A Community of Green Bloggers & Activists
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White Roofs and Surfaces Overlooked Key to Reducing Global Warming

"Surprisingly, Californians can do more for reducing climate change by simply reducing waste solar heating produced by structures & pavement than by conserving energy alone - but please, still do that!" writes Dr. Alex Cannara.  Dr. Cannara is a member of the Menlo Green Ribbon Committee and a noted  scientist in the field of renewables.  Dr. Cannara proposes that many of our initiatives are misguided since fundamental science is absent.

White Roof House

According to Dr. Cannara we receive just 0.0000000005 of the Sun's energy output, during daytime. But, 1 hour of that insolation on earth's sunny side is equivalent to all humanity's energy use for a year.  Our planet receives 1300 watts per square meter (1080 watts per square yard) at the top of our atmosphere.  If this measurement is adjusted for day/night and weather, this reduces to about 400 watts delivered to every square yard of pavement, roofing, vehicle and body of water.  This is heat is equal to aiming 3 hair dryers at each 8ft x 8ft section of a roof or pavement. For a home, it typically amounts to 50,000 watts of heat being delivered directly to the air above a home's roof.

Solar Radiation Spectrum, White Roofs

The real solution then is to change the way we absorb this hear.  Dr.  Cannara points out that using solar panels on your roof is not enough.  "Even with solar-electric, present, non-concentrating solar panels only convert about 15% of sunlight into electricity, turning 85% into heating the air, just like dark shingles."  So the low lying fruit that can change this formula is simply lighting or whitening the colors of the roof shingles, paved areas and structures.

White Roofs, White Surfaces, Scientific Proof

The science behind this is solution is also simple.   When a person paints their roof white they are increasing reflectivity (albedo) of the light coming from the sun. Historically, builders have not considered albedo.  Low albedo (dark) surfaces convert visible sunlight to vibrations of their molecules (heat). This is heat is then re-radiated upward as infrared waves, giving it a second chance at being absorbed as greenhouse gas. By painting your roof white your cause this process to be greatly reduced, which in turn reduces the heat and infrared energy produced.  This in turns keeps structures and areas cooler causing less energy to be expended in cooling.   Dr. Cannara believes that,  "local/global warming is needlessly accentuated, at any level of greenhouse-gas concentration. Correcting this has immediate effect & climate benefit."

White Roofs, White Surfaces, Scientific Proof, Menlo Park Examples

The moral of the science is simple.  One can make a bigger contribution to reduced global warming by increasing all your structures' albedo. "If all human structures improved reflectivity by 50%, it would have an effect equal to everyone on earth using no fuels for energy for a year. A year. There is no bigger, more straightforward, or economical contribution each of us can make."  Thank you to Dr. Cannara for his research on this topic and you may contact him at [email protected].