NCC 2022 Volume One - Building Code of Australia Class 2 to 9 buildings

36

Specification 36 Material properties

Specification 36 Material properties

This Specification lists the thermal properties of some common construction materials.

To clarify that Specification 36 covers the relevant properties attributed to common construction materials, air films and airspaces, and reflective surfaces.

(1) Tables S36C2a, S36C2b, S36C2c, S36C2d and S36C2e list the thermal conductivity considered to be achieved by some common construction materials.

(2) For the purposes of Tables S36C2a, S36C2b, S36C2c, S36C2d and S36C2e:

  1. For materials which incorporate cores or hollows in regular patterns (such as cored brickwork, hollow blockwork and cored floor or wall panels), the tabulated material densities and thermal conductivities are based on the gross density (mass divided by external dimensions).
  2. The R-Value of a material is determined by dividing the thickness of the material in metres by the thermal conductivity in Wm-1K-1.

(3) Tables S36C2f, S36C2g, S36C2h, S36C2i, S36C2j, S36C2k, S36C2l and S36C2m list the R-Value considered to be achieved by air films and airspaces.

(4) For an envelope that contains a ventilated airspace, the Total R-Value of the building fabric must be reduced based on the area of ventilation openings in accordance with clause 6.3 of AS/NZS 4859.2.

(5) The requirements of (4) do not apply to a roof with an airspace greater than 300 mm or a pitched roof greater than 5° with a horizontal ceiling.

