The level of insulation will depend on the climatic zone, building construction type, and    whether auxiliary heating and/or cooling is used.
           
The following deemed-to-satisfy rules are to be applied by the building owner at the design stage of the building if he chooses not to consider a rational design option. A roof and/orceiling   that are part of the building envelope must achieve the Total R-Value as specified in SANS 10400-XA for the direction of heat flow.
               
The following table below gives typical data and deemed-to-satisfy thicknesses of generic insulation products in accordance with SANS 204 Energy efficiency in buildings.
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Recommended Levels of Insulation To Achieve Deemed-To-Satisfy Rule for Energy Efficiency in an Unventilated Roof And Ceiling Construction
Climate Zones
1
2
3
4
5
6
Minimum required Total R-value (m².K/W) (for roof solar absorptance of more than 0.55)
3.7
3.2
2.7
3.7
2.7
3.5
Direction of heat flow
Up
Up
Down and Up
Up
Down
Up
Estimated Total R-Value (m².K/W) of roof and ceiling materials(Roof covering & plasterboard only)
0.35 - 0.40
0.41 - 0.53
0.35 – 0.40
Estimated Minimum added R-Value of Insulation (m².K/W)
2.30 – 3.35
2.15 – 2.29
3.10 – 3.15
Generic Insulation Products
Density Kg/m³
Thermal Conductivity
W/(m.k.)
Recommended deemed-to-satisfy min thickness (mm) of insulation product
Cellulose Fibre Loose-Fill
27.5
0.040
135
115
100
135
100
130
Flexible Fibre Glass Blanket
10-18
0.040
135
115
100
135
100
130
Flexible BOQ Polyester Fibre Blanket
24
0.038
130
110
90
130
90
125
Flexible Polyester Blanket
11.5
0.046
160
140
120
160
110
150
Flexible Mineral/Rockwool
60-120
0.033
115
100
80
115
80
100
Flexible Ceramic Fibre
84
0.033
115
100
80
115
80
100
Rigid Expanded Polystyrene (EPS)SD
15
*0.035
120
100
90
120
80
115
Rigid Extruded Polystyrene (XPS)
32
*0.028
100
80
70
100
65
90
Rigid Fibre Glass Board
47.5
0.033
115
100
80
115
80
100
Rigid BOQ Polyester Fibre Board
61
0.034
115
100
80
115
80
110
Rigid Polyurethane Board
32
*0.025
85
70
60
85
60
80
NOTE The deemed-to-satisfy recommended levels of insulation can be achieved by the use of reflective foils, bulk insulation or rigid board insulation or in combination with one another. Maximum efficiency may be achieved at reduced thicknesses taking the aforementioned into account.
(*)Thermal efficiencies are dependent on materials thickness, density, age, operating temperature and moisture
R-Values Considered to be achieved by Reflective Foil Laminates (refer BCA 2007)
Emittance of added reflective insulation
Direction of heat flow
R-Value added by reflective foil insulation
Pitched roof (=10°) with horizontal ceiling
Flat skillion or pitched roof (=10°) with horizontal ceiling
Pitched roof with cathedral ceilings
Naturalventilated roof space
Non-ventilated roof space
22° pitch
30° pitch
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
Note: (a) Reflective foil insulation values inclusive of 15mm air gap. Reflective insulation should work in conjunction with and air gap to be effective. (b) The R-Value of reflective insulation is affected by the airspace between a reflective side of the reflective insulation and the building lining or cladding. Dust build-up reduces R-Values.