sheet roofing are not acceptable methods of providing roof space ventilation.
- Compliance with the ventilation provisions in 3.12.1.2(b)(ii) may result in the ingress of wind driven rain, fine dust, corrosive aerosols,or stimulate the growth of mould or fungus in the roof enclosure. Consideration should therefore be given to the surrounding environmental features, including exposure to marine or industrial environments, prior to adopting this as an alternative to the roof insulation provisions in 3.12.1.2(b)(i)(B).
- A low solar absorptance roof reduces the flow of heat from solar radiation better than a high solar absorptance roof. A roof with a solar absorptance value of less than 0.4 typically corresponds to a roof of light colour such as white, off-white or cream. Typical absorptance values based on ASTM E903 are as follows.
| Colour | Value |
|---|---|
| Slate (dark grey) | 0.90 |
| Red, green | 0.75 |
| Yellow, buff | 0.60 |
| Zinc aluminium — dull | 0.55 |
| Galvanised steel — dull | 0.55 |
| Light grey | 0.45 |
| Off white | 0.35 |
| Light cream | 0.30 |
(c)
A roof that—
(i)
is required to achieve a minimum Total R-Value; and
(ii)
has metal sheet roofing directly fixed to metal purlins, metal rafters or metal battens; and
(iii)
does not have a ceiling lining or has a ceiling lining fixed directly to those metal purlins, metal rafters or metal battens (see Figure 3.12.1.1(b)),
must have a thermal break, consisting of a material with an R-Value of greater than or equal to 0.2, installed between the metal sheet roofing and its supporting metal purlins, metal rafters, or metal battens.
(d)
A roof, or roof and associated ceiling,is deemed to have the Total R-Value in Figure 3.12.1.1.
Figure 3.12.1.1 Total R-Value for typical roof and ceiling construction
3.12.1.1(a) Flat roof, skillion roof and cathedral ceiling with a ceiling lining under rafter
Unventilated with a downwards direction of heat flow — Total R-Value of 0.48
Unventilated with an upwards direction of heat flow — Total R-Value of 0.36
3.12.1.1(b) Flat roof, skillion roof and cathedral ceiling with exposed rafters
Unventilated with a downwards direction of heat flow — Total R-Value of 0.44
Unventilated with an upwards direction of heat flow — Total R-Value of 0.38
3.12.1.1(c) Tiled pitched roof with flat ceiling
Ventilated with a downwards direction of heat flow — Total R-Value of 0.74
Ventilated with an upwards direction of heat flow — Total R-Value of 0.23
Unventilated with a downwards direction of heat flow — Total R-Value of 0.56
Unventilated with an upwards direction of heat flow — Total R-Value of 0.41
3.12.1.1(d) Metal pitched roof with flat ceiling
Ventilated with a downwards direction of heat flow — Total R-Value of 0.72
Ventilated with an upwards direction of heat flow — Total R-Value of 0.21
Unventilated with a downwards direction of heat flow — Total R-Value of 0.54
Unventilated with an upwards direction of heat flow — Total R-Value of 0.39
Notes to Figure 3.12.1.1:
- The Total R-Value of the roof and ceiling construction in Figure 3.12.1.1 is based on there being a roof space. If the roof space is filled, the roof space R-Value needs to be subtracted from the Total R-Value of the roof and ceiling materials.
- The Total R-Value of the unventilated roof and ceiling construction in Figure 3.12.1.1(c) for tiled roofs are based on there being sarking-type material which would prevent ventilation of the roof space through the gaps in the roof tiles.
Explanatory information:
Explanatory information:
- Typical construction:
Figure 3.12.1.1 provides examples of various roof and ceiling construction. The R-Value of the required insulation is calculated by subtracting the inherent Total R-Value of the roof and ceiling construction from the Total R-Value in Tables 3.12.1.1a to 3.12.1.1g. The inherent Total R-Value of the typical roof and ceiling has been determined by adding together the R-Values of the out door air film, roof cladding, roof airspace, ceiling sheet lining and internal film.
-
The Total R-Value of the roof and ceiling materials may need to be adjusted if other building elements such as sarking are also installed. For example, sarking or sheet insulation under tiles may change a roof space from “ventilated” to “unventilated”.
- Thermal bridging:
Irrespective of the framing material used, the minimum added R-Value specified in Figures 3.12.1.1 and 3.12.1.3 and Table 3.12.1.4 is deemed to include the effect of thermal bridging created by framing members in situations other than described in explanatory note 4.
- Thermal break:
Because of the high thermal conductance of metal, a thermal break is to be provided where the ceiling lining of a house is fixed directly to the underside of the metal purlins or metal battens of a metal deck roof or where there is no ceiling lining. The purpose of the thermal break is to ensure that the thermal performance of this form of roof construction is comparable to that of a similar roof with timber purlins or timber battens.
