6 ms·

Your point clearly has merit in many cases, but paint seems almost the epitome of practicality. Assuming that it could be mass producible at a price similar to

Your point clearly has merit in many cases, but paint seems almost the epitome of practicality. Assuming that it could be mass producible at a price similar to premium house paints I can't see the problem in bringing this to market. And from the article: > In the US, New York has recently coated more than 10 million sq ft of rooftops white. The state of California has already updated building codes to promote cool roofs.

obmelvin 6y ago
> Assuming that it could be mass producible at a price similar to premium house paints I can't see the problem in bringing this to market. Unfortunately, that's the whole point of this little discussion, right? GP is saying how many things like this, yes, seem like they have merit, but at the end of the day can't be produced practically outside of a lab.
kube-system 6y ago
There are a lot of practicality/implementation concerns to paint other than what color it is. Just as many if not more than there are for battery technologies. Does the paint stick to the surface you want to paint, how is it applied, what is the coverage, is it durable, does it repel contaminants, can it withstand the environmental conditions, is it chemically compatible with the surface, it is chemically a concern for the other items/humans/animals that may come in contact with, can it be produced at scale, does it (and it's vehicle for application) meet regulatory standards? etc...
- blacksqr 6y ago
  They used standard acrylic paint manufacture techniques, just substituting barium sulfate for the usually-used white pigment titanium dioxide. So most such questions should be answered simply by looking at previous experience with existing white acrylic paint.
  - DanBC 6y ago
    So, in about 10 years we're going to have yet another source of trillions of particles of microplastic?
    - hulitu 6y ago
      Titanium dioxide and barium sulfate is not plastic. They are anorganic compounds.
      - DanBC 6y ago
        The other ingredient of acrylic paint is an acrylic polymer.
        loonster 6y ago
        That will not increase plastic in the environment unless the new paint is less durable or incentivizes painting previously unpainted surfaces.
- Tempest1981 6y ago
  Other factors include how it ages, w.r.t. thermal emittance (emissivity) and solar reflectance (SRI). See the "3 years" columns here: https://coolroofs.org/directory https://coolroofs.org/directory Many products drop by several % after a few years.
- clairity 6y ago
  one thing i’ve learned from doing little home improvement projects over the past few years is that paint is a 2-part product, primer and topcoat, and neither should be skipped if you want good results. generally speaking, primer sticks and seals while topcoat colors and protects. this isn’t made obvious in any way to the novice, and big box store workers seem as ignorant about it as anyone.
  - mauvehaus 6y ago
    Depending on the application, the primer coats can fulfill a couple other requirements as well: If you want a really smooth topcoat, you usually want to sand past what you can reasonably/economically/effectively do on the substrate. Some primers are formulated to sand nicely to a powder (as opposed to balling up in clumps on the paper). You'll see this spraying higher quality paint grade work. You have to have a decent surface before you prime, but the primer can really smooth it out for the topcoat. If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this. Shellac is also outstanding as a sanding sealer. You can use that in a couple of ways: to fill the pores in the wood so they don't get full of sanding dust (which can be key if you have inlay of strongly contrasting woods), or to stiffen the fibers of softer woods so you can get a better/smoother sanded surface for the next steps in the finishing schedule. Shellac is also often used as a barrier coat between otherwise incompatible finishes or when you have a relatively fragile stain layer. If you're putting an oil based finish over an oil based stain, you run the risk of picking up the stain as you apply the topcoat, especially if you're brushing or wiping the topcoat. Because the solvent in shellac is alcohol, you can pretty freely brush it over oil or water based stains without risking a disaster. And yes, I do use primers other than shellac from time to time if I have a specific need, but dewaxed shellac is compatible with basically everything, so I always have a can around. N.B. I'm not a professional finisher. Don't take my word on any of this; test your prep and finishing schedule on scrap!
    - clairity 6y ago
      > “If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this.” yes, i learned this the hard way, albeit on a simple set of wall shelves as cat stairs that i can easily fix eventually with shellac and another topcoat (when i get around to it).
coding123 6y ago
Actually that last bit there seems to be more important to me than the actual tech here. So without this tech people are painting rooftops white. And I'm guessing that's already like a 90% reflectivity? -- So there's really nothing to wait for if you want to cool your house. Just buy... exterior white paint. If you wanted to wait for this specific product, that's fine, but that's almost like waiting for 26% efficient solar panels instead of ~23% we already have (even though most production panels are 18% - 22%)... And actually this is also one of those things that also helps beat Tesla Solar roof - get a white paint - THEN add bifacial solar panels. So the Tesla roof panels is actually worse for your overall cooling than regular panels now.
- adrian_b 6y ago
  The whole point of the discussed paper and of their patent applications is that normal white paint is not good enough to cool something exposed to solar light. The white-painted object will heat less than when painted in another color, but it will heat anyway. The white paints described in the paper and in the patent applications, which use either barium sulfate or calcium carbonate instead of the normal titanium white pigment, actually cool the painted object, even in strong solar light.

