> For the complete documentation index, see [llms.txt](https://docs.betterbuilding.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.betterbuilding.io/user-guide/workflows/energy-efficiency/part-j4-building-fabric/part-j4-info/j4d4-roof-and-ceiling-construction.md).

# J4D4 Roof and Ceiling Construction

## What is J4D4 Roof and Ceiling Construction?

J4D4 Roof and ceiling construction outlines the thermal performance requirements for roofs and ceilings based on different climate zones:

1. **Climate Zones 1, 2, 3, 4, and 5**: The roof or ceiling must achieve a Total R-Value of **R3.7** for heat flowing downward.
2. **Climate Zone 6**: The requirement is slightly reduced, with the roof or ceiling needing to achieve a Total R-Value of **R3.2** for heat flowing downward.
3. **Climate Zone 7**: In this colder zone, the Total R-Value requirement is **R3.7** for heat flowing upward.
4. **Climate Zone 8**: The highest thermal resistance is required here, with a Total R-Value of **R4.8** for upward heat flow.

Additionally, in Climate Zones 1 through 7, the solar absorptance of the upper surface of the roof must not exceed 0.45. This limits the amount of solar heat absorbed by the roof, further enhancing the building’s energy efficiency.

## J4D4 Roof and Ceiling Construction on Better Building

Speckel automatically checks the provisions of J4D4 Roof and Ceiling Construction against your design, while providing AS/NZS 4859.2 calculations within our Roof applications. 


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