48 ms·

White roofs are great -- just like snow, the high albedo means a lot of the heat energy is reflected not absorbed. But.. the ultra-white paint, on a roof? Perh

White roofs are great -- just like snow, the high albedo means a lot of the heat energy is reflected not absorbed. But.. the ultra-white paint, on a roof? Perhaps it will be ultra-white on the first few days. Rain, pollution, dust, smog, and a myriad of other particulates (esp. in an urban setting) will quickly render it off-white, and bring it on par with existing finishes.

toss1 6y ago
It seems the existing finishes would also degrade along exactly the same curve. Starting at a higher point on the curve might leave this finish, in it's environmentally degraded state, still brighter than the other white finishes when new, and certainly brighter after both are exposed. Also, if this were that big a problem, it seems that solar panels would fail. It seems that rain often counteracts the pollution, dust, & smog items on your list, washing them off.
- cwkoss 6y ago
  Solar panels will drop in effectiveness as they get dusty and dirty. They need to be cleaned periodically.
  - toss1 6y ago
    Of course, and the cleaning interval depends on conditions, sometimes years. Similarly, windows and buildings are also periodically cleaned. I'm not seeing a problem here that supports GP's implication that the new 98% reflective paint is somehow rendered useless vs existing extra-bright ~85% white paint, which already demonstrably works. It seems that the new paint would work better on any cleaning schedule, up to the point where the pollutants fully covered both surfaces. Am I missing something?
- btbuildem 6y ago
  I think it's a cost-benefit balance. Anecdotal, but when you see things bleached by the sun, they're pretty white -- not ultra #FFFFFF white, but pretty white. My roof is done with a modern membrane, which is very light gray in appearance, with tiny white stones embedded in it. I imagine you can take a roof like that (say 80% albedo) vs a high-tech ultra-white (99.9% albedo), and the 80% roof won't degrade in reflectiveness because the sun naturally bleaches things to that level -- but the wear and tear of high-tech roof will bring it down to about the same. Just musing here, no solid evidence to support this.

toss1 6y ago

It seems the existing finishes would also degrade along exactly the same curve. Starting at a higher point on the curve might leave this finish, in it's environmentally degraded state, still brighter than the other white finishes when new, and certainly brighter after both are exposed. Also, if this were that big a problem, it seems that solar panels would fail. It seems that rain often counteracts the pollution, dust, & smog items on your list, washing them off.

cwkoss 6y ago
Solar panels will drop in effectiveness as they get dusty and dirty. They need to be cleaned periodically.
- toss1 6y ago
  Of course, and the cleaning interval depends on conditions, sometimes years. Similarly, windows and buildings are also periodically cleaned. I'm not seeing a problem here that supports GP's implication that the new 98% reflective paint is somehow rendered useless vs existing extra-bright ~85% white paint, which already demonstrably works. It seems that the new paint would work better on any cleaning schedule, up to the point where the pollutants fully covered both surfaces. Am I missing something?
btbuildem 6y ago
I think it's a cost-benefit balance. Anecdotal, but when you see things bleached by the sun, they're pretty white -- not ultra #FFFFFF white, but pretty white. My roof is done with a modern membrane, which is very light gray in appearance, with tiny white stones embedded in it. I imagine you can take a roof like that (say 80% albedo) vs a high-tech ultra-white (99.9% albedo), and the 80% roof won't degrade in reflectiveness because the sun naturally bleaches things to that level -- but the wear and tear of high-tech roof will bring it down to about the same. Just musing here, no solid evidence to support this.