3 ms·

- paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum. - thermochromic windows

4gotunameagain 5y ago
> - paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum. Does such thing exist? And, doesn't high emissivity in the IR mean high IR absorption as well ?
- the8472 5y ago
  It's a fairly recent development[0], a few years before that the principle was demonstrated as a special surface coating on smooth surfaces rather than paint. And it's about the IR window[1], which is smaller than the whole IR spectrum. And sunlight delivers most of its energy in visible light and near IR, so there isn't a problem with reflecting the incoming light while radiating away into cold space in the IR window[2]. [0] https://ceramics.org/ceramic-tech-today/materials-innovations/new-reflecting-paint-achieves-full-daytime-sub-ambient-radiative-cooling https://ceramics.org/ceramic-tech-today/materials-innovation... [1] https://en.wikipedia.org/wiki/Infrared_window https://en.wikipedia.org/wiki/Infrared_window [2] https://www.researchgate.net/figure/Illustration-showing-desired-low-absorptivity-over-Solar-Spectrum-relative-to-desired_fig10_326902771 https://www.researchgate.net/figure/Illustration-showing-des...
ekianjo 5y ago
> - paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum. paint is not free and needs replacement every few years. hardly a solution.
- rowanajmarshall 5y ago
  No solution is free and needs no replacement.
- sschueller 5y ago
  The surface finish of walls may also make a difference. Rough vs smooth and something like that doesn't fade as quick as paint itself.
- hutzlibu 5y ago
  So you are looking for a free magic solution? I mean, I like houses made from big stones but it is probably cheaper to paint an existing house, instead of tearing it down and replacing with stonewalls.
  - ekianjo 4y ago
    Probkem is that it does not scale globally if you can only rely on short term efficacy

4gotunameagain 5y ago

> - paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum. Does such thing exist? And, doesn't high emissivity in the IR mean high IR absorption as well ?

the8472 5y ago
It's a fairly recent development[0], a few years before that the principle was demonstrated as a special surface coating on smooth surfaces rather than paint. And it's about the IR window[1], which is smaller than the whole IR spectrum. And sunlight delivers most of its energy in visible light and near IR, so there isn't a problem with reflecting the incoming light while radiating away into cold space in the IR window[2]. [0] https://ceramics.org/ceramic-tech-today/materials-innovations/new-reflecting-paint-achieves-full-daytime-sub-ambient-radiative-cooling https://ceramics.org/ceramic-tech-today/materials-innovation... [1] https://en.wikipedia.org/wiki/Infrared_window https://en.wikipedia.org/wiki/Infrared_window [2] https://www.researchgate.net/figure/Illustration-showing-desired-low-absorptivity-over-Solar-Spectrum-relative-to-desired_fig10_326902771 https://www.researchgate.net/figure/Illustration-showing-des...

ekianjo 5y ago

> - paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum. paint is not free and needs replacement every few years. hardly a solution.

rowanajmarshall 5y ago
No solution is free and needs no replacement.
sschueller 5y ago
The surface finish of walls may also make a difference. Rough vs smooth and something like that doesn't fade as quick as paint itself.
hutzlibu 5y ago
So you are looking for a free magic solution? I mean, I like houses made from big stones but it is probably cheaper to paint an existing house, instead of tearing it down and replacing with stonewalls.
- ekianjo 4y ago
  Probkem is that it does not scale globally if you can only rely on short term efficacy