(playful music) - Oh, hello.

Today, we're in Monument Valley, Arizona.

Today, we're going to be doing a cool experiment.

We're going to be taking a thermal imaging reading of a traditional hogan, a modern hogan, and a house.

Today, we're gonna find out what is the best option.

(bright music) Okay, let's get down to the hogan.

Hogan comes from the word hooghan, which means home.

There's a male hogan and a female hogan, so they come in different shapes and sizes, but we'll focus on the female hogan.

The female hogan is the most popular, and that's the design I'll build for my daughter.

You know a hogan by its single rounded room formed by six, eight, or even a 13-sided structure covered by an earthen exterior.

Inside, right above your heads, you'll see this amazing interlocking timber roof.

And finally, a door that always opens east.

I'm hoping to build my daughter a hogan for her coming into the age ceremony one day.

But with climate change, will this be a comfortable traditional space for my family or a big hot oven?

Back to the experiment.

Today, we're gonna be using in our experiments, this little doohickey right here.

This measures the heat and gives you accurate temperature readings in an image, and it's pretty cool.

Then it shoots it to your phone.

Then this is what we're going to be watching throughout the experiment.

And right now, I'm in Monument Valley, Arizona, and it's pretty hot right now, and windy.

And it's about 100-ish.

And let's go see what we find out.

(playful music) (wind rustling) So, my mother-in-law is struggling with the vacuum.

This may look trippy, but this camera captures infrared radiation emitted by objects and converts it into helpful images.

The warmer the colors, the warmer the temperature.

To demonstrate an example of my car.

On the metal, 87, 86.

(playful music continues) 92.

Wowsers.

110, 130.

All right, let's start with the Rez house.

(imitates dog barking) The exterior right now is kind of cool, the sun hasn't hit it yet, but let's check out inside.

The walls are 80, 79.

So, in the hall, the floor's 68, 80, 71.

It's pretty hot in here.

Okay, let's get a thermal reading of the traditional hogan.

(wind rustling) And walk inside.

Here we go, 93.

Oh man, it's like 69, 68.

It is cooler in here.

It is way cooler in here.

There you go here, outside 108.

And finally, the modern hogan.

Modern hogans are the same overall shape as traditional hogans, but use a mixture of modern and traditional materials.

Whoa, it is really cool in here.

Yeah, and the ground is just really cool.

It absorbs all my heat.

After reviewing the thermal camera's footage, it showed me that the traditional hogan remained 7.5 degrees cooler on average than the modern house.

Right here in this area, you can see the house is losing its cool, like right here on the ceiling.

So, what's the secret?

How can an older design be handling a new problem like climate change?

The good news is I know someone who knows about hogans and climate change.

It's my brainiac little sister.

Help, help me, help me.

Please can you help me, help me please.

I need your help.

Okay, yeah.

Let's go!

(Nizhoni chuckling) - The type of mud, the type of materials that get mixed up in that mud and clay, that provides great insulation, not only from the heat, but also from the cold winters.

- [Steven] That's climbing researcher, PhD student, paint in my rear end, my little sister, Nizhoni Tallas, and she's right.

The floor and the earthen exterior would give hogans a thermal advantage in the desert.

This is because they have something called thermal mass.

Earthen material store energy better than any other material.

At nighttime, when the desert's freezing cold, the hogan's walls emit stored energy into the central space.

Energy moves from warm to cold, that's just physics.

And right about the time the sun comes up, the walls have cooled, the process starts all over again.

But how do you actually build one of these things?

(tongue clucking) (gentle music) There are very few traditional hogans left.

I know one person who is keeping the traditional alive Roberto Nutlouis.

- My grandma always used to say like, "You don't need to be told what to do."

Like you have a mind.

(Roberto speaking in indigenous language) What are the things that need to happen?

And a lot of it was visiting sites that hogans that are existing somewhere in construction and just really studying the architect of it.

It's basically, post and beam.

So, each main bond beam, the main beam for the octagon shape is held up by three logs.

Again, these are also juniper logs.

They traditionally, that's what the hogans were built with.

They only grow in certain ecological areas.

So, just even going looking for them, you have to know where to look and here it takes a lot of logs.

So, when we're collecting and harvesting these logs from the forest, it's selective cutting.

We're not just clear cutting, we're doing our part as as indigenous people, like this is how we managed our forest.

- [Steven] Roberto showed me all the ins and outs of the hogan he was building.

Juniper logs are the key.

Juniper's a dense hardwood.

This helps with the hogan's thermal mass, but more importantly, they naturally resist rot, and that's why they're used for the most important parts of the hogan.

Each wall is supported by three juniper posts.

They are massive logs, over 15 inches in diameter.

They're weighing about 500 pounds.

From there, the wall posts are secured through these large beams.

The roof is a series of interlocking timbers placed in a special pattern so they won't collapse.

The next step is to feel the gaps with clay and bark from the cedar trees.

This creates a special mixture like adobe.

The layers' thickness varies from hogan to hogan, but Roberto's is about two feet thick, tapering to one foot at the top.

After the adobe is placed on the structure, layers of dirt are placed all over, covering it from top to bottom.

I am not going to lie, I was intimidated by the intense technical detail Roberto shared, but then I remembered another thing my little sister said.

- The cultural significance is also a big part and also the stories that are tied to that.

So, I feel like and includes that in the structure itself and how it's built and how many logs it uses, speaks to how we can also adapt and use this form of home.

- [Steven] The culture, something in our community has helped Roberto finds way, like my sister said, "Our songs and stories have small instructions."

Like where to place the hogan's important beams, how to prepare the clay mixture, all the ways life should be within the hogan.

Back home with my family it was all coming together.

My daughter is going to see the effects of climate change.

That's unavoidable.

But thanks to friends, family, and our traditions, she'll not only have a resilient hogan that can beat the heat, but she'll also have kinship with the environment to guide the next generation of Navajos.

(gentle music)