passive cooling

glass tower

The most sustainable energy is not renewable.

September 13, 2026 — Leave a comment

It’s the energy your building never needs.

A few years back I interviewed an architect for my podcast. He spent an hour on something that should be obvious and somehow isn’t anymore, a building can heat and cool itself just by facing the right way.

I haven’t stopped thinking about it since.

We build homes that ignore where the sun rises, block the wind, and wrap them in glass that lets the sun in all day with no way to let the heat back out. Then we spend fifty years paying to undo it. Air conditioning in summer and heating in winter have both become so normal we forgot they’re solving a problem the building created for itself.

That energy has to come from somewhere, coal, gas, nuclear. Nuclear seemed like the cleanest way to produce electricity until the heat started warming the rivers it depends on. In France, several plants had to cut output during heatwaves this year because the river water was too warm to cool the reactors properly. Grids buckle under demand spikes exactly when everyone switches their AC on at once. The machine we built to save us from bad design turns out to have its own limits too, and those limits are only going to show up more often as summers get worse.

None of this is abstract for the people paying for it. In Albi, a 36 year old named Pauline Paredes describes her own apartment as a kettle after weeks of 40 degree heat, and says flatly she has to be out of it before next summer. She’s one of hundreds of people a French outlet interviewed this year alone about heat pushing them out of the places they live.

A geographer in Lyon estimates around 100000 people already leave French cities every year for the outskirts and the countryside because of it, and expects that number to double as the heatwaves keep stacking up.

Winter runs the same script in reverse. More than five million French households live in fuel poverty, a third of the country couldn’t properly heat their home this past winter, and three out of four households are now rationing their heating just to keep the bill within reach. None of that is a footnote to a design conversation. It’s what happens when a building depends entirely on a machine, and the machine gets too expensive to run or the grid buckles at the exact moment everyone needs it most.

Passive solar design isn’t futuristic. It’s ancient. For most of human history people built with the climate instead of against it, thick walls, shaded courtyards, windows placed on purpose, trees that dropped their leaves right when you needed the sun back. None of that was decoration.

We gave that up the moment cheap energy got easier than good design.

The shift has a start date. In 1952 the United Nations Secretariat went up in Manhattan as the first tower wrapped entirely in glass and cooled entirely by machine, followed a few years later by Lever House a few blocks down. Neither building was designed around the sun. Both were designed to look like the future, and cheap postwar energy is the only reason either one got away with it. Every glass tower built since has copied that template. Offices cooled that way now run about 60% higher in carbon emissions than ones that use natural or mechanical ventilation properly. We didn’t inherit bad buildings. We inherited a look, and we’re still paying the electric bill for it.

Every architect knows where the sun rises and sets. Yet, somehow most buildings are still designed like it doesn’t matter. In the northern hemisphere, your longest wall generally wants to face south. That one decision decides how much free heat you get in winter and how easily you can block it in summer, before a single brick goes down.

In winter the sun sits low. It travels under the roof overhang and warms the floor and the walls, which quietly hold onto that heat all day. Six months later the same window behaves completely differently. The summer sun sits high, the same overhang blocks it, the room stays bright without turning into an oven. Nothing moved. Nothing plugged in. The only technology was geometry.

Get the geometry wrong and inefficient turns into dangerous. London’s 20 Fenchurch Street tower, nicknamed the Walkie Talkie, curves its south face inward like a satellite dish. In 2013 that curve did exactly what a concave mirror does, it focused the sun into a single point on the street below. The hot spot passed 90 degrees Celsius. It melted panels on a parked Jaguar, warped a bike saddle, and set a doormat on fire outside a barbershop. The developers ended up bolting a permanent sunshade onto the building afterward, aluminum fins running from the third floor to the thirty fourth, a fix that cost millions of pounds because nobody modeled where the sun would actually land before they built it.

Cooling didn’t start with a compressor. It started with a window across from another window. Cross ventilation works on one idea, put openings on opposite sides of a space so air has somewhere to go. Wind comes in one side, pushes the stale heat out the other, and the building breathes on its own.

Older buildings understood this without needing to be told. Doors lined up with courtyards. Vents sat high to let hot air escape. Floor plans stayed narrow so every room caught moving air. A lot of modern apartments do the opposite, one glass wall and nowhere for heat to go. So we swap airflow for machinery and act surprised when cities burn through electricity every summer.

Thermal mass sounds technical. It’s actually closer to cooking. A cast iron pan stays hot long after it leaves the stove because it holds heat. Stone, brick, and concrete do the same job inside a building, soaking up warmth slowly, holding onto it for hours, letting it go once the temperature drops.

That’s why old stone houses stay cool through a scorching afternoon. The walls delay the heat instead of handing it straight to the room, then let it go outward once night air drops below the temperature of the stone, which is also why throwing every window open after dark was never superstition, just the last step of the same system.

A light building reacts to the weather. A heavy one negotiates with it. The difference is a few degrees you never had to pay for.

