Our cooling has officially been shut off.

- I'm so hot. - I'm making an off-grid fridge.

It's going to be complicated, possibly amazing...

- Moment of truth. - ...or a huge fail.

Snug as a button.

Mitchell: And I'm gonna cool our bunky with paint.

But this isn't your grandparents' white paint. It's high tech stuff.

Okay, we've got 53 degrees Celsius.

Where's Greg? He's better at the manual labor.

- Oh! - That's actually cool air.

Greg: Can we really cool our planet

with cheap and easy technologies?

- ( groans ) - ( stammers )

No!

Mitchell and Greg: This is "Shut It Off ASAP."

Mitchell: The world is warming, and that excess heat

is causing frequent wildfires, droughts, crop failures,

optimized conditions for disease vectors,

thermal-induced pollution-- the list goes on.

Unfortunately, we don't have a choice.

We need to keep ourselves cool. And that is a problem.

The cooling industry is responsible

for around 10% of carbon emissions,

which is around three times as much as shipping

and aviation combined.

So we have two universal, potentially sustainable

off-grid cooling experiments we want to try.

So there's been a trend in roofs in particular

to think about the color they actually are,

and to figure out how much light and heat they are actually absorbing.

So I decided I'm going to find the whitest paint I can

and paint the entire roof white

to see if we can get a big temperature drop inside

and ultimately cool ourselves down.

White paint has been used to cool buildings

for thousands of years across the Mediterranean,

the Middle East, and parts of Africa.

People have utilized white materials

to reflect the heat of the sun away from their homes.

These white structures, although picturesque

and quaint in the modern era, serve a practical purpose.

I actually spoke with the creator of the whitest paint ever,

which is able to reflect 98% of light,

including UV light, that we can't even see.

Professor, thank you so much

for taking the time to chat today

- about white paint in particular. - It's my pleasure.

We used a few different sort of innovations

that we came up with in seven years.

It's a long journey.

Sunlight has many different wavelengths.

We eventually found that using different particle sizes will help you.

Each particle size can scatter one wavelength.

If you use them all together,

they reflect all the wavelengths well.

So, do you think that there is

a long-term practical application

with cooling cities and potentially helping

against climate change and global warming?

We did an interesting analysis that you just need 1%

of the Earth's surface covered with white paint.

Then that is enough to cool the Earth down back by 1 degree,

and restore our climate hopefully.

That's wild. That's amazing.

Our ice caps naturally reflect incoming solar radiation,

which moderates our climate.

But as the Earth warms and they melt,

the effect is hugely reduced, which warms the Earth further.

Painting the top of buildings, roadways, and even cars

can make up for this and help fight climate change.

I'm gonna be focusing on cooling our food.

I'm gonna be making an off-grid fridge.

I'll be putting it underground, under the soil,

for some geothermal cooling aspects.

We're also going to be having some evaporative cooling aspects,

which will be part of this fridge

which is gonna be using Peltier modules,

which require electricity and fans,

which will be powered by solar panels

in order to create this underground fridge.

- I have so many questions. - They'll be answered in the video. Keep going.

- Okay. - Greg: Oh, there we go.

The complexity of my build means I need help

from Paul, our master builder.

I not only need his power tool skills,

but I also need his muscles.

My fridge has three parts.

There are the Peltier modules.

They need electricity, so we are powering them

using solar panels.

The Peltier models help to take heat away

from inside the cooler and disperse it.

Our evaporative cooling device

cools the outside of the Peltier modules

to maximize their efficiency.

And, lastly, for some geothermal cooling,

we're burying the cooling box and evaporative cooling device

in the ground to keep it colder

and its temperature stable.

More about that later.

Oh, God, I'm so deep in the hole.

Psych! Okay.

So, if you're wondering why I'm digging this hole,

it's 'cause I'm trying to teach you all

how to bury a body. I kid.

So we're digging this hole to put the cooler in,

and it's actually gonna help it keep cold,

because the Earth has so much more mass,

and so essentially it's a lot harder for the Earth to lose heat.

So we're just trying to take advantage

of those geological properties

in order to keep our cooler cool.

Mitchell: With the temperature above 35 degrees Celsius,

sleeping in the bunky has become unbearable.

It's way too hot, so I'm hoping that using a bit of science

will help me cool the place down.

It's time to paint. I've got my security harness.

We've got our scaffolding, and I've got, you know, my coverage and booties

to make sure I don't get any paint all over me.

The temperature right now-- I'm gonna check it--

is at 53 degrees Celsius, so more than halfway to boiling.

Okay, let's explore what makes white paint so special.

So, why is it that different colors

are better at reflecting light?