A thermal break may be provided by materials such as timber, expanded polystyrene strips, plywood or compressed bulk insulation. The material used as a thermal break must separate the metal purlins or metal battens from the metal deck roofing and achieve the specified R-Value. Reflective insulation alone is not suitable for use as a thermal break because it requires an adjoining airspace to achieve the specified R-Value (see explanatory note 6).
For the purposes of 3.12.1.2(c),expanded polystyrene strips of not less than 12 mm thickness,compressed bulk insulation, and timber of not less than 20 mm thickness are considered to achieve an R-Value of not less than 0.2.
- Location of insulation:
The thermal performance of the roof may vary depending on the position of the insulation, the climatic conditions, the design of the house and the way in which it is operated. For example, insulation installed under the roof, rather than on the ceiling, of a conditioned house with a large roof space is less effective because of the additional volume of roof airspace that would need to be heated or cooled. Conversely, for an unconditioned house, the use of reflective insulation is more effective when placed directly under the roof.
-
Choice of insulation:
There are a number of different insulation products that may be used to achieve the minimum added R-Value. However, care should be taken to ensure that the choice made is appropriate for the construction and climatic conditions as the location and relationship between options in Figures 3.12.1.1 and 3.12.1.3 and Table 3.12.1.4 may not be suitable in all circumstances for both practical and technical reasons. For instance, in some climate zones, insulation should be installed with due consideration of condensation and associated interaction with adjoining building materials. As an example, reflective insulation or sarking installed on the cold side of the building envelope should be vapour permeable. Note that Part 3.8.7 contains specific provisions for condensation.
Reflective insulation is considered to provide the following additional R-Values when used in conjunction with the Total R-Value of a pitched roof and flat ceiling construction described in Figure 3.12.1.1. To achieve these values, the reflective insulation must be laid directly under the roof cladding and have a minimum airspace of 15 mm between a reflective side of the reflective insulation and the adjoining lining or roof cladding (see 3.12.1.1(b)).
The actual R-Value added by reflective insulation and its adjoining airspace should be determined for each product in accordance with relevant standards, taking into consideration factors such as the number of adjacent airspaces, dimensions of the adjacent airspace, whether the space is ventilated and the presence of an anti-glare coating. When reflective insulation has an anti-glare coating on one side, the emittance value of that side will be greater than the value of the uncoated side.
Also, where another emittance value for reflective insulation is used (other than the value used in the table below), care should be taken to ensure that the number of airspaces allowed for is consistent with the form of construction and whether the airspace is reflective, partially reflective or non-reflective. Where bulk insulation fill is the airspace, the Total R-Value should be reduced to take account of the loss of airspace.
R-Value added by reflective insulation—Pitched roof (>10°) with horizontal ceiling
| Emittance of added reflective insulation | Direction of heat flow Note 1 | R-Value added—unventilated roof space | R-Value added—ventilated roof space |
|---|---|---|---|
| 0.2 outer / 0.05 inner | Down | 1.12 | 1.21 |
| 0.2 outer / 0.05 inner | Up | 0.75 | 0.59 |
| 0.9 outer / 0.05 inner | Down | 0.92 | 1.01 |
| 0.9 outer / 0.05 inner | Up | 0.55 | 0.40 |
R-Value added by reflective insulation—Flat skillion or pitched roof (≤10°) with horizontal ceiling
| Emittance of added reflective insulation | Direction of heat flow Note 1 | R-Value added |
|---|---|---|
| 0.2 outer / 0.05 inner | Down | 1.28 |
| 0.2 outer / 0.05 inner | Up | 0.68 |
| 0.9 outer / 0.05 inner | Down | 1.06 |
| 0.9 outer / 0.05 inner | Up | 0.49 |
R-Value added by reflective insulation—Pitched roof with cathedral ceilings
| Emittance of added reflective insulation | Direction of heat flow Note 1 | R-Value added — pitch ≥ 15° to ≤ 25° | R-Value added — pitch > 25° to ≤ 35° | R-Value added — pitch > 35° to ≤ 45° |
|---|---|---|---|---|
| 0.2 outer / 0.05 inner | Down | 0.96 | 0.86 | 0.66 |
| 0.2 outer / 0.05 inner | Up | 0.72 | 0.74 | 0.77 |
| 0.9 outer / 0.05 inner | Down | 0.74 | 0.64 | 0.44 |
| 0.9 outer / 0.05 inner | Up | 0.51 | 0.52 | 0.53 |
Notes:
- The required direction of heat flow applicable in each of the climate zones specified in Tables 3.12.1.1a to 3.12.1.1g.
