4 ms·

One possible solution to keep the buildings and other structures including automobiles cool is to paint them white. Somehow this is not mentioned much in the me

One possible solution to keep the buildings and other structures including automobiles cool is to paint them white. Somehow this is not mentioned much in the media these days.

Panzer04 3y ago
Yep. It seems like the most effective solution in heat islands would be to avoid absorbing the sun's heat in the first place. For perspective, white paint will reflect 80-90% of the sun's energy, while black paint would reflect only 10-20% (other materials - asphalt, 10%, concrete, ~50%, sand, 40% - look up albedo :)). Given sunlight is approximately 1kW/sqm, simply reflecting it back instead of absorbing it seems like it would add up to big savings pretty quickly, and something like white paint is significantly superior to what you'd get with most other finishes.
- crtified 3y ago
  Stupid question incoming: "simply reflecting it back" - back to where? I'm trying to imagine the full journey of that heat energy, and the whole consequences of reflecting it from the ground.
  - kccqzy 3y ago
    Into space.
    - crtified 3y ago
      At what % efficiency does the reflected heat complete its return journey back out through the so-called Kármán line (or other earth-space boundary relevant to thermodynamics) ?
      - Panzer04 3y ago
        Presumably similarly to on the way in - but mostly high in the atmosphere where you, personally, don't care at ground level. Supposedly it's 1.3kW/sqm at the earth's atmosphere, so take 30% off on the way out and you're at 700W out (approx). On a climate level, reflecting more heat out from earth is technically good too, I suppose :).
        crtified 3y ago
        Fascinating indeed to ponder about the climate impact were a particular country(s) to, say, regulate that all roofs must be made white. One report I read [0] found that, in the urban areas under study, 19-25% of surface coverage was roofs. [0] https://www.osti.gov/servlets/purl/935715 https://www.osti.gov/servlets/purl/935715
asciimov 3y ago
It’s a good place to start, but while it helps, it doesn’t solve the problem, and good luck getting HOAs to approve it.

One possible solution to keep the buildings and other structures including automobiles cool is to paint them white. Somehow this is not mentioned much in the media these days.

Panzer04 3y ago

Yep. It seems like the most effective solution in heat islands would be to avoid absorbing the sun's heat in the first place. For perspective, white paint will reflect 80-90% of the sun's energy, while black paint would reflect only 10-20% (other materials - asphalt, 10%, concrete, ~50%, sand, 40% - look up albedo :)). Given sunlight is approximately 1kW/sqm, simply reflecting it back instead of absorbing it seems like it would add up to big savings pretty quickly, and something like white paint is significantly superior to what you'd get with most other finishes.

crtified 3y ago
Stupid question incoming: "simply reflecting it back" - back to where? I'm trying to imagine the full journey of that heat energy, and the whole consequences of reflecting it from the ground.
- kccqzy 3y ago
  Into space.
  - crtified 3y ago
    At what % efficiency does the reflected heat complete its return journey back out through the so-called Kármán line (or other earth-space boundary relevant to thermodynamics) ?
    - Panzer04 3y ago
      Presumably similarly to on the way in - but mostly high in the atmosphere where you, personally, don't care at ground level. Supposedly it's 1.3kW/sqm at the earth's atmosphere, so take 30% off on the way out and you're at 700W out (approx). On a climate level, reflecting more heat out from earth is technically good too, I suppose :).
      - crtified 3y ago
        Fascinating indeed to ponder about the climate impact were a particular country(s) to, say, regulate that all roofs must be made white. One report I read [0] found that, in the urban areas under study, 19-25% of surface coverage was roofs. [0] https://www.osti.gov/servlets/purl/935715 https://www.osti.gov/servlets/purl/935715

asciimov 3y ago

It’s a good place to start, but while it helps, it doesn’t solve the problem, and good luck getting HOAs to approve it.