Posts Tagged ‘solar reflectance’

The surface of a dark roof can reach 180° on a sunny day. A roof that hot does a lot to the temperature inside the structure, a situation that would be welcome in Minnesota in January but is more likely to occur in Texas in August. The heat is absorbed into the structure where, even with its tendency to rise, will still elevate the inside temperature increasing the need for and cost of air conditioning. That superheated roof will also send some of the heat back out into the surrounding air, creating what are called “heat islands” in densely populated areas. While absorbing the suns heat, a dark surface also absorbs its rays, lowering the earth’s overall solar reflectance (called albedo) and possibly promoting climate change. For those reasons there is a growing movement...(read more)

On Monday while discussing dark roofing materials we mentioned albedo, a word we are sure the majority of non-scientists have never heard of. That may not be the case for long. Here's the deal. Albedo is defined as high solar reflectance, i.e. the earth's capability of bouncing the sun's rays back into the stratosphere. If a surface absorbs all light it looks black and has an albedo of 0; if it is perfectly reflective it looks white and has an albedo of 1. All surfaces, in fact all objects, have an albedo within those two numbers. A new sheet of copy paper has an albedo of 1 while a brick wall or a freshly plowed field has an albedo closer to 0 than to 1. When the rays are absorbed or bounced, so is the accompanying heat from those rays. Thus the many chocolate colored roofs and...(read more)