- Ventilated roof space means ventilated in accordance with 3.12.1.2(b).
(e)
Where, for operational or safety reasons associated with exhaust fans, flues or recessed downlights, the area of required ceiling insulation is reduced, the loss of insulation must be compensated for by increasing the R-Value of insulation in the remainder of the ceiling in accordance with Table 3.12.1.1h.
(f)
Where the minimum R-Value of ceiling insulation required to satisfy 3.12.1.2(a) is not stated in Table 3.12.1.1h, interpolation may be used to determine the adjusted minimum R-Value.
Table 3.12.1.1h Adjustment of minimum R-Value for loss of ceiling insulation
| Percentage of ceiling area uninsulated | Minimum R-Value of ceiling insulation required to satisfy 3.12.1.2(a) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 | 4.5 | 5.0 | 5.5 | 6.0 | |
| Minimum R-Value of ceiling insulation required to satisfy 3.12.1.2(a) | |||||||||||
| 0.5% to less than 1.0% | 1.0 | 1.6 | 2.2 | 2.8 | 3.4 | 4.0 | 4.7 | 5.4 | 6.2 | 6.9 | X |
| 1.0% to less than 1.5% | 1.1 | 1.7 | 2.3 | 2.9 | 3.6 | 4.4 | 5.2 | 6.1 | 7.0 | X | X |
| 1.5% to less than 2.0% | 1.1 | 1.7 | 2.4 | 3.1 | 3.9 | 4.8 | 5.8 | 6.8 | X | X | X |
| 2.0% to less than 2.5% | 1.1 | 1.8 | 2.5 | 3.3 | 4.2 | 5.3 | 6.5 | X | X | X | X |
| 2.5% to less than 3.0% | 1.2 | 1.9 | 2.6 | 3.6 | 4.6 | 5.9 | X | X | X | X | X |
| 3.0% to less than 4.0% | 1.2 | 2.0 | 3.0 | 4.2 | 5.7 | X | X | X | X | X | X |
| 4.0% to less than 5.0% | 1.3 | 2.2 | 3.4 | 5.0 | X | X | X | X | X | X | X |
| 5.0% or more | X | X | X | X | X | X | X | X | X | X | X |
Notes to Table 3.12.1.1h:
- X = not permitted
- Where the minimum R-Value of ceiling insulation required to satisfy 3.12.1.2(a) is greater than or equal to 6.0, adjustment to compensate for loss of ceiling insulation area is not permitted.
Explanatory information:
Explanatory information:
- When considering the reduction of insulation because of exhaust fans, flues or recessed downlights,0.5% of the ceiling area for a 200m2 house would permit 2 bathroom heater-light assemblies, a laundry exhaust fan, a kitchen exhaust fan and either approximately 20 recessed down-lights with 50 mm clearance to insulation, 10 recessed downlights with 100mm clearance to insulation or only 3 recessed downlights with 200mm clearance to insulation.
- Note that Table 3.12.1.1h refers to the R-Value of the insulation located on the ceiling and not the Total R-Value required of the roof. The roof has an inherent R-Value and there may also be insulation at the roof line.
- Note that 3.12.1.2(e) does not require an increase in ceiling insulation for roof lights.
- Placing some of the required insulation at the roof level may result in a more practical outcome. Insulation at the roof level is effective in warm climates and significantly moderates the roof space extremes and condensation risk in cold climates. Note that Part 3.8.7 contains specific provisions for condensation.
3.12.1.3 Roof lights
(a)
Roof lights (including any associated shaft and diffuser) serving a habitable room or an interconnecting space such as a corridor, hallway, stairway or the like must—
(i)
if the roof lights are not required for compliance with Part 3.8.4 or —
(A)
comply with Table 3.12.1.2; and
(B)
have an aggregate area of not more than 3% of the total floor area of the storey served; or
(ii)
if the roof lights are required for compliance with Part 3.8.4 or Part 3.8.5—
(A)
have an area not more than 150% of the minimum area required by Part 3.8.5; and
(B)
have transparent and translucent elements, including any imperforate ceiling diffuser with—
(aa)
a Total System SHGC of not more than 0.29; and
(bb)
a Total system U-Valueof not more than 2.9.
(b)
For the purposes of Table 3.12.1.2, the following applies:
(i)
The roof light shaft index is determined by measuring the distance from the centre of the shaft at the roof to the centre of the shaft at the ceiling level and dividing it by the average internal dimension of the shaft opening at the ceiling level (or the diameter for a circular shaft) in the same units of measurement.
(ii)
The roof light area index is the total area of roof lights serving the room or space as a percentage of the floor area of the room or space.
