Paint it White
The Federal and State governments are poised for action with their energy saving announcements for home owners last week, and not a minute too soon with the temperature tipping the 40s in Sydney and Melbourne in early February.
The intention to do good is evident, but the actions proposed are treating the symptom of the problem rather than the cause. The government will provide home owners with a grant of $ 1,600 to insulate the ceiling. The two types of insulation are ‘bulk insulation’ - which uses trapped pockets of still air within the product as a physical barrier to reduce the flow of heat - or reflective foil insulation – a shiny surface which is placed inside the ceiling adjacent to the exterior roof and which reflects back the heat. In short the insulation is slowing the transmission of heat from the roof into the house or reversing the flow of heat back out through the roof. In both cases it is treating the heat once it has been absorbed by the roof.
I propose that the government recognises the value in not letting the heat into the roof. This can be done by painting the roof white and reflecting the sun’s light, and not absorbing the light as heat. This idea is as old as the white-washed villages of Southern Europe and North Africa.
The Sydney Morning Herald reported last March 31, 2007 that Associate Professor Eric Hu, a thermodynamics expert from Deakin University who is working at the University of Adelaide now, said that while red house roofs absorbed heat from the sun, white ones would bounce at least some unneeded solar energy back into space and "it will never come back". Professor Hashem Akbari, a scientist at the prestigious Lawrence Berkeley National Lab in California, is an advocate for painting roofs white. Dr Akbari works in the Heat Island Group, which recently completed a study of homes in Sacramento that found buildings with lightly coloured, more reflective roofs used up to 40% less energy for cooling than buildings with darker roofs. Dr Akbari was profiled by the environmental reporter David Adam for the Guardian on January 16 this year.
The State of California has required warehouses and other commercial premises with flat roofs to be white since 2005. Groups in several US cities including Houston, Chicago and Salt Lake City are investigating similar strategies.
Dr Akbari says that roofs don’t necessarily need to be white, as super-reflective pigments can reflect increased infrared light by 40% on dark coloured roofs. In Japan the Public Works Research Institute has experimented with paint coatings on asphalt surfaces that reflect 86% of infrared light yet reflect just 23% of visible light, to keep down glare. This would be good news for a factory or warehouse owner in Mascot who wants to save money on cooling without the glare interfering with aircraft landing at the airport. It is also good news for a home owner in Double Bay who wants to paint their terracotta tiled roof to lower the temperature in their attic, without incurring the wrath of Woollahra Council.
Dr Akbari says that a roof does not need to be coated white, as existing dark coloured tiles may be replaced with white or light coloured tiles or other building materials.
It is such a simple idea, as simple as wearing a white shirt on a hot sunny day. It is – I hope – simple enough to be added to the public conversation on reducing energy costs.
Rohan Calvert. 8 February 2009. Director Men In White Painting Service
