Nothing freshens up a home like a new coat of paint.
But what if that paint could do more than just change your home’s appearance — what
if it could actually make your home much cooler….
Literally?
Well, that’s just the idea behind a new type of Ultra White Paint developed by researchers
at Purdue University.
The paint is officially the whitest substance in the world — so white that it can actually
create a cooling effect on the objects it covers.
So… could the solution to climate change really be as simple… as a fresh coat of
paint?
How exactly does it work?
And… are there any potential downsides?
We thought these questions deserved a deeper dive today on Two Bit Da Vinci
So when we think of paint… we might think of
those old classic Bob Ross videos.
But can paint really go from making happy little clouds and trees to…
literally saving the planet?
To start, let’s talk about visible light, and what gives colors their color.
First of all visible light is only a tiny little part of the entire electromagnetic
radiation spectrum.
Wavelengths here on this spectrum determine the amount of energy the waves carry.
Things like Radio waves, microwaves, and infrared light, have less energy than visible light,
and things like ultraviolet, x-rays, and gamma rays have more.
In the visible light spectrum, each color perceived by the eye is based on the wavelengths
of light reflected by a surface.
For example, if you look at a red t-shirt, you’re seeing a fabric that reflects more
red light, while absorbing other wavelengths.
A material that absorbs all wavelengths of light is seen as black, because very little
light bounces off and hits your eye.
White then, is the opposite, as a white material, is prone to reflect most of the visible light
spectrum, and all those colors mix to be perceived as white.
This is why a white car stays cooler in the sun, because it reflects more of the sun’s
energy than a black car, which absorbs more.
This then is where we start our journey.
Clearly, white paint isn’t new, so what makes this stuff so much more “white”
and does it actually make that much of a difference?
Well, researcher and professor of mechanical engineering at Purdue University Xiulin Ruan
seems to think so.
The paint developed by him and his team has come as the result of over six years of research
— chasing a question that dates back to the 1970s.
Can you use paint to replace air conditioning?
And after all these years of research — the team finally stumbled on a substance that
has officially been deemed the whitest on earth according to the Guinness Book of World
Records.
Looks like Vladimir Putin’s shirtless chest has been dethroned.
But the team’s goal was never to create the whitest substance.
Instead, they were trying to develop a paint that could generate a cooling effect on objects
— in particular, rooftops and buildings.
It just so happens that in order to achieve that, they also inadvertently created an ultra
white substance — since the color is actually achromatic, and reflects and scatters all
the visible wavelengths of light.
Because white objects don’t absorb any light, they are inherently much cooler than other
objects.
The trick was to find a material that could reflect the most light.
After testing over 100 different materials, the team finally landed on a chemical compound
called Barium Sulfate — commonly used to make photo paper and cosmetics appear white.
It turns out, Barium Sulfate has a high electron band gap for low solar absorptance — that’s
the ratio of the radiant energy absorbed by a body to that incident upon it — and phonon
resonance at around 9 μm — which makes it an incredibly suitable material for a phenomenon
called radiative cooling.
We covered this topic in a previous video about SkyCool systems which you should definitely
check out if this kind of stuff interests you.
Basically, as radiation from the Sun hits the Earth, some of it reflects back out into
space through tiny “sky windows.”
This is why your car might have a layer of frost on it in the morning.
Infrared radiation can pass through clear, dry air in a wavelength range somewhere between
8–13 µm.
This helps this radiation in particular to cut through the water vapor and CO2 in our
atmosphere.
Materials with the right reflective capabilities can bounce that radiation right back out into
space and generate a cooling effect even in direct sunlight.
And it turns out, Barium Sulfate possesses those reflective properties.
But it’s not just a high concentration of particles that give Ruan’s paint, it’s
whiteness.
The size of the particles also plays a crucial role.
By adding particles of varying sizes, the paint’s reflective property increases, as
it scatters even more of the light spectrum from the sun — similar
to a shiny, expertly cut gem.
With particles of the right shape and size, the paint can reach
a solar reflectance of over 98%.
Using white paint to reflect heat is nothing new.
It's been a common practice in places like Greece for years.
And in densely populated urban areas like New York, initiatives to paint rooftops white
have been implemented to combat what’s known as the “urban island effect.”