(iii)
The total area of roof lights is the combined area for all roof lights serving the room or space.
(iv)
The area of a roof light is the area of the roof opening that allows light to enter the building.
(v)
The thermal performance of an imperforate ceiling diffuser may be included in the Total system U-Valueof the roof light.
(c)
The total area of roof lights serving the room or space as a percentage of the floor area of the room or space must not be more than 5% unless allowed by (a)(ii),
Table 3.12.1.2 Roof lights – thermal performance of transparent and translucent elements
| Roof light shaft index | Roof light area index ≤ 2% | Roof light area index > 2% to ≤ 3% | Roof light area index > 3% to ≤ 4% | Roof light area index > 4% to ≤ 5% |
|---|---|---|---|---|
| <0.5 |
Total System SHGC ≤0.83 Total system U-Value ≤8.5 |
Total System SHGC ≤0.57 Total system U-Value ≤5.7 |
Total System SHGC ≤0.43 Total system U-Value ≤4.3 |
Total System SHGC ≤0.34 Total system U-Value ≤3.4 |
| ≥0.5 to <1.0 |
Total System SHGC ≤0.83 Total system U-Value ≤8.5 |
Total System SHGC ≤0.72 Total system U-Value ≤5.7 |
Total System SHGC ≤0.54 Total system U-Value ≤4.3 |
Total System SHGC ≤0.43 Total system U-Value ≤3.4 |
| ≥1.0 to <2.5 |
Total System SHGC ≤0.83 Total system U-Value ≤8.5 |
Total System SHGC ≤0.83 Total system U-Value ≤5.7 |
Total System SHGC ≤0.69 Total system U-Value ≤4.3 |
Total System SHGC ≤0.55 Total system U-Value ≤3.4 |
| ≥2.5 |
Total System SHGC ≤0.83 Total system U-Value ≤8.5 |
Total System SHGC ≤0.83 Total system U-Value ≤5.7 |
Total System SHGC ≤0.83 Total system U-Value ≤4.3 |
Total System SHGC ≤0.83 Total system U-Value ≤3.4 |
Explanatory information:
Explanatory information:
- The Total System SHGC and Total system U-Values are expressed as Australian Fenestration Rating Council (AFRC) values.
- The Total System SHGC and Total system U-Values are for a roof light with or without a ceiling diffuser. A roof light may achieve the required performance on its own or in conjunction with a ceiling diffuser.
- The Total System SHGC and Total system U-Values for some simple types of roof lights are shown in the table below. Lower U-Value figures represent higher thermal resistance. Lower SHGC figures represent less solar heat transmission. The table gives worst case assessments, which can be improved by obtaining generic or custom product assessments from suppliers, manufacturers, industry associations (including their online resources) and from competent assessors.
Worst case whole roof light element performance values without a ceiling diffuser or with a perforated ceiling diffuser
| Translucent or transparent element description | Domed panel | Flat, framed panel |
|---|---|---|
| Single layer clear |
Total System SHGC: 0.80 Total system U-Value: 8.4 |
Total System SHGC: 0.79 Total system U-Value: 8.0 |
| Single tinted |
Total System SHGC: 0.66 Total system U-Value: 8.4 |
Total System SHGC: 0.63 Total system U-Value: 7.9 |
| Single layer translucent (“opal”) |
Total System SHGC: 0.57 Total system U-Value: 8.4 |
Total System SHGC: 0.56 Total system U-Value: 7.9 |
| Double layer clear |
Total System SHGC: 0.71 Total system U-Value: 5.4 |
Total System SHGC: 0.70 Total system U-Value: 4.9 |
Worst case whole roof light element performance values with an imperforate ceiling diffuser
| Translucent or transparent element description | Domed panel | Flat, framed panel |
|---|---|---|
| Single layer clear |
Total System SHGC: 0.72 Total system U-Value: 4.3 |
Total System SHGC: 0.71 Total system U-Value: 4.2 |
| Single tinted |
Total System SHGC: 0.59 Total system U-Value: 4.3 |
Total System SHGC: 0.57 Total system U-Value: 4.2 |
| Single layer translucent (“opal”) |
Total System SHGC: 0.51 Total system U-Value: 4.3 |
Total System SHGC: 0.50 Total system U-Value: 4.2 |
| Double layer clear |
Total System SHGC: 0.64 Total system U-Value: 3.4 |
Total System SHGC: 0.63 Total system U-Value: 3.2 |
3.12.1.4 External walls
(a)
Each part of an external wall must satisfy the requirements of —
(i)
(b) for all walls; or
(ii)
(c) for walls with a surface density greater than or equal to 220 kg/m2, except for—
(A)
opaque non-glazed openings such as doors (including garage doors), vents, penetrations, shutters and the like; and
Explanatory information:
Explanatory information:
Surface density is the mass of one vertical square metre of wall.
