Sub-Tropical Coastal

Recommended Levels of Insulation To Achieve Deemed-To-Satisfy Rule for Energy Efficiency in an Unventilated Roof And Ceiling Construction

Climate Zones 5
Minimum required Total R-value (m².K/W) (for roof solar absorptance of more than 0.55) 2.7
Direction of heat flow Down
Estimated Total R-Value (m².K/W) of roof and ceiling materials(Roof covering & plasterboard only) 0.41 – 0.53
Estimated Minimum added R-Value of Insulation (m².K/W) 2.15 – 2.29
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 0.040 100
Flexible Fibre Glass Blanket 10 – 18 0.040 100
Flexible BOQ Polyester Fibre Blanket 24 0.038 90
Flexible Polyester Blanket 11.5 0.046 110
Flexible Mineral/Rockwool 60-120 0.033 80
Flexible Ceramic Fibre 84 0.033 80
Rigid Expanded Polystyrene (EPS)SD 15 *0.035 80
Rigid Extruded Polystyrene (XPS) 32 *0.028 65
Rigid Fibre Glass Board 47.5 0.033 80
Rigid BOQ Polyester Fibre Board 61 0.034 80
Rigid Polyurethane Board 32 *0.025 60

(*)Thermal efficiencies are dependent on materials thickness, density, age, operating temperature and moisture. Thicknesses rounded-up to nearest production standard. This is a guideline for general design purpose only. For critical design purposes; i.e. rational design, contact manufacturers for actual R-values (Thermal Resistance (m²K/W)) and valid test reports.

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
Emittance of added reflective insulation Direction of heat flow 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 0.4 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.