Roof Restoration · Six guides · Sheet 2
Roof colour · Your Home and NCC Part 13.2Roof colour and heat
Your Home, the Australian Government’s guide to sustainable homes, says light-coloured roofing limits the radiant heat that flows into the roof space, and advises light-coloured roofs in every climate zone except the alpine zone, where it advises dark ones; and the National Construction Code caps how much sunlight a roof’s upper surface may absorb in climate zones 1 to 5.
General information, not design advice for your home. Your Home and the NCC’s energy efficiency provisions are the places to check.
Solar absorptance, in a sentence
The code works with a roof’s solar absorptance, written SA in its tables, and defines total solar reflectance as the complement of solar absorptance: a roof with an SA of 0.64 has a total solar reflectance of 0.36.
Its rule is one line long: “In climate zones 1 to 5, the solar absorptance of the upper surface of a roof must not be more than 0.64.” The same line appears in the 2022 edition, which Queensland uses until it adopts NCC 2025 on 1 May 2027. NSW is the exception: its own version of the clause has no colour limit, as the panel explains.
What Your Home advises, climate zone by climate zone
The NCC divides Australia into 8 climate zones. Your Home’s design advice for each zone includes a line on roof colour, and in seven of the eight it advises a light-coloured roof.
| Zone | Climate | Your Home on roof colour | NCC limit on SA |
|---|---|---|---|
| 1 | Hot humid summer, warm winter | Use light colours on roofs and walls | 0.64 or less |
| 2 | Warm humid summer, mild winter | Light-coloured roof and wall materials | 0.64 or less |
| 3 | Hot dry summer, warm winter | Light-coloured roof materials | 0.64 or less |
| 4 | Hot dry summer, cool winter | Light-coloured roof materials | 0.64 or less |
| 5 | Warm temperate | Light-coloured roof materials | 0.64 or less |
| 6 | Mild temperate | Light-coloured roof materials | No limit in 13.2.3(10) |
| 7 | Cool temperate | Light-coloured roof materials | No limit in 13.2.3(10) |
| 8 | Alpine | Dark-coloured roof and wall materials | No limit in 13.2.3(10) |
To find your zone, Your Home describes where each one runs: zone 5, for example, takes in the coastal strip of NSW from Wollongong through Sydney to Newcastle, and zone 6 includes Melbourne and Ballarat. Its climate zones page has the full descriptions.
A lighter roof can mean less ceiling insulation
The colour rule is not the only place SA appears. The code’s tables of minimum ceiling insulation are split into SA bands, so a darker roof can call for more insulation under the deemed-to-satisfy route.
NCC 2025 Table 13.2.3a covers a single-storey house in climate zone 1 with a pitched roof and a flat ceiling. Take the row for a vented roof with reflective insulation under the roof and under-roof insulation below R1.0. The table counts a roof as vented if, for example, it has one wind-driven roof ventilator per 50 m² of ceiling area, with gable, eave or ridge vents.
- SA 0.23 or less
- R1.5
- Over 0.23, up to 0.32
- R2.0
- Over 0.32, up to 0.42
- R2.5
- Over 0.42, up to 0.53
- R3.0
- Over 0.53, up to 0.64
- R3.5
Minimum ceiling insulation for that one row. For a roof that is not vented, without reflective insulation and with under-roof insulation below R1.0, the same table lists R3.5 for the lightest band and marks every darker band “not permitted”. Other zones and roof types have their own tables.
Heat that comes through a metal sheet
- Colour and foil work together. Your Home says foil insulation and light-coloured roofing limit the radiant heat that flows into the roof space, and that a well-ventilated roof space acts as a buffer between inside and out, at the part of a house that is hardest to shade.
- Vents and fans need a light roof to work well. Your Home says pulling hot air out of the roof space works best under a light-coloured roof or a cool roof that is already keeping heat out, and that a dark or bare steel roof takes in too much heat for most fans and vents to swap it for outside air.
- Cool roofs are made for it. Among its ideas for coping with heatwaves, Your Home lists light-coloured roofs and cool roof technology: roofing materials and coatings designed to have high solar reflectance and thermal emittance.
- Solar panels gain a little. Light-coloured roofs, important for reducing heat gain, also slightly improve the efficiency of solar panels, according to Your Home.