Table S36C2a Thermal conductivity of typical framing materials
Description Density (kg/m3) Thermal conductivity (Wm-1K-1)
Steel 7850 47.5
Timber – kiln dried hardwood (across the grain) 677 0.16
Timber – Radiata pine (across the grain) 506 0.12
Table S36C2b Thermal conductivity of typical roof cladding materials
Description Density (kg/m3) Thermal conductivity (Wm-1K-1)
Aluminium sheeting 2680 210
Concrete or terra cotta tiles 1922 0.81
Steel sheeting 7850 47.5
Table S36C2c Thermal conductivity of typical wall cladding materials
Description Density (kg/m3) Thermal conductivity (Wm-1K-1)
Aluminium sheeting 2680 210
Autoclaved aerated concrete 350 0.10
510 0.15
900 0.27
Cement render (1 part cement to 4 parts sand) 1570 0.53
Clay brick: 2.75 kg 1430 0.55
Clay brick: 3.25 kg 1690 0.65
Clay brick: 3.75 kg 1950 0.78
Concrete block: 190 mm dense or 90 mm dense solid 1100/2200 1.1
Concrete block: 140 mm dense or 190 mm lightweight 1250/910 0.85
Concrete block: 90 mm dense hollow or 90 mm lightweight solid 1650 / 1800 0.75
Concrete block: 140 mm lightweight 1050 0.67
Concrete block: 90 mm lightweight 1360 0.55
Fibre-cement 1360 0.25
Gypsum plasterboard 880 0.17
Pine weatherboards 506 0.10
Plywood 530 0.14
Solid concrete 2400 1.44
Steel sheeting 7850 47.5
Prestressed hollow core concrete panel 1680 0.80
Table S36C2d Thermal conductivity of typical flooring materials
Description Density (kg/m3) Thermal conductivity (Wm-1K-1)
Carpet underlay - 0.04
Carpet - 0.05
Prestressed hollow core concrete planks 1680 0.80
Particleboard 640 0.12
Plywood 530 0.14
Timber – kiln dried hardwood (across the grain) 677 0.16
Timber – Radiata pine (across the grain) 506 0.10
Solid concrete 2400 1.44
Vinyl floor tiles 2050 0.79
Table S36C2e Thermal conductivity of other materials not listed in Tables S36C2a to S36C2d
Description Density (kg/m3) Thermal conductivity (Wm-1K-1)
Clay soil (10% moisture content) 1300 0.6
PMMA (polymethylmethacrylate) 1180 1.0
Polycarbonates 1200 0.2
Sand (6% moisture content) 1800 1.64
Soda lime glass 2500 1.0
Table S36C2f Typical R-Values for air films: surfaces other than outdoor surfaces
Position of air film Direction of heat flow R-Value
On a surface with a pitch of not more than 5° Up 0.11
Down 0.16
On a surface with a pitch of more than 5° but not more than 30° Up 0.11
Down 0.15
On a surface with a pitch of more than 30° but not more than 45° Up 0.11
Down 0.13
On a wall Horizontal 0.12
Table S36C2g Typical R-Values for air films: outdoor surfaces
Position of air film Direction of heat flow R-Value
Any Any 0.03
Table S36C2h Typical R-Values for airspaces: non-reflective non-ventilated
Position of airspace Direction of heat flow R-Value
In a roof with a pitch not more than 5° or cathedral ceiling with a 20 mm to 50 mm thick roof airspace Up 0.15
Down 0.15
In a roof with a pitch not more than 5° or cathedral ceiling with a more than 50 mm to 300 mm thick roof airspace Up 0.15
Down 0.17
In a roof airspace greater than 300 mm thick or with a horizontal ceiling and a roof pitch more than 5° Up 0.18
Down 0.28
In a wall Horizontal 0.16
Table Notes
  1. Linear interpolation may be used to calculate the R-Value of the airspace in a roof with an intermediate pitch.
  2. A non-ventilated airspace in a roof is one with continuous cover, such as metal or sarked tiles, and no specific provision for ventilation.
  3. R-Values are calculated using AS/NZS 4859.2 based on the following:
    1. summer temperatures of 24°C internally and 36°C externally for heat transfer down; and
    2. winter temperatures of 18°C internally and 12°C externally for heat transfer up; and
    3. average of summer and winter results for horizontal heat transfer (e.g. in walls).
  4. A non-ventilated airspace in a wall is one where there is no express provision for airflow through it and openings to the external environment do not exceed more than 500 mm2 per metre of length in the horizontal direction.
  5. A non-ventilated airspace in a wall for the purposes of Note (4) includes a wall with drainage openings or weepholes that are open vertical joints in the outer leaf of a cavity masonry wall, which are not regarded as ventilation openings.
Table S36C2i Typical R-Values for airspaces: reflective non-ventilated
Position of airspace Direction of heat flow R-Value
In a wall with an inner reflective surface of 0.05 emittance and a 20 mm to 100 mm airspace to the wall lining Horizontal 0.61
In a wall with a central reflective membrane with an inner surface emittance of 0.05 and a 20 mm to 100 mm airspace from the membrane to the wall lining, and an outer anti-glare emittance of 0.08 and a 20 mm to 100 mm airspace to the wall cladding Horizontal 1.1
In a wall with an outer anti-glare reflective surface of 0.08 emittance and a 20 mm to 100 mm airspace to the wall cladding Horizontal 0.53
Table Notes
  1. A non-ventilated airspace in a wall is one where there is no express provision for airflow through it and openings to the external environment do not exceed 500 mm2 per metre of length in the horizontal direction.