Whenever you look around you and see something colorful,

you're actually seeing the spectrum of visible light

that the object is not absorbing.

Plants, for example, appear green

because they mostly absorb the blue and red spectrum

and not green light, which is then bounced

off the plant and hits your eye.

When something appears white, that actually means

that every color is bouncing back to your eye,

because, like a prism that splits white light into a rainbow,

white is actually all of the colors combined.

And it's the material or chemical makeup on an object

that defines how light will interact with it.

For example, our paint contains titanium dioxide in it,

which reflects around 80 to 90% of light,

ultimately making it appear white.

All right, first part is always the scariest.

Ooh-la-la!

Okay, that's very white. That's awesome.

This is easy.

Now I just have to be careful I don't step backwards and die.

Greg: The next step in my build

is the insulated box for the fridge,

and it's something I'm not looking forward to.

First, we have to glue this foam insulation,

before we build the exterior of our cooler,

but it is a separate AsapScience episode

about the physiology of why touching foam insulation

literally gives me the heebie-jeebies

and scream and salivate and freak out, so...

I think you should just do it. Or I'll do it!

I'm strong. Okay.

Aah! I hate it. I don't know, please.

Oh-kay. I know I seem insane, but I'm not kidding.

Oh, God, oh, God.

Ho! ( imitating squirting sound )

So skilled, so skilled.

You could do this at home with a normal cooler

that you just bought from a store,

but we've got Paul here.

Go deeper. Press, press, press.

( imitates drill whirring ) Okay, good, good.

- Oh, God. - Oh.

- No. - Oh, my God.

I was like, "Oh, and I'm getting sued."

Where's Greg? He's better at the manual labor.

Mitch is literally watching paint dry, which is very practical,

but not nearly as complex as me trying to make an off-grid fridge.

But it shows you how cool it is

to just paint roofs white.

Like, we can all do that.

Whoo.

It's hot.

Greg: We are currently in an awful heat wave,

so we want to figure out how to cool

our bodies down right now.

If your core body temperature goes above 38.3 degrees Celsius,

you not only risk heat stroke,

but literally denaturing the proteins in your cells.

So the military has developed a couple techniques

to cool yourself down efficiently.

One in particular is called the Arm Emersion Cooling System.

Because your hands and feet have more surface area on them,

you want to focus on those.

If you can put your hands, up to your elbows,

in cold water, in particular, though,

10 degrees Celsius is the optimum,

you can cool your core temperature down

by one degree Celsius.

- Does it feel good? - It's beautiful.

It's refreshing, it's great.

Okay, you may have heard that having a hot soup

on a hot day can cool you down, and this is true,

but only under specific circumstances.

This all has to do with sweating.

You see, the evaporation of water off of your body cools you down,

so eating something hot actually causes you to sweat.

But it's important that it's a dry day and it's not too humid,

and it's important that you also have some skin exposed,

and preferably, maybe, you're in the shade.

Also, there's receptors in your mouth,

the TRPV1 receptor,

which tells your brain, "Oh, my goodness, it's hot. Time to sweat."

And you can trigger those even with hot sauce.

So if you add that to your soup, even just to a cold soup,

you can trigger those receptors, cause your body to sweat,

and cool you down on a hot day.

Mm, warm soup. Refreshing.

Why does sweating have a cooling effect?

The answer is evaporative cooling--

turning a liquid such as sweat

from its liquid state into a gas requires energy.

This energy is taken from our body, or sweat, in the form of heat.

The resulting heat transfer leads to the desired cooling effect of sweating.

For sweating to ideally cool you down,

you need skin exposed to the air that isn't too humid,

you need to be hydrated,

and a shady, windy spot is ideal.

Wind increases the effect of evaporative cooling,

which you may have experienced

after leaving a swimming pool on a windy day.

You'll feel extra cool when wet in the wind.

This is because the wind increases the evaporation rate

of the liquid water from you skin's surface

and accelerates the amount that's being

converted to vapor, thus cooling your body.

( thunder )

'Tis absolutely raining. Cats and dogs, as they say.

I'm very happy that we moved away from the bunky to do this electrical circuitry.

So what we're about to do right now is create

a thermoelectric cooling effect.

We're essentially building a fridge,

but using a really interesting scientific principle.

First step is getting these components onto the box.

This is my favorite part, as someone who considers themselves fashionable.

It's the glasses. Okay.

I'm cutting holes for these things called Peltier modules,

which are made of semiconductors.

Snug as a button. Is that even a saying?

The heat sink is gonna be on this side of the Peltier module,

and the cooler side's gonna be over here.

So because this one's gonna get hot,