What was the Issue on Dark Roofs all about?
In 2021, former planning minister Rob Stokes announced that the NSW government would ban dark roofs. Banning dark roofs was part of the efforts to achieve more sustainable housing and reach 0 emissions by 2050.
According to a University of New South Wales research funded by the federal government, removing dark roofing might lower Sydney’s average temperature by up to 2.4C. During a heatwave, a light-coloured roof could lower inside temperatures by up to 10 degrees. Professor Mat Santamouris of UNSW’s School of Built Environment said that getting rid of dark roofing would also lower energy use by 30%. In some instances, savings can rise to 40%, according to a comprehensive assessment of 17 building types, from low-lying residential to shopping centres.
Stokes said that ditching dark-coloured roofs could have a significant impact on the urban heat island effect. Along with the ban on dark roofs, Stokes also proposed the Design and Place State Environmental Planning Policy or SEPP. Praised by environmental groups, the Design and Place SEPP was composed of a set of rules which would push developers to build structures that have 0 emissions from day one. It also would require minimum tree cover for houses, electric vehicle charging stations in apartment buildings, and walkable suburbs.
What Happened to these Plans?
While Stokes believed that there are no reasons why dark roofs should not be banned, his successor, Anthony Roberts, does not share the same sentiment. Roberts announced that he would not pursue the Design and Place SEPP. Properly developers criticised the proposal because of its regulatory and cost burdens.
The NSW Department of Planning and Environment clarified that while there is no plan to ban dark roofs, the updated energy efficiency rules proposed to disincentivise them.
To meet the requirements for a passing Building Sustainability Index (Basix) score required for planning approval, the rules would necessitate developers who wanted to construct a home with dark roofing to include improved efficiencies in other aspects of the house to offset its negative impacts. For example, it can incorporate a reflective finish on the roof’s surface or insulation.
The government’s failure to enact a ban on dark roofs, according to Dr Sebastian Pfautsch of Western Sydney University, reflects the ridiculousness of where developers lay their preferences. According to Dr Pfautsch, even if developers insulate the home, the dark roofs will still make the environment hotter. He is not alone in his sentiment.
The director of the Committee for Sydney’s resilience program, Sam Kernaghan, said that removing the dark roof ban is taking a huge step in the wrong direction. He added that requiring light-coloured roof is the easiest step in managing Western Sydney’s problem with extreme heat. While it may not resolve the problem, it is a good start that is easy to do.
What are the disadvantages of dark roofs?
Black roofs are bold and can stand out in a neighbourhood. They are stylish, and they perfectly match contemporary home designs. Many prefer dark-coloured roofs because they can also hide imperfections, such as cracks, uneven surfaces, and misaligned tiles. They also look good and are attractive to home buyers. However, dark roofs come with disadvantages, and these cons do not just affect the homeowners but the environment as well.
Dark roofs absorb more radiant heat from the sun. It makes the house’s interior hotter than a house with a light-coloured roof. This is because it is a poor reflector of sunlight. It absorbs heat instead of reflecting them off. The extra heat will force the homeowner to use his AC units more, resulting in higher energy consumption. This means an increased carbon footprint for the household.
Imagine several houses with dark roofs using their AC systems more during hot summer days. Meanwhile, collectively, the increase in aircon use can contribute to the heat island effect, making the community and environment even hotter. Dark shingles can also get damaged due to their high temperatures. The extra heat it stores can cause it to break down sooner than light-coloured shingles.
What is the Urban Heat Island Effect?
The phenomenon known as the urban heat island effect affects many cities worldwide. The effect refers to the fact that metropolitan regions are noticeably warmer than rural ones; estimates range from 1oC to 13oC. Land modification causes it because developed regions have more hard surfaces that both absorb and radiate heat. They also tend to have a less green cover.
Previous studies have revealed that the density and colour of building materials are important factors in explaining why the temperature difference between urban and rural locations is frequently bigger at night. Roofs stay cooler when they are made of materials that can reflect a significant amount of solar radiation rather than absorb it. The reflectance property of roofs is known as albedo. Surfaces with darker colours have lower albedo values and absorb more solar radiation than surfaces with lighter colours.
What are environmentally friendly roof options?
The ability of the material to radiate heat, or its thermal emissivity, is just as important for cooling as how well it reflects sunlight. For instance, metal has low emissivity and does not easily release heat that it absorbs. Therefore, they are not the most ideal in urban areas, even if painted with light colours. Materials such as gravel, membrane, or clay tile are preferred because of their high emissivity. Green roofs are also an option for homeowners who want a more sustainable home. Of course, solar panels can also help homes become more energy efficient.
Experts say the NSW government should stay on its course concerning dark roofs. It needs to show the people that they care about housing quality. It must be clear about the policies they wish to enforce to address climate change and achieve its net zero target for 2050.
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