(b)
Each part of an external wall must—
(i)
in climate zones 1, 2, 3, 4 and 5—
(A)
achieve a minimum Total R-Value of 2.8; or
(B)
—
(aa)
achieve a minimum Total R-Value of 2.4; and
(bb)
shade the external wall of the storey with a verandah, balcony, eaves, carport or the like, which projects at a minimum angle of 15 degrees in accordance with Figure 3.12.1.2; or
(ii)
in climate zones 6 and 7, achieve a minimum Total R-Value of 2.8; or
(iii)
in climate zones 8, achieve a minimum Total R-Value of 3.8.
(c)
Each part of an external wall with a wall surface density of greater than or equal to 220 kg/m2 must—
(i)
in climate zones 1, 2 and 3—
(A)
for a storey, other than one with a storey above, shade the wall with a verandah, balcony, eaves, carport or the like that projects at a minimum angle of 15 degrees in accordance with Figure 3.12.1.2; and
(B)
(C)
incorporate insulation with an R-Value of greater than or equal to 0.5; and
(D)
on the lowest storey containing habitable rooms, have either—
(aa)
a concrete slab-on-ground floor; or
(bb)
masonry internal walls; or
(ii)
in climate zone 5 (option a)—
(A)
for a storey, other than one with a storey above, shade the wall with a verandah, balcony, eaves, carport or the like that projects at a minimum angle of 15 degrees in accordance with Figure 3.12.1.2; and
(B)
when the external walls are not shaded in accordance with (A)and there is another storey above,external glazing complies with 3.12.2.1 with the applicable value for CSHGC in Table 3.12.2.1e reduced by 15%;and
(C)
incorporate insulation with an R-Value of greater than or equal to 0.5; and
(D)
on the lowest storey containing habitable rooms, have either—
(aa)
a concrete slab-on-ground floor; or
(bb)
masonry internal walls; or
(iii)
in climate zone 5 (option b)—
(A)
shade the wall with a verandah, balcony, eaves, carport or the like that projects at a minimum angle of 15 degrees in accordance with Figure 3.12.1.2; and
(B)
have external glazing that complies with 3.12.2.1 with the applicable value for CSHGC in Table 3.12.2.1e reduced by 15%; and
(C)
on the lowest storey containing habitable rooms, have either—
(aa)
a concrete slab-on-ground floor; or
(bb)
masonry internal walls; or
(iv)
in climate zones 4 and 6 (option a)—
(A)
(B)
incorporate insulation with an R-Value of greater than or equal to 0.5; and
(C)
on the lowest storey containing habitable rooms, have either—
(aa)
a concrete slab-on-ground floor; or
(bb)
masonry internal walls; or
(v)
in climate zones 4 and 6 (option b), have external glazing that complies with 3.12.2.1 with the applicable value for CU in Tables 3.12.2.1d and 3.12.2.1f reduced by 20%; or
(vi)
in climate zones 4 and 6 (option c)—
(A)
incorporate insulation with an R-Value of greater than or equal to 1.0; and
(B)
on the lowest storey containing habitable rooms, have either—
(aa)
a concrete slab-on-ground floor; or
(bb)
masonry internal walls; or
(vii)
in climate zone 7 (option a)—
(A)
(B)
incorporate insulation with an R-Value of greater than or equal to 1.0; or
(viii)
in climate zone 7 (option b)—
(A)
(B)
incorporate insulation with an R-Value of greater than or equal to 0.5; or
(ix)
in climate zone 7 (option c), incorporate insulation with an R-Value of greater than or equal to 1.5; or
(x)
in climate zone 8, achieve a minimum Total R-Value of 3.8.
Figure 3.12.1.2 Measurement of a projection for wall shading
Explanatory information:
Explanatory information:
Guttering can be considered as providing shading if attached to a shading projection.
(d)
A wall in (b) that—
(i)
has lightweight external cladding such as weatherboards, fibre-cement or metal sheeting fixed to the metal frame; and
(ii)
does not have a wall lining or has a wall lining that is fixed directly to the metal frame (see Figure 3.12.1.3(a) and (b)),
must have a thermal break, consisting of a material with an R-Value greater than or equal to 0.2, installed between the external cladding and the metal frame.
Explanatory information:
Explanatory information:
- The thermal performance of metal and timber-framed walls is affected by conductive thermal bridging by the framing members and convective thermal bridging at gaps between the framing and any added bulk insulation. Metal framed walls are more prone to conductive thermal bridging than timber-framed walls.
