The roof is one of the biggest surfaces on a house. It faces the sun all day and soaks up a lot of heat in summer. The colour you pick for it changes how hot the roof space gets. That heat then works its way down into the rooms below.
Roof colour is often chosen for looks alone. It is worth thinking about comfort and running costs at the same time. A good choice can suit the style of the house and still keep it cooler. This guide covers how roof colour affects heat and what to weigh up before you decide.
What solar absorptance means
The key measure is called solar absorptance. It describes how much of the sunlight hitting the roof is absorbed by the material. The rest is reflected away. The NSW Planning Portal guide to solar absorptance explains that a roof with lower absorptance reflects more heat and keeps the roof space and home cooler on a hot day.
Absorptance is given as a number between 0 and 1. A value of 0 would mean the roof absorbs nothing and a value of 1 would mean it absorbs everything. The NSW BASIX scheme groups roofs into three bands. Light roofs sit below 0.475, medium roofs sit between 0.475 and 0.7 and dark roofs sit above 0.7.
Lighter colours usually have lower absorptance than darker ones. That is the simple rule most people remember. But colour alone does not tell the whole story. Two products that look alike can have quite different values, so the actual figure matters.
How much difference roof colour makes
Houses with a low absorptance roof heat up less over summer. Albury City Council notes that these homes need less air conditioning as a result. That means lower power bills in the hottest months. It also means rooms that feel more bearable when the power is off or the cooling is struggling.
The South Australian Government has published findings from studies of suburban rooftops. One 2018 heat mapping report on the northern suburbs found light roofed houses were 4.3°C cooler than average during the day. Dark roofed houses in the same study were 4.6°C hotter than average. A 2017 report on the western suburbs found a similar pattern in roof surface temperatures.
The effect goes past the property line. Dark roofs draw in and hold heat, which adds to the urban heat island effect in built up suburbs. Where whole streets choose dark roofs, the whole neighbourhood can end up hotter. Lighter roofs help the street as well as the house underneath them.
Rules that may apply to your roof colour
Some states now look at roof colour as part of approvals. In NSW, roofing makers have been asked to provide a solar absorptance value for each colour. Certifiers use that figure to check the roof against the commitments on the BASIX certificate. If your design relies on a light roof, the colour you order needs to match.
The South Australian Government announcement on light coloured roofs says dark roofs will be removed from future stages of the Playford Alive development. It also links National Construction Code changes in that state with steps such as better glazing and insulation and moving away from dark roof and wall colours. Rules differ between states and estates, so check your local requirements early.
Many new estates also have their own design guidelines. These can limit roof colours, materials and pitch. Read them before you fall in love with a particular finish. It is far easier to adjust a plan at the drawing stage than after the roofing has been ordered.
Balancing looks and comfort
A light roof does not have to look plain. Pale greys, soft creams and warm off whites can suit many house styles. Some darker looking colours now come in versions with special coatings. The NSW guide notes that spectrally selective surfaces can lower absorptance for a given colour.
Think about how the roof works with the rest of the outside of the house. Walls, gutters, fascias and window frames all need to sit well together. Your garden plays a part too. If you are planning new beds and trees, our notes on landscape design on a budget cover simple ways to add shade and softness around the house.
It also helps to look at colour inside and outside as one plan. Light tones can make a room feel open and airy, as covered in our guide to making your kitchen look and feel bigger. Outside, a lighter roof can make the whole house look calmer. Bring samples home and view them in morning and afternoon light before you decide.
Glare and your neighbours
A common worry is that a light roof will throw glare at the house next door. The NSW guide says a lighter roof does not have to cause more glare. A roof can have low solar absorptance and low light reflection at the same time. If glare is a concern, ask about these options when comparing products.
Roof pitch and the height of nearby homes play a part as well. A low pitched roof below a neighbour’s upstairs windows is more likely to be seen. Matt finishes tend to look softer than glossy ones. Talk through the setting with your builder or designer before you settle on a finish.
Other ways to keep heat out
Roof colour works best as part of a wider plan. Insulation in the ceiling slows heat moving from the roof space into the rooms. Shading on windows keeps direct sun off the glass. Ventilation in the roof space can help clear hot air on summer afternoons.
Outdoor areas matter too. Hard surfaces near the house can store heat and radiate it back at the walls. Decks, paths and paving all respond differently in strong sun. Our answers to common questions about Millboard decking look at one outdoor surface in more detail.
Plants can make a big difference over time. Trees and climbers can shade walls and windows. They also cool the air around the house as they grow. Before you start digging, read up on the common problems with DIY landscape design so the new garden supports the house rather than fighting it.
A quick checklist before you choose
- Ask for the solar absorptance value of each colour you are considering.
- Check your BASIX, energy rating or estate rules for any colour limits.
- Look at large samples on site at different times of day.
- Ask about low glare finishes if you overlook neighbours.
- Plan insulation, shading and ventilation alongside the roof.
Frequently asked questions
Is a white roof always the coolest?
Pale roofs generally absorb less sunlight than dark ones. The exact result depends on the product and its coating. Always compare the solar absorptance figure rather than relying on how a colour looks. That number gives a fairer comparison between brands.
Can I repaint an existing roof a lighter colour?
Many roofs can be recoated in a lighter shade. Some councils also suggest reflective roof paints as a way to cut summer heat. Use a qualified roof painter and a product made for your roof type. Check any estate rules or heritage controls before you change the colour.
Does roof colour matter if the ceiling is insulated?
Yes, both work together. Insulation slows the heat that builds up in the roof space. A lighter roof means less heat builds up there in the first place. Using both gives better results than either one on its own.
Where do I find a roof colour’s absorptance value?
Roofing makers often list the value in their colour charts or technical sheets. In NSW they have been asked to provide it for each colour. If you cannot find it, ask the supplier directly. Your energy assessor or certifier can also tell you which values work for your design.