Basically — a “heat island” is when a structure — like a building, road, or
some other form of infrastructure — absorbs and re-emits the sun’s heat at a much higher
rate than the natural landscape, even after the sun goes down.
Obviously, because urban areas have significantly more infrastructure, they are the biggest
culprits of heat islands.
According to the EPA, in the United States, the heat island effect can result in daytime
temperatures in urban areas about 1–7°F higher than temperatures in outlying areas
and nighttime temperatures about 2–5°F higher.
The problem with most commercially available paints, even white reflective paints, only
reflects between 80 ad 90% of sunlight.
And what’s worse, they still absorb a significant amount of heat.
What makes this new ultra white paint so unique is that not only does it reflect over 98%
of the sunlight — it also creates a cooling effect.
Purdue researchers were able to show that their paint can keep surfaces up to 8 degrees
F below their surroundings under direct sunlight during the day, and up to 18 degrees F cooler
at night.
That’s a pretty big temperature gap considering it’s literally nothing more than a coat
of paint!
Not heat pumps.
No working fluids.
No grid energy to power complex machines.
All things that residential and commercial AC units require, and all of which can have
detrimental impacts on the environment.
And again, all AC units do is transfer heat from inside your house to outside, whereas
this ultra white paint literally sends that radiation back out into space!
Sounds pretty… cool… to us!
When field-testing their paint, Ruan and his team covered a 1,000 square meter roof in
their reflective paint.
The result, according to their data, was a cooling power equalling roughly ‘10 kWhs
of electricity or about 34000 BTUs — more powerful than most residential central AC
units which can vary but tend to average about 24,000 BTUs.
Ruan and his team estimate that this could reduce your electricity bill by about $1 per
day, or possibly more just by painting the roof.
By painting both walls and roofs, retails stores could see up to an 11% reduction in
annual energy costs, while single-family homes could see up to an 8% reduction.
But Ruan sees an even greater potential for his paint — actually reducing global temperatures.
According to Purdue researchers, if just 1% of the planet’s surface were covered in
the world’s whitest paint, worldwide temperatures could drop about 1-degree Celsius — which
is about how much the global temp has increased since 1880 according to NASA.
Of course, as with all scientific breakthroughs, there are some who are skeptical about this
new ultra white paint.
Researchers from both the South Coast Air Quality Management District and the Heat Island
Group at Lawrence Berkeley National Laboratory have suggested that ultra-white paint may
actually contribute to the very problems it’s designed to alleviate.
Some of the research indicated that while white paint does indeed cool urban surfaces,
it can actually prevent moisture and energy from traveling upward to form clouds.
Fewer clouds mean that more sunlight ends up hitting the exposed area which could offset
the cooling effect.
Another potential flaw in reflective paint came via observations from air quality scientist
Scott Epstein who observed that winter-time air pollution in rural Utah was worse than
in the summertime due in part because the white snow actually reflects that UV light
back into the atmosphere.
This then triggers a chemical reaction that forms smog and pollutants such as black carbon
— which of course contributes to heating the atmosphere.
Then there’s the more practical drawback that conflicts with the very problem this
tech aims to solve.
In Winter, any stray sunlight that might have warmed your home, well... now is reflected
away.
In turn, this could potentially lead to higher heating costs, especially on cold days, with
good sunshine.
My Mum was right, you really can’t have it all.
So clearly, this is a technology for cooling in climates where hot summers are worse than
cold winters.
Places like the American Southwest immediately come to mind.
As of right now, the research team is looking for a commercial partner to scale up the production
of the paint and hopes to have it available in the market within the next two years.
The team also intends to investigate creating colors other than white, which will still
maintain some reflective properties though obviously not as much.
This could help the product become more commercially viable cause… you know… we don’t want
all our houses to look the same like some dystopian sci-fi novel.
Imagine a future where your home could be coated in reflective paint and outfitted with
reflective solar panels, creating a cooling effect 24 hours a day while consuming virtually
no electricity!
That sounds pretty chill to us!
But what do you think?
Is white paint the way to go for passive cooling?
Do you think the rewards outweigh some of the potential risks?
Sound off in the comments section below!