NCC 2016 Volume One
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Specification J1.5 Wall Construction

Specification J1.5 Wall Construction

1. Scope

This Specification describes the thermal performance of some common forms of external wall construction.

Intent

To clarify that outlines the thermal performance of some of the more common forms of wall construction.

2. Construction Deemed-to-Satisfy

Figure 2 details the R-Values considered to be achieved by some common forms of wall construction.

Figure 2 TYPICAL R-VALUES FOR WALL CONSTRUCTION

External wall construction description Item Item description R-Value
(a) Masonry veneer – 25 mm to 50 mm cavity, 10 mm internal plaster on 90 mm stud frame
v1_SpecJ15A_2005.svg
 1. Outdoor air film (7 m/s) 0.04
2. Masonry (See Notes 3 and 4) 0.09
3. Cavity and airspace (115 to 140 mm, made up of 90 mm stud + 25 mm to 50 mm airspace non-reflective and unventilated) 0.17
4. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
5. Indoor air film (still air) 0.12
Total R-Value 0.48
(b) Cavity masonry – 20 mm to 50 mm cavity, 10 mm internal plaster on battens or furring channels
v1_SpecJ15B_2005.svg
 1. Outdoor air film (7 m/s) 0.04
2. Masonry (See Notes 3 and 4) 0.09
3. Masonry cavity (20 mm to 50 mm, non-reflective and unventilated) 0.17
4. Masonry (See Note 4) 0.09
5. Airspace (20 mm to 35 mm, non-reflective and unventilated) 0.17
6. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
7. Indoor air film (still air) 0.12
Total R-Value 0.74
(c) Dense weight hollow concrete block with internal plaster on battens or furring channels
v1_SpecJ15C_2006.svg
 1. Outdoor air film (7 m/s) 0.04
2. Dense weight hollow concrete block (See Notes 3 and 4) 0.15
3. Airspace (20 mm to 40 mm non-reflective and unventilated) 0.17
4. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
5. Indoor air film (still air) 0.12
Total R-Value 0.54
(d) 125 mm solid reinforced concrete (dense weight) – 10 mm internal plaster on battens or furring channels
v1_SpecJ15D_2006.svg
 1. Outdoor air film (7 m/s) 0.04
2. 125 mm minimum solid reinforced concrete (See Note 3) 0.09
3. Airspace (20 mm to 40 mm non-reflective and unventilated) 0.17
4. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
5. Indoor air film (still air) 0.12
Total R-Value 0.48
(e) Timber wall – external 6 mm cement sheet cladding, 90 mm stud frame, 10 mm plaster
v1_SpecJ15E_2005.svg
 1. Outdoor air film (7 m/s) 0.04
2. Fibre-cement (6 mm, 1360 kg/m3) 0.03
3. Airspace (90 mm nonreflective and unventilated) 0.17
4. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
5. Indoor air film (still air) 0.12
Total R-Value 0.42
(f) 200 mm autoclaved aerated concrete block – 10 mm internal plaster on battens or furring channels
v1_SpecJ15F_2005.svg
 1. Outdoor air film (7 m/s) 0.04
2. Autoclaved aerated concrete block (200 mm, 350 kg/m3) 2.00
3. Airspace (20 mm to 40 mm non-reflective and unventilated) 0.17
5. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
6. Indoor air film (still air) 0.12
Total R-Value 2.39
(g) 150 mm hollow-core concrete panels
– 10 mm internal plaster on battens or furring channels
v1_SpecJ15G_2005.svg
 1. Outdoor air film (7 m/s) 0.04
2. Prestressed hollow-core concrete panels (150 mm, 1,680 kg/m3, 30% cores) 0.14
3. Airspace (20 mm to 40 mm non-reflective and unventilated) 0.17
5. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
6. Indoor air film (still air) 0.12
Total R-Value 0.53
(h) Dense weight hollow concrete block with external 6 mm cement sheet cladding on battens or furring channels
v1_SpecJ15H_2006.svg
 1. Outdoor air film (7 m/s) 0.04
2. Fibre-cement (6 mm, 1360 kg/m3) 0.03
3. Airspace (20 mm to 40 mm non-reflective and unventilated) 0.17
4. Dense weight hollow concrete block (See Note 4) 0.15
5. 10 mm render 0.02
6. Indoor air film (still air) 0.12
Total R-Value 0.53
(i) Glazed construction within a metal frame – 10 mm internal plaster on battens or furring channels
v1_SpecJ15I_2014.svg
 1. Outdoor air film (7 m/s) 0.04
2. Clear or opaque glass (10 mm, 2500 kg/m3) 0.01
3. Airspace (20 mm to 40 mm non-reflective and unventilated) 0.17
4. Steel sheet (1 mm to 3 mm, 7850 kg/m3) 0.00
5. Airspace (2 mm to 100 mm non-reflective and unventilated) 0.17
6. Plasterboard, gypsum (10 mm, 880 kg/m3) 0.06
7. Indoor air film (still air) 0.12
Total R-Value 0.57

