White Roofs Project Update and White Roofs at Auckland EcoDay Festival on 6th March
White Roofs idea warming up
The idea occurred to me three years ago when looking for a way of making a significant reduction in global warming, and other people around the world have also had the same idea and it is warming up and building momentum.
When I suggested the idea three years ago it may have seemed crazy to many, but now the climate has changed, now that there is a background of serious scientific research on the white roofs concept and it has gained credibility. When the opportunity unexpectedly fell into my lap to launch this project last October, I found to my surprise that the Obama administration were taking white roofs seriously and their new Secretary of Energy (a Nobel Prize wining physicist) was now pushing the white roofs idea (over there they call it Cool Roofs) and they had begun implementing it onto Federal buildings. More recently I noticed there is now a Cool Roofs Project over a number of European countries including the UK, Greece, Italy, France, with funding from the European Union and it appears to be making good progress (more about that in the next newsletter). Recently I noticed that APEC commissioned a study into cool roof technologies and the idea seems to have spread there from America.
Cool Roofs projects in the US and EU emphasise reduction on carbon emissions through cooler buildings and reduced carbon emissions through reduced air conditioning, in other words doing good without it hurting your pocket. The White Roofs Project NZ emphasises cooling the planet by reflecting sunlight back into space, with the added benefit of energy savings and cooler buildings, in other words doing good and benefitting at the same time. Each is focusing on different aspects of the same thing, and both have the win-win component necessary for the idea to succeed.
The idea seems to be coming into being much faster than I had expected with the growing interest overseas, and this will help the project here in New Zealand and may mean that the idea is eventually introduced into national and local administration here sooner than I had expected, as well as more people locally painting their roofs white or spreading the word when they see it gives them an immediate action plan by which they can do something themselves about global warming. Since October 2010 I have received emails from Paihia to Otago.
Help wanted at the Auckland EcoDay Festival
We will be having a booth at the EcoDay festival, 6th March, 10am to 4pm. EcoDay festival is in its 10th year and last year attracted over 90 exhibitors and over 5000 visitors. The event is free and organised by EcoMatters Sustainable Living Centre. More details at http://ecoday.org.nz
Help is welcomed for printing of two long colour banners and possibly some brochures, if you are in the printing business. Also a video projector if you have one to loan for that weekend.
Quoting from the EcoDay site:
“EcoDay is Auckland’s premier sustainable living festival and provides visitors with information and inspiration to incorporate green principles and practices into their everyday lives. Now in its ninth year, the event was founded on the principle that while it is important to raise awareness about pressing environmental issues such as climate change, it is equally important to empower people with practical ideas and tools that will motivate them to make lasting changes to reduce their impact on our environment.”
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While you have my support on having white roofs, I wonder why you are not promoting the unpainted corrugated iron roof? You see, Corrugated galvanised iron provides its own protection for many years if left unpainted and untreated in any way. That’s how galvanising works, by interacting with the weathering of rain and sunshine, and producing a patina from the zinc within the metal.
I added two rooms to my house well over thirty years ago, and left the roof unpainted. 34 years have passed and there’s no rust to be seen! Not even around the lead-head steel nails holding the roof down (the more modern screw-bolt system involves galvanised screws which might be even better). I do recommend no painting of roofs, and certainly no ‘etching’ which removes the galvanised protection, not even where the iron sheets lap each other. And, since that leaves a shiny steel surface the reflective quality would surely equal a white-painted surface.
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Unfortunately, bare metal roofing is much worse as a cool roof than white. Although the metal has decent reflectivity, it has low emittance – it still gets hot. Just touch an unpainted galvanised sheet and a white painted one in full sun at mid-day!
There is probably a lot to be said for the energy and other environmental savings in never painting a roof, however. This kind of environmental accounting gets complicated.
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Hi Bruce and George. Thanks to both of you for your comments. An unpainted galvanised (or zincalume) iron roof does have a good reflectivity when it is new, but this drops off over time as it weathers. Unfortunately, like most metals it also has a low emissivity meaning that it cannot re-radiate heat very well, so as it absorbs solar energy from the unreflected portion of the sunlight its temperature goes up as the heat builds up inside it and it is not a cool roof. To give an example, I measured the temperatures of some standard roofing colours on roofing iron in the midday sun last February and measured black at 74 ºC (scalding temperature) while white paint right next to it was 39 ºC (blood temperature). The new unpainted galvanised sample was 63 ºC (too hot to keep your hand on). But after a few years when its reflectivity has dropped off to low values it gets even hotter than this. You can see the results at http://whiteroofs.org.nz/html/other_notes.html
People have commented to me that when they have been painting their galvanised roof they were surprised at how much cooler the iron was after painting, or even during painting when they have come back from lunch and put one hand on the unpainted iron and the other hand on the newly painted iron right next to it.
I suppose how long an unpainted galv roof would last depends to an extent on the local climate. For example if you lived in a dry climate then it would last longer, if you live in a humid warm climate it would corrode more quickly and need replacing earlier, and it is well known that if you live near the sea it will corrode faster due to the salt deposits from the sea air. Since emissions are generated when the roof is manufactured, the lifetime of the roof becomes a factor when calculating the annual emissions cost over the lifetime of the roof. I don’t have the numbers on this or for emissions from paint manufacture, but it is on my “to do” list when I have time.
By comparison, a number of scientific studies have found that a flat white roof reflects enough sunlight back into space to have a cooling effect that cancels the global warming of roughly 10 tonne of carbon dioxide emissions. And if you have air conditioning then you may also have energy savings from reduced air conditioning use which in turn reduces CO2 emissions. A 2010 study into four types of commercial buildings across the USA, looked at overall energy and emissions savings from replacing a dark roof with a white roof (summertime cooling savings minus winter heating penalty equals overall savings) and found that savings were greatest in the warmer zones in the south of the country and that even up in the cooler zones near the Canadian border there were savings in energy and emissions. This study did not also take into account the added benefit of cooling the planet by reflecting sunlight back into space, as that has been covered in some depth in other papers.
Ian
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