In a hot country like Australia, you might find your whole family wilting in summer. So how can you cool the interior without using expensive, eco-UNfriendly air conditioners? Painting your roof white is definitely one of the solutions used over time but is there science behind it, or is it an urban legend? It does work, but by how much does it reduce the temperature?
The UN (United Nations) is the unexpected source of the answer. Their former Secretary-General, Ban Ki-moon, reported that reductions of seven degrees can be achieved with the building’s interior temperatures (from a roof material temperature reduction of up to 30 celsius). This is exciting news and if you want more information before booking a Sydney home painting project, read on!
The Science Behind The Figures
These figures were derived from a research project in western India where they certainly know about the heat! Over 3,000 city rooftops were painted white and had a special reflective coating added. This reduces heat absorption and heat transfer while increasing heat reflection, thereby amplifying the cooling benefits.
The US-based Natural Resources Defence Council, overseers of this project, didn’t find a seven-degree interior reduction but rather a five-degree reduction. That reduction is still a huge factor in human comfort levels. A second project only achieved two-degree reductions in interior temperatures, but citizens in both locations are still happy to extend the ‘cool roof’ programs.
An informal, independent project run by 6 homeowners in South Africa found an interior temperature reduction of five degrees in summer when changing from a dark grey roof to a white roof.
The California-based Berkeley Lab did further research and ascertained that a clean white roof will reflect 80% of sunlight, and the roof material will remain about 31°C cooler during peak summer.
Why Do Whole Cities Not Have White Roofs?
A white roof and walls is actually part of traditional architecture in southern European and North African countries, with New York City recently implementing ten million square feet of white rooftops. In addition, California has updated building codes to include cool roofs to promote energy savings of up to 40% (air conditioning costs).
A study in central India, using solar reflective paint, recorded a saving of 303 kWh in peak summer hours. That’s the equivalent of 285 days of energy for one Australian home.
The Berkeley Lab estimates that wide use of reflective roofing could result in a global cooling effect equivalent to a 24 gigaton carbon dioxide offset (the same as stopping the use of 300 million cars for 20 years).
Want to be temperature cool and eco-friendly cool? Book a roof painting project and exterior home painting in Sydney with the SRAP specialists. Our efficient team of experts is only a call away!