Specifiers
BCA Section J
Roof & Ceiling Construction BCA 2010 J1.3
- A roof or ceiling that is part of the envelop, other than of a sole-occupancy unit of a Class 2 building or a Class 4 part of a building, must achieve the Total R-Value specified in Table J1.3a for the direction of heat flow.
BCA 2010 Table J1.3a
Roofs & Ceilings - Minimum total R-Value for each climate zone.
| Climate zone | 1, 2 and 3 | 4, 5 and 6 | 7 | 8 |
|---|---|---|---|---|
| Direction of heat flow | Downwards | Upwards | ||
| Minimum Total R-Value for a roof or ceiling with a roof upper surface solar absorptance value of not more than 0.5 |
3.2 | 3.2 | 3.7 | 4.8 |
| Minimum Total R-Value for a roof or ceiling with a roof upper surface solar absorptance value of more than 0.5 but not more than 0.6 |
3.7 | 3.2 | 3.7 | 4.8 |
| Minimum Total R-Value for a roof or ceiling with a roof upper surface solar absorptance value of more than 0.6 |
4.2 | 3.2 | 3.7 | 4.8 |
Refer to BCA 2010 for full details on Section J compliance
Direction of Heat Flow
The direction of heat flow that predominates in each climate zone is also nominated in TableJ1.3a because it will have an impact on the performance of roof insulation systems.
Where “Downwards” is specified in Table J1.3a, this indicates that summer heat (a downwards heat flow into the building) is the major concern. An “Upwards” flow indicates that heat loss from the building during winter is the major concern.
A non-residential commercial building is likely to be air-conditioned and likely to have more day time use. The main heat flow direction for these buildings is therefore “Downwards” for all climate zones except 7 and 8.
Solar Absorptance for COLORBOND® Colours
Table 1 - Colour Classification in Accordance with the BCA
| Colour | Solar Absorptance |
|---|---|
| Classic Cream™ | 0.31 |
| Surfmist® | 0.318 |
| Paperbark® | 0.421 |
| Evening Haze® | 0.427 |
| Shale Grey™ | 0.433 |
| Sandbank® | 0.455 |
| Dune® | 0.466 |
| Windspray® | 0.584 |
| Pale Eucalypt® | 0.597 |
| Bushland® | 0.619 |
| Headland® | 0.632 |
| Wilderness® | 0.651 |
| Jasper® | 0.682 |
| Manor Red® | 0.688 |
| Woodland Grey® | 0.706 |
| Loft® | 0.711 |
| Monument® | 0.732 |
| Ironstone® | 0.743 |
| Cottage Green® | 0.746 |
| Deep Ocean® | 0.749 |
Refer to the COLORBOND® website for full details on solar absorptance