- Because of the high thermal conductance of metal, a thermal break is needed when a metal framing member directly connects the external cladding to the internal lining or the internal environment. The purpose of the thermal break is to ensure that the thermal performance of the metal framed wall is comparable to that of a similarly clad timber-framed wall.
A thermal break may be provided by materials such as timber battens, plastic strips or polystyrene insulation sheeting.The material used as a thermal break must separate the metal frame from the cladding and achieve the specified R-Value.
For the purposes of 3.12.1.4(d)(ii), expanded polystyrene strips greater than or equal to 12 mm thickness and timber greater than or equal to 20 mm thickness are deemed to achieve an R-Value greater than or equal to 0.2.
The R-Value of the thermal break is not included when calculating the Total R-Value of the wall, if the thermal break is only applied to the metal frame, because this calculation is done for locations free of framing members.
(e)
A wall in constructed in accordance with Figure 3.12.1.3 is deemed to have the Total R-Value specified in that Figure
Figure 3.12.1.3 Total R-Value for typical wall construction
3.12.1.3(a) Weatherboard external wall construction — Total R-Value of 0.48
3.12.1.3(b) Fibre-cement sheet external wall construction — Total R-Value of 0.42
3.12.1.3(c) Clay masonry veneer external wall construction — Total R-Value of 0.56
3.12.1.3(d) — Concrete blockwork masonry external wall construction — Total R-Value of 0.54
3.12.1.3(e) Cavity clay masonry external wall construction — Total R-Value of 0.69
3.12.1.3(f) Externally insulated clay masonry (reverse clay masonry veneer) external wall construction — Total R-Value of 0.53
3.12.1.3(g) Externally insulated concrete masonry external wall construction — Total R-Value of 0.46
3.12.1.3(h) Autoclaved aerated concrete masonry external wall construction — Total R-Value of 2.42
Explanatory information:
Explanatory information:
- Figure 3.12.1.3 provides examples of typical types of wall construction. The additional R-Value required can be calculated by subtracting the inherent Total R-Value of the typical wall construction in Figure 3.12.1.3 from the required Total R-Value.The inherent Total R-Value of the typical wall construction has been arrived at by adding together the R-Values for outdoor air film, wall cladding or veneer, wall cavity or airspace, internal lining and internal air film. Where a cavity or airspace is filled the Total R-Value should be reduced by 0.17 to take account for the loss of the cavity or airspace.
- Reflective insulation with one reflective surface having an emittance and direction as indicated, is considered to achieve the following R-Values when used in conjunction with the Total R-Value of a wall construction, as described in Figure 3.12.1.3. The actual R-Value added by reflective insulation should be determined for each product in accordance with the standard prescribed in 3.12.1.1(a), which takes into consideration factors such as the number of adjacent airspaces, dimensions of the adjacent airspace, whether the airspace is ventilated and the presence of an anti-glare coating.
Explanatory information for R-Value added by reflective insulation
| Wall construction | Reflective airspace details | R-Value added by reflective insulation |
|---|---|---|
| Concrete or masonry with internal plasterboard on battens |
One 20 mm reflective airspace located between reflective insulation (of not more than 0.05 emittance inwards) and plasterboard | 0.48 |
| External wall cladding (70 mm timber frame with internal lining) | One 70 mm reflective airspace located between reflective insulation (of not more than 0.05 emittance inwards) and plasterboard | 0.43 |
| Masonry veneer (70 mm timber frame with internal lining) |
|
0.95 |
| Cavity masonry |
|
0.50 |
The following are examples of some typical wall constructions that achieve a surface density of 220 kg/m2:
- Two leaves each of 90 mm thick or greater clay or concrete masonry.
- 140 mm thick or greater dense-weight hollow concrete or clay blocks with—
- 10 mm plasterboard or render; and
- at least one concrete grouted horizontal bond beam; and
- vertical cores filled with concrete grout at centres not exceeding 1000 mm.
- 140 mm thick or greater concrete wall panels and dense-weight hollow concrete or clay blocks with all vertical cores filled with concrete grout.
- 190 mm thick or greater dense-weight hollow concrete or clay blocks with—
- at least one concrete grouted horizontal bond beam; and
- vertical cores filled with concrete grout at centres not exceeding 1800 mm.
- Earth-wall construction with a minimum wall thickness of 200 mm.
3.12.1.5 Floors
(a)
A suspended floor, other than an intermediate floor in a building with more than one storey—
(i)
must achieve the Total R-Value specified in Table 3.12.1.4; and
Table 3.12.1.4 Suspended floor – minimum Total R-Value
| Climate zone | Direction of heat flow | Minimum Total R-Value |
|---|---|---|
| 1 | Up | 1.5 |
| 2 | Up | 1.0 |
| 3 | Up | 1.5 |
| 4 | Down | 2.25 |
| 5 | Down | 1.0 |
| 6 | Down | 2.25 |
| 7 | Down | 2.75 |
| 8 | Down | 3.25 |
Note to Table 3.12.1.4: For an enclosed perimeter treatment, the under floor airspace and its enclosure may be included in the Total R-Value calculation.
