This week's cartoon describes white roofs — a low tech fix for our heat absorbing, wasted rooftop space. White paint or tiling can act much like earth's snow covered poles; reflecting the sun’s light and heat as opposed to absorbing it. Research shows that this keeps buildings cooler, reducing the problem of urban heat islands and saving energy (and money). If enough people decided to “paint the town” white, we could counteract global warming simply by increasing the Earth’s total reflective surface. Read through the WorldChanging archives to learn about other ways to utilize our sixth wall by creating green roofs and solar roofs.
Editor's note: This post is part of a series featuring Worldchanging ally Andy Lubershane's original graphics. While many of the issues covered in the comics have been discussed on Worldchanging in the past, we hope that you'll be able to use this new medium in a different way … whether it's in your classroom, on your office wall, or to help explain ideas to friends and family.
Such a simple idea. I have an uninsulated garage that absolutely cooks in the summer. I can only imagine what happens in my attic.
The unintended consequence of the principle of reflecting sunlight, say with the vertical glazing on tall buildings, is that under some conditions you can cook your neighboring buildings, and they end up using the energy that you were conserving...
But if you live in a colder climate (for the time-being, at least), what about the idea that a dark roof absorbs the solar radiation and helps to keep your house warm in the winter? Presumably, this means you'd require less of whatever kind of energy you're using to heat your home....Air-conditioning is not the issue for those of us who live in temperate climates....
I wonder if this solution hasn't been painted with too broad a brush. Whitewash as greenwash? I find it hard to believe that white is the optimal color at all latitudes, in all climes, through all seasons. Has anyone done region-specific modeling on this type of passive construction to balance heat absorption during winter months? Or is the underlying point that good insulation keeps the heat in during cold weather and white paint keeps the heat out during summer?
This doesn't match up very well with the idea of putting solar panels (very dark or black) on roofs. It does however bring up an interesting question. What would be the climate effects of large-scale use of solar panels? As with ecosystems the solutions to environmental problems are complex and multivariate. Suggestions for solutions need to be evaluated with this complexity in mind.
It would be more effective if the all Local, County, State & Federal Highway Department and All WALMART & Big Box Stores paint their black asphalt parking lots and roads White.
My father in the mid-1950's and 1960's owned a company called Kool Roof in Coral Gables FL because he knew for every dollar spent, you cooled your home more with a white roof than with an air conditioner, the business he left before Kool Roof.
Now one can purchase EnergyStar-certified roof paint that is the top of the line, and I believe, there is a 30% tax credit too.
This is a response to Raymond who presented a concern that solar panels are dark and therefore may add to global warming. This is an interesting paradox that Raymond brings up: Rooftop solar panels, are very dark, yet do NOT contribute to the problem--let me explain.
(Review: White surfaces are light or bright because they are reflecting much more light than they are absorbing. Dark surfaces objects are dark because they are absorbing light into themselves, not letting it bounce back up to your eyes and or into space generally.)
When black or dark surfaces absorb light, that light is USUALLY but not always changed into heat, which is passed on in through convection or radiation. Photovoltaic panels are very clever inventions because they absorb that light energy and do NOT turn it into heat energy, but instead turn it into something else--electricity! Sunlight is not being turned into heat at all, but into something else.
Plants are similar in this--they are relatively dark, but only the dark branches or trunks are warmed by the sun (which may help survival in the winter, and turn some processes on and off according to season). The leaves absorb light into their own energy conversion factories, changing light energy through the process of photosynthesis into stored in chemical bonds that others in the food web use for food energy. Leaves are relatively dark, but do not turn light into heat.
A fully solar-paneled roof then, is really an upgrade or deluxe version of the white-roof approach. It would be nice if we could develop durable PV paneling (or photosynthesizing panels) that could cover or replace the asphalt surfaces in our cities. (Perhaps if this had been featured in the early Star Trek shows, someone would be working on it now--but we don't just now have the luxury of focusing on climate correction approaches that will take decades to get into development.)
I just went outside to feel if the leaves were hot in our 8000' high hot sun. They were cooler by quite a bit than even the white surfaces of my car! I guess "green roofs" (covered with living plants, that is, not painted green) might, like solar paneled roofs, be an upgrade to the white roof as well!
Yup I buy the idea of white roofs for a tropical climate.
Here is one roof which does that and a bit more