Notes:

  1. The R-Value of an item, other than an airspace, air film or air cavity, may be increased in proportion to the increased thickness of the item.
  2. TheTotal R-Value of a form of construction may be increased by the amount that an individual item is increased.
  3. The addition of 10 mm of render to a concrete or masonry wall will increase the Total R-Value by 0.02.
    1. The typical R-Value in Figure 2(a) and (b) is for 90 mm dense weight concrete block.
    2. The typical R-Value in Figure 2(c) and (h) is for 140 mm dense weight hollow concrete block.
    3. The typical R-Value in Figure 2(d) is for 125 mm solid reinforced concrete (2400 kg/m3).
    4. Other typical R-Values for masonry and concrete are as follows and may be substituted for those above:

      90 mm clay brick:
      (density 1430 kg/m3) 0.16
      (density 1690 kg/m3) 0.14
      (density 1950 kg/m3) 0.12
      110 mm clay brick:
      (density 1430 kg/m3, 2.75 kg/brick) 0.20
      (density 1690 kg/m3, 3.25 kg/brick) 0.17
      (density 1950 kg/m3, 3.75 kg/brick) 0.14
      Dense weight hollow concrete block:
      110 mm 0.12
      190 mm 0.20
    5. The Total R-Values in this Figure are for external walls. The Total R-Value for an internal wall of the same construction would be 0.08 greater because the R-Value for an outdoor air film would be replaced by that of an indoor air film.
    6. Where a cavity or airspace is filled, the R-Value listed for the cavity must be deducted from the Total R-Value of the wall.
Intent

To detail the Total R-Values considered to be achieved by common forms of wall construction.

provides examples of typical insulation locations in various types of wall construction. The Total R-Value required is achieved by adding the R-Value of the basic wall and the R-Value of any additional insulation incorporated. The Total R-Value of the typical wall construction has been produced by adding together the R-Values for outdoor air film, wall cladding, wall airspace, internal lining and internal air film.

The most common forms of construction for low-rise buildings are represented. It has not been possible to cover other forms of construction, particularly those used for high-rise construction, because of the wide range and the greater influence of winds, cyclones and earthquakes on the elements of the building. The Total R-Value of other forms of construction can be determined by adding the individual R-Values together.

For a material that is not listed as an item in , other than air, the R-Value may be determined by dividing the thickness of the item in metres by the thermal conductivity in W/m.K (typical values are described in ).

Reflective insulation that has just one reflective surface is considered to achieve the R-Values when used in conjunction with the Total R-Value of the common wall construction stated in . The actual R-Value added by reflective insulation should be determined for each product in accordance with the standards prescribed in the BCA, which take 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.

The width for any reflective airspaces adjacent to reflective insulation will not override other requirements such as minimum cavity requirements for masonry waterproofing.

Where a diagram shows reflective insulation or other insulation, these are indicative only. In some climates and using certain materials, neither may be necessary. In other cases, reflective insulation or insulation may be provided separately or in combination to give the required R-Value.

A minimum thickness of 70 mm is stated for framing. In some cases, the frame thickness may need to be increased to avoid compressing the bulk insulation and thus reducing its R-Value.

Walls with a surface density of 220 kg/m2 or more are deemed to achieve acceptable levels of thermal performance in certain climate zones due to their ability to store heat and therefore slow the heat transfer through the building fabric. These walls are defined by surface density (kg/m2) to reduce the complexity when measuring mass walls with voids.

Examples of some typical wall construction that achieve a surface density of 220 kg/m2 are provided in .