(ii)
with an in-slab or in-screed heating or cooling system, must be insulated—
(A)
around the vertical edge of its perimeter with insulation having an R-Value greater than or equal to 1.0; and
(iii)
that is enclosed beneath, must have a barrier installed at or below floor level to prevent convection within the wall cavity, from the airspace under the floor.
Explanatory information:
Explanatory information:
- An enclosed perimeter treatment means that the airspace under the floor is enclosed between ground and floor level by walls which have only the required subfloor vents.
- The barrier required by 3.12.1.5(a)(iii) could be an imperforate flashing.
- Specific solutions for concrete slab and timber floors can be found in documents and online resources prepared by industry associations and product suppliers.
(b)
A floor is deemed to have the Total R-Value specified in Tables 3.12.1.5a and 3.12.1.5b.
Table 3.12.1.5a Total R-Value for typical suspended timber floor
| Enclosure and height of floor and direction of heat flow | Cavity masonry | 190 mm concrete masonry | Single skin masonry | 9 mm fibre-cement sheet |
|---|---|---|---|---|
| Enclosed ≤0.6 m high with an upwards heat flow | Total R-Value: 1.00 | Total R-Value: 0.93 | Total R-Value: 0.88 | Total R-Value: 0.77 |
| Enclosed ≤0.6 m high with a downwards heat flow | Total R-Value: 1.11 | Total R-Value: 1.06 | Total R-Value: 1.01 | Total R-Value: 0.90 |
| Enclosed >0.6 m but to ≤1.2 m high with an upwards heat flow |
Total R-Value: 0.86 |
Total R-Value: 0.81 | Total R-Value: 0.76 | Total R-Value: 0.65 |
| Enclosed >0.6 m but to ≤1.2 m high with a downwards heat flow | Total R-Value: 1.00 | Total R-Value: 0.94 | Total R-Value: 0.89 | Total R-Value: 0.77 |
| Enclosed >1.2 m to ≤2.4 m high with an upwards heat flow | Total R-Value: 0.76 | Total R-Value: 0.72 | Total R-Value: 0.67 | Total R-Value: 0.57 |
| Enclosed >1.2 m to ≤2.4 m high with a downwards heat flow | Total R-Value: 0.89 | Total R-Value: 0.84 | Total R-Value: 0.79 | Total R-Value: 0.69 |
| Unenclosed with an upwards heat flow | Total R-Value: 0.39 | Total R-Value: 0.39 | Total R-Value: 0.39 | Total R-Value: 0.39 |
| Unenclosed with a downwards heat flow | Total R-Value: 0.51 | Total R-Value: 0.51 | Total R-Value: 0.51 | Total R-Value: 0.51 |
Notes to Tables 3.12.1.5a:
- The height of the floor is measured from ground surface to the underside of the floor or the insulation.
- For the purposes of calculating the Total R-Value of a floor, the R-Value attributable to an in-slab or in-screed heating or cooling system is ignored.
Table 3.12.1.5b Total R-Value for typical suspended concrete floor
| Enclosure and height of floor and direction of heat flow | Cavity masonry | 190 mm concrete masonry | Single skin masonry | 9 mm fibre-cement sheet |
|---|---|---|---|---|
| Enclosed ≤0.6 m high with an upwards heat flow | Total R-Value: 0.93 | Total R-Value: 0.88 | Total R-Value: 0.83 | Total R-Value: 0.72 |
| Enclosed ≤0.6 m high with a downwards heat flow | Total R-Value: 1.06 | Total R-Value: 1.01 | Total R-Value: 0.96 | Total R-Value: 0.85 |
| Enclosed >0.6 m but to ≤1.2 m high with an upwards heat flow |
Total R-Value: 0.81 |
Total R-Value: 0.76 | Total R-Value: 0.71 | Total R-Value: 0.60 |
| Enclosed >0.6 m but to ≤1.2 m high with a downwards heat flow | Total R-Value: 0.94 | Total R-Value: 0.89 | Total R-Value: 0.84 | Total R-Value: 0.72 |
| Enclosed >1.2 m to ≤2.4 m high with an upwards heat flow | Total R-Value: 0.71 | Total R-Value: 0.67 | Total R-Value: 0.62 | Total R-Value: 0.52 |
| Enclosed >1.2 m to ≤2.4 m high with a downwards heat flow | Total R-Value: 0.84 | Total R-Value: 0.79 | Total R-Value: 0.74 | Total R-Value: 0.64 |
| Unenclosed with an upwards heat flow | Total R-Value: 0.34 | Total R-Value: 0.34 | Total R-Value: 0.34 | Total R-Value: 0.34 |
| Unenclosed with a downwards heat flow | Total R-Value: 0.46 | Total R-Value: 0.46 | Total R-Value: 0.46 | Total R-Value: 0.46 |
Notes to Tables 3.12.1.5b:
- The height of the floor is measured from ground surface to the underside of the floor or the insulation.
