Cool Roofs Might Increase Air Pollution
Approximately 35 years ago I learned in horticultural chemistry class how plants utilize the energy of sunlight. This process is called Photosynthesis and is an everyday example of Photochemistry, a sub-discipline of chemistry or the study of chemical reactions that proceed with the adsorption of light by atoms or molecules.
Other examples of Photochemistry are the degradation of plastics and the formation of Vitamin D with Sunlight.
Skin aging: caused by 80% of the Sunlight
Over the last half century, it has been well studied that heat and sunlight have a tremendous effect on air quality. Both, and independent from each other, heat and sunlight can transform the atoms and molecules in the air around us into other chemical combinations that are often harmful for human health. The same photochemical transfer occurs also with most other particles and substances in the air and increases the chemical cocktail in the air we breathe substantially.
In a recent study of the Cooperative Institute for Research in Environmental Sciences (CIRES) it was confirmed that at night – without the energy of sunlight – nitrate radicals naturally help cleanse the atmosphere. Acting as a “janitor” of the night sky, the nitrate radical scrubs away air pollutants such as volatile organic compounds that would otherwise form smog and ozone. The cleansing compound only works nightshifts, however, since sunlight destroys the light-sensitive molecule. The study suspects that the street lights in cities reduce this cleansing effect.
It doesn’t take much to understand that Cool Roofs or Reflective Roofs multiply the light energy in the air, reducing not only light-sensitive molecules but also converting most other atoms, molecules and particles in the air into potentially more harmful chemical combinations.
This can be proven by many simple observations:
- Photovoltaic (PV) elements increase their output with higher light intensity because of the energy in the light (more photons from sunlight increase the electromagnetic interaction).
- The human skin reacts on intense sunlight with a photochemical reaction (often ending in skin cancer).
- Sunlight changes the composition of most natural of man-made materials – typically degradation.
- Plants change their appearance when exposed to excessive light – often they die.
- Plants “suffocate” when exposed to sunlight 24/7.
Sunburn on plant leaf.
Nowadays numerous studies (typically sponsored my manufacturers) focus only on the surface temperature making everybody believe that cool roof, or so called reflective roofs, are environmentally friendly because of the lower surface temperature. Isn't it worth to look at the bigger picture of what happens when reflecting sunlight off of roof tops – i.e. polluting the air with additional sunlight? I am not suspecting that they were paid to ignore this dramatic effect but it shows to me that the responsibility of researchers is in some cases is questionable. My countryman Albert Einstein would have said: “Insanity: doing the same thing over and over again and expecting different results.”
"Cool Roofs" or "Fool Roofs"?
Installation of reflective roofs requires additional protection for workers.