White Paint reducing AC energy costs

[svetz]

ref: https://www.msn.com/en-us/news/us/s...conditioning/ar-AAOyydl?ocid=msedgdhp&pc=U531

The paint reflects 98.1% of solar radiation while also emitting infrared heat. Because the paint absorbs less heat from the sun than it emits, a surface coated with this paint is cooled below the surrounding temperature without consuming power.

That's a step up from Henry's Tropi-Cool 90% (CRRC).

Don't worry @Supervstech , while it's a great start the ambient temperature and humidity here will be too high IMO to ever do away with AC....
(Although in SC perhaps a windcatcher side business? ; -)

 

[A.Justice]

I just painted my bare aluminum trailer roof with around 10-15mil of elastomeric silicone coating. The internal temps of my trailer used to exceed 120°f, now it hovers around 90° in the direct sun.

My infrared thermometer said the internal roof surface was over 170° in full sun, it would literally burn your fingers, and slowly destroy wire insulation. Now, it's cool to the touch and I haven't seen it go over 95°.

 

[circus]

paint absorbs less heat from the sun than it emits, a surface coated with this paint is cooled below the surrounding temperature without consuming power.

I can see it now. My solar air heaters circulate air past warm black sheet metal hanging in a glazed box. Paint the backside of the sheet metal white then, in the summer, flip the sheet metal so air circulates past the cooled white sheet metal.

 

[Steve_S]

LMAO seriously, so they Discovered that Pure WHITE reflects the spectrum away and as a result is cooler....
Well GOSH DANG IT, Better tell those folks in Mediterranean regions, Spain & other Warm Locales. I bet they didn't know that painting their homes White and having Light Coloured roofs was a smart idea....

Like (New Terms) "Cool Roofs" and "Rainscreen Siding" which have been used for over 2000 years in various regions to beat the Heat & Cold... psst, Vikings used Rainscreen Method in some places, wasn't called that and adopted to their build methods... And of course the Mari of Australia who designed their homes for teh climate which White Man thought was dumb BUT now realized they had it right all along...

 

[svetz]

...Now, it's cool to the touch and I haven't seen it go over 95°.

Same here. If seeing is believing, here are some panels on my Tropi-cool roof, the dark purple is the far cooler rooftop. The heat under the panels is from the heat radiated by the panels baking in the Florida sunshine:

LMAO seriously, so they Discovered that Pure WHITE reflects the spectrum away and as a result is cooler....

I'm surprised you don't see the significance of this and are mocking it.

It's more than being "white" paint. I've seen Ultrabright white roof coatings as low as 70%, all white paints are not equal and why I went with Topi-Cool (see the CRRC data).

What's new is this paint is 98.1% solar reflectance, which is significant. Something painted with it and left in the sun feels cool to the touch.

Let's run some numbers. White Metal roof panels can be under 70%, but let's say 70% as it's more the norm... from the new 98.1%. So, 98.1 - 70 = 28.1%. At 1000 W/m², 1000x.28= 280 W/m². So, that's about as much energy as a 300W panel. Or, if you like BTUs, a 1000 ft² roof is converting solar energy into 88,700 BTUs. If you use an insolation of 5 that's ~37 tons of AC per day (but don't trust my calculator, it hates me).

On top of the reflectance, the paint also has an IR emittance. so it can also shed energy it gains to stay at/near ambient. Assuming this is actually real and ready to go (e.g., doesn't wear off in a week, get stained by leaves) it's big news.

 

[Steve_S]

Below is a chart from a manufacturer of metalroofs.

 

[Supervstech]

Put this up there as well…

 

[A.Justice]

I used BlackJack Elasto-cool from Lowes. I can't find a reflectivity rating anywhere, but it was so bright that when I put a second coat on the trailer, my arms and face were sunburned on the undersides, and it was almost impossible to look at without dark sunglasses.

https://www.lowes.com/pd/BLACK-JACK-Elasto-Kool-1000-3-6-Quart-Elastomeric-Reflective-Roof-Coating-10-Year-Limited-Warranty/3013308

 

[svetz]

Below is a chart from a manufacturer of metalroofs....

The reflectivity of similar-looking colors varies quite a bit, the CRRC data is by vendor/product and independently measured. I know a lot of people pick using color as an aesthetic, me... I just sorted the database and took the topmost that was locally available. I'm totally clueless about color-matching anyway.

Put this up there as well…

Nice! At least these are "real" and have an actual demonstration deployment. I like the idea of a paint with no moving parts more though.

There's a number of ideas, these guys got 13°C below ambient using a thermally insulating polyethylene aerogel.

 

[curiouscarbon]

 

[Batvette]

I just painted my bare aluminum trailer roof with around 10-15mil of elastomeric silicone coating. The internal temps of my trailer used to exceed 120°f, now it hovers around 90° in the direct sun.

My infrared thermometer said the internal roof surface was over 170° in full sun, it would literally burn your fingers, and slowly destroy wire insulation. Now, it's cool to the touch and I haven't seen it go over 95°.

I had heard that white colors only reflect the RGB visible spectrum of solar radiation, but not the UV spectrum which is 50% of the heat potential. Apparantly polished metal was better overall? Anyone know about this?
In your case maybe the thickness of the coating acted as an insulator?

 

[Shale MacGregor]

I've had good results with tropicool, but never measured
ereasured

 

[A.Justice]

There was something weird with his testing conditions. I would have liked to have seen him use real sun, with black asphalt shingles on the roof of the the control house. That bare wood was pretty light colored anyway.

I don't think that those flashlights and lights put out the same "type" (or wavelength, or whatever) of light as the sun either.

My personal experience gave me an entirely different result.

 

[A.Justice]

I had heard that white colors only reflect the RGB visible spectrum of solar radiation, but not the UV spectrum which is 50% of the heat potential. Apparantly polished metal was better overall? Anyone know about this?
In your case maybe the thickness of the coating acted as an insulator?

I don't have any experience with polished metal, but the original roof was scuffed up aluminum, and it got ridiculously hot.

Based on my experience with the paint, I tend to think that it probably reflects substantially more than half of visible and UV light.

 

[svetz]

 

[aenyc]

You keep pinching pennies with white paint, while John Kerry and his ilk use their private jet. Each usage equates to several million human-years of white paint usage.
They are laughing at you!

 

[Checkthisout]

You keep pinching pennies with white paint, while John Kerry and his ilk use their private jet. Each usage equates to several million human-years of white paint usage.
They are laughing at you!

No kidding!

 

[A.Justice]

To be fair, I used my coating for practical purposes, not environmental. I can load and unload my trailer in the direct sun without burning up now, John Kerry be damned.

 

[curiouscarbon]

NightHawkInLight does some good stuff ?