  2. A non-ventilated airspace in a wall for the purposes of Note (1) includes a wall with drainage openings or weepholes that are open vertical joints in the outer leaf of a cavity masonry wall, which are not regarded as ventilation openings.
  3. R-Values are calculated using AS/NZS 4859.2 based on the following:
    1. summer temperatures of 24°C internally and 36°C externally for heat transfer down; and
    2. winter temperatures of 18°C internally and 12°C externally for heat transfer up; and
    3. average of summer and winter results for horizontal heat transfer (e.g. in walls); and
    4. emittances are normal emittances of bounding surfaces in accordance with AS 4200.1.
Table S36C2j Typical R-Values for airspaces: non-reflective ventilated
Position of airspace Direction of heat flow R-Value
In a roof airspace greater than 300 mm thick or with a horizontal ceiling and a pitch more than 5° Up Nil
Down 0.46
Table S36C2k Typical R-Values for roof spaces with a reflective surface: Roof space > 300 mm thick or pitched roof with a horizontal ceiling
Direction of heat flow R-Value of reflective airspace
Ventilated roof space Non-ventilated roof space
Up 0.34 0.56
Down 1.36 1.09
Table Notes
  1. A non-ventilated airspace in a roof is one with continuous cover, such as metal or sarked tiles, and no specific provision for ventilation.
  2. A reflective surface is a surface with normal emittance of 0.05 or less, in accordance with AS 4200.1.
Table S36C2l Typical R-Values for non-ventilated roof spaces with a reflective surface: Flat, skillion or pitched roof (≤5°) with horizontal ceiling, roof space not more than 300 mm thick
Emittance of airspace bounding surfaces Thickness of roof space Direction of heat flow R-Value of reflective airspace
Surface 1 emittance 0.9, Surface 2 emittance 0.05 ≤ 300 mm Up 0.43
Surface 1 emittance 0.9, Surface 2 emittance 0.05 20 mm Down 0.60
Surface 1 emittance 0.9, Surface 2 emittance 0.05 60 mm Down 1.16
Surface 1 emittance 0.9, Surface 2 emittance 0.05 100 mm to ≤ 300 mm Down 1.30
Table Notes
  1. A non-ventilated airspace in a roof is one with continuous cover, such as metal, and no specific provision for ventilation.
  2. Linear interpolation may be used to calculate the R-Value of an airspace of intermediate thickness.
  3. R-Values are calculated using AS/NZS 4859.2 based on the following:
    1. summer temperatures of 24°C internally and 36°C externally for heat transfer down; and
    2. winter temperatures of 18°C internally and 12°C externally for heat transfer up; and
    3. emittances are normal emittances of bounding surfaces in accordance with AS 4200.1.
Table S36C2m Typical R-Values for non-ventilated roof spaces with a reflective surface: Pitched roof with cathedral ceiling, roof space not more than 300 mm thick
Emittance of airspace bounding surfaces Thickness of roof space Direction of heat flow R-Value of reflective airspace
15° to not more than 25° pitch more than 25° to not more than 35° pitch more than 35° to not more than 45° pitch
Surface 1 emittance 0.9, Surface 2 emittance 0.05 ≤ 300 mm Up 0.43 0.43 0.43
Surface 1 emittance 0.9, Surface 2 emittance 0.05 20 mm Down 0.59 0.59 0.59
Surface 1 emittance 0.9, Surface 2 emittance 0.05 60 mm Down 0.91 0.82 0.75
Surface 1 emittance 0.9, Surface 2 emittance 0.05 100 mm to ≤ 300 mm Down 0.96 0.85 0.76
Table Notes
  1. A non-ventilated airspace in a roof is one with continuous cover, such as metal or sarked tiles, and no specific provision for ventilation.
  2. Linear interpolation may be used to calculate the R-Value of the airspace in a roof with an intermediate pitch.
  3. R-Values are calculated using AS/NZS 4859.2 based on the following:
    1. summer temperatures of 24°C internally and 36°C externally for heat transfer down; and
    2. winter temperatures of 18°C internally and 12°C externally for heat transfer up; and
    3. emittances are normal emittances of bounding surfaces in accordance with AS 4200.1.

Explanatory information

Section F of NCC Volume One may require ventilation of roof space in climate zones 6, 7 and 8 to manage risks associated with condensation.

To detail the relevant properties attributed to common construction materials, air films and airspaces, and reflective surfaces.

The values provided in Tables S36C2a to S36C2e are material density values and thermal conductivity (k) values for common construction materials. Tables S36C2f to S36C2m list the R-Values of airspaces and air films, and expected added R-Values provided by a reflective surface. All except the material density can be used in determining the Total R-Value of a roof, wall or floor system.

The term surface density suggests mass per unit volume but in this context is the mass of the full thickness of 1 square metre of wall surface area.

S36C2(4) explains the meaning of a ventilated roof space.