A dark roof can drive up your energy bills

Article published 4 April 2024

Subscribe to CPSA news

A house with a dark roof absorbs heat, which may cost $700 more per year to keep cool according to recent research.

If you’ve ever walked down the road on a hot day, you know how much the dark-coloured asphalt can heat up compared to the lighter-coloured footpath. This is because dark colours absorb more light, and therefore more heat, than light colours.

The same is true for our houses. A dark roof heats up much more than a light roof: up to 30 degrees more.

According to recent research, this extra heat can mean that some households are paying hundreds of dollars more on their energy bills. The average household electricity bill in New South Wales was $1827 last year. But for a household with a light roof the bill was up to $694 cheaper, because these households needed to use less electricity to keep their homes cool. For a house with solar panels, the added heat from a dark roof can also reduce the efficiency of the photovoltaics and reduce their overall lifespan.

A problem of poor planning

In some parts of Australia, this issue is exacerbated by other aspects of urban planning. As well as having many dark roofed buildings, new housing estates in the outer suburbs of Sydney are often characterised by wide streets, few trees or green spaces and little space between buildings. All of these features increase the amount of dark-coloured hard surfaces that can absorb and radiate heat while also limiting the amount of shade or air flow that could help to cool the neighbourhood.

Households in these neighbourhoods often have to rely on air-conditioning to keep cool during hot weather, but this has the added effect of blowing the hot internal air outside into the narrow spaces between buildings. If numerous houses in the neighbourhood run their AC at the same time, this can increase the heating effect even more.

A few years ago, the NSW Planning Minister proposed a strategy to keep suburbs cooler and reduce household energy bills. The strategy would have banned dark roofs on new developments, added regulations to improve green space and shade, made suburbs more walkable and limited some of the planning decisions that contribute to the urban heat island effect.

Unfortunately, powerful developers lobbied to oppose the strategy, leading the former NSW Government to abandon the plan. The current NSW Government has proposed a similar strategy (albeit one that has fallen short of banning dark roofs outright) before ‘pausing’ the policy until July this year.

No options for renters or low-income homeowners

While those who can afford it can build a home with a light-coloured roof or can repaint or replace their existing dark roof with a lighter colour, the lack of planning regulations leaves renters and lower-income homeowners out in the cold, or more accurately, in the sweltering heat. This means that those who can least afford it will continue paying more on their electricity bills.

Uncomfortable and even dangerous heat levels are already a major problem for renters who have no ability to make structural changes to their homes. But as average temperatures continue to increase, the problem will only get worse unless the Government steps in to improve planning and housing standards across the board. According to a recently released report from Better Renting, this most recent summer saw NSW renters experience median indoor temperatures of 25.2 degrees, with half their time spent in humidity above 65%. Importantly, these figures include homes with fans, air conditioning and other cooling options. This combination of high indoor temperatures and high humidity can not only feel oppressive, it can also have adverse health effects, especially for older people or people with existing health conditions.

Until the Government improves the regulation, these problems are only going to get worse.

For more information please email our media contact at media@cpsa.org.au

Stay up to date with CPSA news and media releases

Our regular email newsletter provides valuable insights and information on topics such as pension entitlements, healthcare, government policies, and more.

  • This field is for validation purposes and should be left unchanged.