NCC 2016 Volume One
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Specification J1.2 Material Properties

Specification J1.2 Material Properties

1. Scope

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

Intent

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

2. Construction Deemed-to-Satisfy

(a)

Table 2a lists the thermal conductivity considered to be achieved by some common construction materials.

Table 2a THERMAL CONDUCTIVITY OF TYPICAL WALL, ROOF/CEILING AND FLOOR MATERIALS

Material description Material density kg/m3 Thermal conductivity W/m.K
1. Framing
(a) Steel 7850 47.5
(b) Timber – kiln dried hardwood (across the grain) 677 0.16
(c) Timber – Radiata pine (across the grain) 506 0.10
2. Roof Cladding
(a) Aluminium sheeting 2680 210
(b) Concrete or terra cotta tiles 1922 0.81
(c) Steel sheeting 7850 47.5
3. Wall Cladding
(a) Aluminium sheeting 2680 210
(b) Autoclaved aerated concrete 350 0.10
900 0.27
(c) Cement render (1 cement : 4 sand) 1570 0.53
(d) Clay bricks
(i) Clay brick – 2.75 kg 1430 0.55
(ii) Clay brick – 3.25 kg 1690 0.65
(iii) Clay brick – 3.75 kg 1950 0.78
(e) Concrete blocks
(i) 190 mm dense or 90 mm dense solid 1100/2200 1.1
(ii) 140 mm dense or 190 mm lightweight 1250/910 0.85
(iii) 90 mm dense hollow or 90 mm lightweight solid 1650/1800 0.75
(iv) 140 mm lightweight 1050 0.67
(iv) 90 mm lightweight 1360 0.55
(f) Fibre-cement 1360 0.25
(g) Gypsum plasterboard 880 0.17
(h) Pine weatherboards 506 0.10
(i) Plywood 530 0.14
(j) Solid concrete 2400 1.44
(k) Steel sheeting 7850 47.5
(l) Prestressed hollow core concrete panel 1680 0.80
4. Flooring Materials
(a) Carpet underlay - 0.04
(b) Carpet - 0.05
(c) Prestressed hollow core concrete planks 1680 0.80
(d) Particleboard 640 0.12
(e) Plywood 530 0.14
(f) Timber – kiln dried hardwood (across the grain) 677 0.16
(g) Timber – Radiata pine (across the grain) 506 0.10
(h) Solid concrete 2400 1.44
(i) Vinyl floor tiles 2050 0.79
5. Other Materials
(a) Clay soil (10% moisture content) 1300 0.6
(b) PMMA (polymethylmethacrylate) 1180 1.00
(c) Polycarbonates 1200 0.2
(d) Sand (6% moisture content) 1800 1.64
(e) Soda lime glass 2500 1.0

Notes:

  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 W/m.K.
(b)

Table 2b lists the R-Values considered to be achieved by air films and airspaces.

Table 2b TYPICAL R-VALUES FOR AIRSPACES AND AIR FILMS

Position of airspace Direction of heat flow R-Value
1. Airspaces non-reflective unventilated
In a roof with a pitch of not more than 5° Up 0.15
Down 0.22
In a roof with a ceiling that is parallel with a roof with a pitch more than 5° and not more than 15° Up 0.15
Down 0.21
In a roof with a ceiling that is parallel with a roof with a pitch more than 22° and not more than 45° Up 0.15
Down 0.18
In any roof space with a horizontal ceiling, with a pitch more than 5° Up 0.18
Down 0.28
In a wall Horizontal 0.17
2. Airspaces non-reflective ventilated
In any roof with a pitch not more than 5° and 100 mm deep airspace Up Nil
Down 0.19
In any roof space with a horizontal ceiling, with a pitch more than 5° Up Nil
Down 0.46
In a wall Horizontal 0.14
3. Air films – Still air
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° and not more than 30° Up 0.11
Down 0.15
On a surface with a pitch of more than 30° and not more than 45° Up 0.11
Down 0.13
On a wall Horizontal 0.12
4. Air films – Moving air
Not more than 3 m/s wind Any direction 0.04
More than 3 m/s wind speed and not more than 7 m/s wind speed Any direction 0.03

Note:R-Values are for a temperature of 10°C and temperature difference of 15K.
(c)

The thermal properties considered to be achieved by reflective surfaces are—

(i)

within a wall—

(A)

with an inner reflective surface of 0.05 emittance and a 20 mm airspace to the wall lining, an added R-Value of 0.48; and

(B)

with an inner reflective surface of 0.05 emittance and a 70 mm airspace to the wall lining, an added R-Value of 0.43; and

(C)

with an inner reflective surface of 0.05 emittance and a 70 mm airspace to the wall lining and an outer anti-glare reflective surface of 0.20 emittance and a 25 mm airspace to the wall cladding, an added R-Value of 0.95; and

(D)

with an outer anti-glare reflective surface of 0.20 emittance and a 35 mm airspace to the wall cladding, an added R-Value of 0.50; and

(ii)

within a roof where the reflective insulation is laid directly under the roof, those in Table 2c.

Table 2c TYPICAL THERMAL PROPERTIES FOR REFLECTIVE SURFACES WITH AIRSPACES IN ROOFS

Emittance of added reflective insulation Direction of heat flow R-Value added by a reflective surface
Pitched roof (>10°) with horizontal ceiling Flat, skillion or pitched roof (≤10°) with horizontal ceiling Pitched roof with cathedral ceiling
Ventilated roof space Non-ventilated roof space 15° to not more than 25° pitch more than 25° to not more than 35° pitch more than 35° to 45° pitch

0.2 outer

0.05 inner

 Downwards 1.21
 1.12
 1.28
 0.96
 0.86
 0.66

0.2 outer

0.05 inner

 Upwards 0.59 0.75 0.68 0.72 0.74 0.77

0.9 outer

0.05 inner

 Downwards 1.01 0.92 1.06 0.74 0.64 0.44

0.9 outer

0.05 inner

 Upwards 0.40 0.55 0.49 0.51 0.52 0.53
(d)

A ventilated roof space is a roof space with—

(i)

gable vents, ridge vents, eave vents, roof vents or the like that—

(A)

are evenly distributed to allow an unobstructed flow of air; and

(B)

are located to ensure, where practicable, there are no dead airspaces; and

(C)

have an aggregate fixed open area of not less than 1.0% of the ceiling area; or

(ii)

not less than 2 wind-driven roof ventilators having an aggregate opening area of not less than 0.14 m2 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; or

(iii)

a tiled roof without sarking-type material at roof level.

Intent

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

The values provided in are material density values (used in determining if a wall system exceeds 220 kg/m2) and thermal conductivity (k) values for materials. and list the R-Values of airspaces and films and expected added R-Values provided by a reflective surface. All except the material density are 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.

explains the meaning of a ventilated roof space.