obmelvin 6y ago

> Assuming that it could be mass producible at a price similar to premium house paints I can't see the problem in bringing this to market. Unfortunately, that's the whole point of this little discussion, right? GP is saying how many things like this, yes, seem like they have merit, but at the end of the day can't be produced practically outside of a lab.

kube-system 6y ago

There are a lot of practicality/implementation concerns to paint other than what color it is. Just as many if not more than there are for battery technologies. Does the paint stick to the surface you want to paint, how is it applied, what is the coverage, is it durable, does it repel contaminants, can it withstand the environmental conditions, is it chemically compatible with the surface, it is chemically a concern for the other items/humans/animals that may come in contact with, can it be produced at scale, does it (and it's vehicle for application) meet regulatory standards? etc...

blacksqr 6y ago
They used standard acrylic paint manufacture techniques, just substituting barium sulfate for the usually-used white pigment titanium dioxide. So most such questions should be answered simply by looking at previous experience with existing white acrylic paint.
- DanBC 6y ago
  So, in about 10 years we're going to have yet another source of trillions of particles of microplastic?
  - hulitu 6y ago
    Titanium dioxide and barium sulfate is not plastic. They are anorganic compounds.
    - DanBC 6y ago
      The other ingredient of acrylic paint is an acrylic polymer.
      - loonster 6y ago
        That will not increase plastic in the environment unless the new paint is less durable or incentivizes painting previously unpainted surfaces.
Tempest1981 6y ago
Other factors include how it ages, w.r.t. thermal emittance (emissivity) and solar reflectance (SRI). See the "3 years" columns here: https://coolroofs.org/directory https://coolroofs.org/directory Many products drop by several % after a few years.
clairity 6y ago
one thing i’ve learned from doing little home improvement projects over the past few years is that paint is a 2-part product, primer and topcoat, and neither should be skipped if you want good results. generally speaking, primer sticks and seals while topcoat colors and protects. this isn’t made obvious in any way to the novice, and big box store workers seem as ignorant about it as anyone.
- mauvehaus 6y ago
  Depending on the application, the primer coats can fulfill a couple other requirements as well: If you want a really smooth topcoat, you usually want to sand past what you can reasonably/economically/effectively do on the substrate. Some primers are formulated to sand nicely to a powder (as opposed to balling up in clumps on the paper). You'll see this spraying higher quality paint grade work. You have to have a decent surface before you prime, but the primer can really smooth it out for the topcoat. If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this. Shellac is also outstanding as a sanding sealer. You can use that in a couple of ways: to fill the pores in the wood so they don't get full of sanding dust (which can be key if you have inlay of strongly contrasting woods), or to stiffen the fibers of softer woods so you can get a better/smoother sanded surface for the next steps in the finishing schedule. Shellac is also often used as a barrier coat between otherwise incompatible finishes or when you have a relatively fragile stain layer. If you're putting an oil based finish over an oil based stain, you run the risk of picking up the stain as you apply the topcoat, especially if you're brushing or wiping the topcoat. Because the solvent in shellac is alcohol, you can pretty freely brush it over oil or water based stains without risking a disaster. And yes, I do use primers other than shellac from time to time if I have a specific need, but dewaxed shellac is compatible with basically everything, so I always have a can around. N.B. I'm not a professional finisher. Don't take my word on any of this; test your prep and finishing schedule on scrap!
  - clairity 6y ago
    > “If you're finishing pine with knots in it, you'll want a primer that will seal the knots, otherwise the pitch will eventually bleed through and discolor the topcoat. Shellac excels at this.” yes, i learned this the hard way, albeit on a simple set of wall shelves as cat stairs that i can easily fix eventually with shellac and another topcoat (when i get around to it).

coding123 6y ago

Actually that last bit there seems to be more important to me than the actual tech here. So without this tech people are painting rooftops white. And I'm guessing that's already like a 90% reflectivity? -- So there's really nothing to wait for if you want to cool your house. Just buy... exterior white paint. If you wanted to wait for this specific product, that's fine, but that's almost like waiting for 26% efficient solar panels instead of ~23% we already have (even though most production panels are 18% - 22%)... And actually this is also one of those things that also helps beat Tesla Solar roof - get a white paint - THEN add bifacial solar panels. So the Tesla roof panels is actually worse for your overall cooling than regular panels now.

adrian_b 6y ago
The whole point of the discussed paper and of their patent applications is that normal white paint is not good enough to cool something exposed to solar light. The white-painted object will heat less than when painted in another color, but it will heat anyway. The white paints described in the paper and in the patent applications, which use either barium sulfate or calcium carbonate instead of the normal titanium white pigment, actually cool the painted object, even in strong solar light.