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  • Writer's pictureGabrielle Glasson

are light roof colours more energy efficient?

Planning a new roof as part of your renovation or new build? It's not just about looks. When considering the colour of your roof, there are two significant factors to consider:

  • Your energy efficiency and heating / air conditioning bill

  • The impact of your home on the micro-climate of your surrounding area.

The colour of your roof has a major impact on your home's energy efficiency.

For example, the enormously popular, almost-black 'Monument' roof colour absorbs and reflects almost double the heat of the lighter 'Shale Grey' colour. *(1)

It all comes down to the simple fact that darker roofs absorb more heat, making your home warmer, where lighter roofs reflect heat, keeping your home cooler.

While additional insulation can help to reduce the impact of a dark roof, use the same insulation in a light-roofed home and you'll be making significant savings. In fact, a report by the University of Newcastle (6) found you could yield savings of 25-35% by selecting a lighter roof tile compared to dark tiles.

It's equally true that in winter, a dark roof will help keep your home warm and this is a worthy consideration in colder climates where more of the year is spent with heating on than cooling. Homes with lighter roofs may require more heating, coined 'the heating penalty', however, in the temperate climate of Sydney where heat is a major concern, the benefits of lighter roofs outshine.

Additional to the effect of roof colour on your home's internal temperature are the broader impacts of roof colour on surrounding areas.

Darker roofs have been shown to contribute to the 'Urban Heat Island Effect'. This is where outdoor temperatures experienced in urban areas are hotter as a result of the excess of dark coloured and /or heat-absorbing materials such as bitumen, concrete buildings and dark roofs, along with the reduced ratio of vegetation to provide shade. These materials absorb, retain and continue to radiate heat, even after air temperatures cool in the evening.

According to research commissioned by the federal government (2) , street temperatures can increase by up to 4c during a heatwave because of the heat island effect, and a light-coloured roof in western Sydney could reduce the temperature inside the home by 4c on average and up to 10c during a heatwave. (3)

So significant are the differences that the NSW government is making moves to ban dark roofs as part of environmental planning rules. (2) But for now, you may want to go a bit further than just following government standards around roofing and insulation. Prof Andy Pitman, director of the ARC Centre of Excellence for Climate Extremes at UNSW sums it up like this: "Australian buildings are amongst the worst in the world. We are absolutely, unambiguously crap at building houses for optimal energy efficiency." (2)

It's also not just colour that determines the thermal properties of your roof. Technological advances have resulted in paints and surface materials that are able to better reflect and radiate heat compared to another product the exact same colour. This uses ceramic, glass and metal materials with improved heat reflective properties.

So what can you do to improve the heat reflectivity and energy efficiency of your home:

  • Use a light coloured roof

  • Read up on your roofing material and its heat absorption properties and coatings.

  • If you love the look of a dark roof, consider whether you could just use dark gutters and fascia for contrast instead.

  • Spring for the highest quality insulation you can afford.

  • Cover your roof with solar panels. (Note that solar panels may be more efficient on a lighter roof as overheated panels can reduce in efficiency.*(2))

  • Plant tall trees around your home to provide shade to the hard surfaces of your home so there are less heat-absorbing areas.

(1) article written by Perth architect, Sid Thoo, titled "Does roof colour affect the energy efficiency of my house?"

We'd also like to acknowledge Amelia at Undercover Architect for first highlighting this issue and inspiring us to bring you this post.

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