- For the purposes of calculating the Total R-Value of a floor, the R-Value attributable to an in-slab or in-screed heating or cooling system is ignored.
Explanatory information:
Explanatory information:
- Tables 3.12.1.5a and 3.12.1.5b provide examples of the inherent Total R-Values of enclosed and unenclosed suspended floors of two typical types of construction. Any added R-Value can be calculated by subtracting the inherent R-Value of the typical construction in Tables 3.12.1.5a and 3.12.1.5b from the required Total R-Value in Table 3.12.1.4.
- Any non-reflective building membrane fixed between or under floor joists is considered to add an R-Value of 0.2 to the Total R-Value of the base construction described in Tables 3.12.1.5a and 3.12.1.5b. Reflective insulation will achieve a higher value which will need to be determined for each product in accordance with relevant standards. Typically, a reflective building membrane attached beneath the floor joists of an unenclosed floor, with a single bright side facing upwards to a 90 mm airspace, can add an R-Value of 0.43 for heat flow upwards and 1.32 for heat flow downwards. Double sided reflective insulation with a 90 mm airspace installed under an enclosed floor can add an R-Value of 0.55 for heat flow upwards and 1.97 for heat flow downwards. Both examples allow for dust on the upper surface.
- A reflective or non-reflective building membrane should be installed with due consideration of potentially damaging condensation in some climate zones and associated interaction with adjoining building materials.
- For further information on reflective insulation, refer to the explanatory information accompanying Figure 3.12.1.1.
(c)
A concrete slab-on-ground—
(i)
with an in-slab or in-screed heating or cooling system, must have insulation with an R-Value greater than or equal to 1.0, installed around the vertical edge of its perimeter; and
(d)
Insulation required by (c)(i) and (c)(ii)(A) must—
(i)
be water resistant; and
(ii)
be continuous from the adjacent finished ground level—
(A)
to a depth of greater than or equal to 300 mm; or
(B)
for at least the full depth of the vertical edge of the concrete slab-on-ground (see Figure 3.12.1.4).
Explanatory information:
Explanatory information:
3.12.1.5(e) provides an exemption for an in-screed heating or cooling system used solely in bathrooms, amenity areas and the like, as these are typically small areas.
Figure 3.12.1.4 Insulation of slab edge
Explanatory information:
Explanatory information:
Care should be taken to ensure that the type of termite management system selected is compatible with the slab edge insulation.
3.12.1.6 Attached Class 10a buildings
A Class 10a building attached to a Class 1 building must—
(a)
have an external fabric that achieves the required level of thermal performance for a Class 1 building; or
(b)
be separated from the Class 1 building with construction having the required level of thermal performance for the Class 1 building; or
(c)
in climate zone 5—
(i)
be enclosed with masonry walls other than where there are doors and glazing; and
(ii)
be separated from the Class 1 building with a masonry wall that extends to the ceiling or roof; and
(iii)
achieve a Total R-Value in the roof equivalent to that required by Tables 3.12.1.1a to 3.12.2.1h as appropriate for the Class 1 building; and
(iv)
not have a garage door facing the east or west orientation other than if the Class 1 building glazing complies with 3.12.2.1 with the applicable value for CSHGC in Tables 3.12.2.1a to 3.12.2.1h as appropriate reduced by 15%.
Explanatory information:
Explanatory information:
The attachment of a Class 10a building, such as a garage, glasshouse, solarium, pool enclosure or the like should not compromise the thermal performance of the Class 1 building. In addition, the Class 10a building may be insulated and so assist the Class 1 building achieve the required thermal performance.
The following are examples of a Class 1 building with an attached Class 10a garage.
In (a), the thermal performance required for the Class 1 building may be achieved by including the walls and floor of the Class 1 building that adjoin the Class 10a garage.
In (b), the thermal performance required for the Class 1 building may be achieved by including the outside walls and floor of the Class 10a garage.
In (c),in climate zone 5, the thermal performance of the Class 1 building may be achieved by ensuring that the roof of the Class 10a building satisfies Tables 3.12.1.1a to 3.12.1.1g and the walls are of masonry construction.
