What If Concrete Could Help Cool Our Cities?

I've spent most of my career around construction materials, so it takes something a little unusual to make me stop and think, Wait...concrete can do what?

A company in Spain managed to do exactly that.

PhotoKrete, a Bilbao-based technology company that grew out of European research, is developing a photonic cementitious material designed to do something we normally don't associate with concrete:

Help cool buildings and cities.

Not by running pipes through it.

Not by connecting it to a mechanical system.

And apparently, we haven't reached the point where the concrete needs a software subscription.

It does it passively, using material science and some pretty fascinating physics.

And the more I learned about it, the more I realized this isn't really a story about concrete.

It's a story about whether we need to rethink what we expect our building materials to do.

We Spend a Lot of Energy Fixing a Problem We Help Create

Walk through almost any major city on a hot summer afternoon and you're surrounded by materials that are very good at absorbing heat.

Concrete.

Asphalt.

Masonry.

Roofs.

Building façades.

Sidewalks.

Parking lots.

They absorb solar energy throughout the day and release some of that heat back into the environment. That's one of the contributors to the urban heat-island effect, where dense urban environments can become significantly hotter than surrounding areas.

Then we do something perfectly logical.

We turn up the air conditioning.

The International Energy Agency estimates that global electricity demand for space cooling has grown by about 50% since 2015, reaching roughly 2,900 TWh. Cooling now represents around 10% of annual global electricity consumption and about 30% of peak electricity demand.

That's an enormous amount of electricity devoted to moving heat from somewhere we don't want it.

And depending on how that electricity is generated, cooling demand also produces indirect CO₂ emissions.

Which raises an interesting question:

What if we could reduce how much heat our buildings absorb in the first place?

That's where PhotoKrete gets interesting.

Concrete That Sends Heat...to Space?

I realize that sounds like I skipped a few chapters.

But that's essentially the idea.

PhotoKrete has developed a photonic mortar using a process called passive radiative cooling. The material is engineered to reflect a large portion of incoming solar radiation while also emitting thermal energy through a portion of the infrared spectrum known as the atmospheric window.

That energy can pass through the atmosphere and dissipate outward.

No compressor.

No refrigerant.

No electricity.

The material itself is doing the work.

European research behind the technology reported a cooling effect of about 6°C relative to standard concrete at peak solar radiation, together with a 62% improvement in solar reflectance. Other field testing cited by the Materials Physics Center has reported much larger differences in surface temperature under particular conditions. Those figures aren't interchangeable with reductions in citywide air temperature, so the real-world performance will depend heavily on application, climate and scale.

That's an important distinction.

But even with that caveat, the concept is pretty remarkable.

The Sidewalk Suddenly Has Another Job

This is the part that really interests me from a construction perspective.

For most of construction history, we've asked materials to perform fairly specific jobs.

Concrete provides structure.

Roofing keeps water out.

Insulation slows heat transfer.

Glass lets daylight into a building.

Façades protect the interior environment.

But material science is increasingly blurring those lines.

PhotoKrete's technology is being developed for pavements, roofs and façades. The company is also working with Catalan manufacturer Breinco on a facing brick incorporating the technology into its surface. Pilot projects have been underway in locations including Barcelona, the Canary Islands, Donostia and Vienna.

Now imagine that concept at urban scale.

The sidewalk isn't simply something we walk on.

The roof isn't simply keeping rain out.

The façade isn't simply enclosing the building.

Those surfaces potentially become part of the city's thermal-management system.

That's a very different way of thinking about construction materials.

Maybe Better Cooling Starts Outside the Mechanical Room

When we talk about making buildings more energy efficient, the conversation naturally gravitates toward equipment.

More efficient chillers.

Better heat pumps.

Smarter controls.

More efficient air-conditioning systems.

All of those technologies matter.

But there is another side of the equation that I think deserves more attention:

Reduce the cooling load before asking the mechanical system to handle it.

Shade the building.

Improve the envelope.

Plant trees.

Introduce vegetation.

Use green roofs.

Improve glazing.

Increase appropriate surface reflectance.

Design streets differently.

And potentially use materials that reject rather than store solar heat.

The IEA specifically identifies vegetation, green areas, green roofs and façades, and high-albedo surfaces on walls, streets and sidewalks among the approaches that can reduce urban temperatures and cooling demand.

The most efficient ton of cooling may eventually be the one we never needed to produce.

This Isn't Just About Sustainability

There is an economic argument here too.

Electric grids around the world are being asked to do considerably more.

We're electrifying transportation.

We're electrifying heating.

We're building enormous data centers.

We're adding manufacturing loads.

And at the same time, hotter weather is increasing demand for cooling.

The IEA expects buildings to be the largest contributor to global electricity-demand growth through 2030, with space cooling among the important drivers.

That means reducing cooling loads isn't simply an environmental issue.

It's an infrastructure issue.

If a roof, pavement or façade can reduce heat gain without consuming electricity, the potential benefit isn't limited to that building.

At sufficient scale, passive cooling could potentially help reduce stress during the hottest periods—exactly when electrical grids are often working their hardest.

Suddenly, concrete starts looking a little more interesting.

Of Course, There's a Catch

There always is.

If someone tells me they've invented a construction product with enormous benefits, no compromises and no limitations, that's usually when I start reaching for my wallet—not to buy it, but to make sure it's still there.

PhotoKrete is still an emerging technology.

The company describes its technology as being around TRL 6–7, meaning it has moved well beyond basic laboratory research but is still progressing through demonstration, validation and commercialization.

There are plenty of questions that will matter as technologies like this scale.

How does it perform after 10 or 20 years?

What happens when surfaces become dirty?

How does performance vary between climates?

How does it affect architectural appearance?

What's the installed cost?

How easily can it integrate into existing manufacturing?

How much difference does an individual building make versus an entire neighborhood?

Those aren't criticisms.

They're the questions construction should ask whenever promising laboratory science begins becoming a real product.

And that's what makes this technology worth watching.

Europe Is Becoming an Interesting Construction Laboratory

One reason I've been paying more attention to Spain and Europe is the amount of experimentation happening around building materials.

PhotoKrete itself grew out of the European Horizon 2020 MIRACLE research project involving Spanish research institutions, and the technology has progressed from research into a company pursuing industrial applications.

That's where construction gets exciting for me.

We sometimes think innovation means completely replacing the materials we've used for generations.

Maybe it doesn't.

Maybe some of the biggest opportunities will come from making familiar materials do more.

Concrete that manages heat.

Glass that manages sunlight.

Façades that generate energy.

Materials that store carbon.

Surfaces that interact with their environment instead of simply sitting in it.

We're beginning to move from passive building materials to functional building materials.

That could be a much bigger transition than it initially appears.

A Thought

We've spent decades improving the machines that cool our buildings.

Maybe the next major opportunity is reducing how often we need those machines in the first place.

Trees can help.

Vegetation can help.

Better building envelopes can help.

Urban planning can help.

And perhaps the concrete beneath our feet and the materials covering our buildings can help too.

The future of sustainable construction may not be one breakthrough technology that solves everything.

It may be thousands of small improvements working together so that our buildings—and eventually our cities—require less energy simply to remain comfortable.

And if concrete can help with that?

I'll admit it.

Concrete just became considerably cooler.

Closing Question

If materials could actively help manage heat without consuming energy, should passive cooling performance eventually become something architects and engineers consider when selecting façades, roofing and paving—not just strength, durability, appearance and cost?