Somewhere along the way we split architecture from the landscape around it. That was the mistake. A mature deciduous tree, the kind that drops its leaves every winter, is one of the oldest climate technologies we have. In summer its leaves catch the sun before it reaches your roof. In winter those same leaves drop and let the light back in, right when you need it.

Compare that to a parking lot, which soaks up heat all day and radiates it back into the block long after dark. Trees do the opposite, they cool the air around them while they’re at it. During a heatwave, tree canopy runs eight to twelve degrees Celsius cooler than bare pavement, and a shaded sidewalk can feel up to 14 degrees cooler than one with nothing overhead. We keep shopping for smarter cooling systems while we cut down the oldest and most efficient ones.

None of this needs a backyard. A fifteen story block can face the right way and breathe on two sides just as easily as a bungalow, because the physics doesn’t care how many units are stacked on it. Sprawl is the real opposite of passive design, not density. Sprawl is what happens when a city spreads instead of stacks, and it only survives on a car in the driveway and a compressor on the wall.

People ask if insulation is the most important feature of an efficient building. Insulation matters, but it comes after the fundamentals. A well designed passive building stacks orientation, shading, ventilation, thermal mass, and insulation into one system where each part is quietly doing the others’ job too. Orientation catches the winter light. Overhangs block the summer sun. Trees add seasonal shade. Windows catch the wind. Walls bank the day’s heat. Insulation keeps all of it from leaking back out. None of this is new. It’s just been sitting there unused for about a century.

Climate change keeps exposing how badly we build. Our answer is always the same, a bigger unit, a stronger system, more electricity. We rarely ask if the building was ever designed with any of this in mind to begin with. Passive design offers something else, comfort you get from understanding a place instead of comfort you buy every month. Latitude, wind, trees, sunlight, seasons.

A building shouldn’t have to fight the place it’s standing in every single day, and for most of human history none of them did. Architecture was an extension of the land before it became a product line.

Pauline Paredes shouldn’t have to leave Albi to stop living in a kettle. The five million households rationing their own heat this winter shouldn’t have to choose between warmth and food. None of that is the weather’s fault alone. It’s the bill for a hundred years of buildings that were never asked to do their share of the work.

The most sustainable energy was never going to be the one we invent next. It was always the one we stopped needing the day we designed the building right the first time. We just built our way out of remembering that, one glass tower at a time.

Teekay

ac unit

The end of outside

August 27, 2026 — Leave a comment

The greatest tragedy of global warming is not that the planet is getting hotter.

It’s that humanity is slowly abandoning the outdoors.

We’re sleepwalking into an indoor civilization where the sun becomes something we look at through glass, fresh air is replaced by recycled air, and daily life happens inside sealed boxes connected by roads built for machines instead of people.

We call this adaptation.

I call it surrender.

For most of human history, we survived heat and cold without turning the atmosphere into an appliance. Homes had thick walls and were oriented for natural cooling and heating. Streets were narrow and shaded. Courtyards created airflow. Trees cooled entire neighborhoods.

In the Sonoran desert, on the Arabian peninsula, across the Arctic circle, people lived for thousands of years in the harshest climates on earth, not by avoiding them but by designing for them. Architecture responded to climate because it had to.

Then something changed. Construction stopped answering to climate and started answering to speed and margin. Cheap materials, fast timelines, glass towers that look identical from Dubai to Shanghai to New York City.

This happens under different economic systems in different ways, but under capitalism specifically, the incentive is sharpest and the scale is biggest. We paved cities with concrete, cut down trees, covered skylines with heat trapping glass, and filled streets with cars that turn neighborhoods into furnaces.

Instead of questioning the design, we invented a product to survive it. Every summer gets hotter. Every building gets another compressor. Every apartment becomes another sealed container.

The machine that promises relief quietly becomes part of the world that made relief necessary.

That machine is air conditioning, and naming it here isn’t a knock against it. In 1936, before home AC existed anywhere in the US, a heat wave killed close to five thousand people across the country, most of them in homes with no insulation, no shade, no relief.

That death toll wasn’t inevitable and it wasn’t just bad luck. It happened in the middle of the Dust Bowl, and the Dust Bowl was manufactured. Farmers had stripped the deep rooted native prairie grass, the kind that held moisture and cooled the ground through the plants themselves, and replaced it with shallow rooted wheat grown for profit.

When the drought came, there was nothing left to hold the land together and nothing left to cool it. Indigenous communities had farmed those same plains for centuries without triggering that collapse. The 1936 death toll wasn’t proof that hot places are hostile to humans. It was proof of what happens when land and housing get built for yield instead of for the climate they sit in.

AC didn’t create that problem. It arrived as a patch for a problem that profit driven land use and profit driven construction had manufactured, and it’s remained a patch ever since, papering over bad design instead of fixing it.

That’s the honest version of the argument. Not that AC invented the crisis, but that we reached for the machine instead of reaching for the wall thickness, the window placement, the shade, the airflow that would have made the machine unnecessary in the first place.

Spend time in many hot, humid cities today and you notice something unsettling. The day disappears. Life retreats to dawn and returns after sunset.

Office workers leave an air conditioned apartment, enter an elevator, board an air conditioned train, spend nine hours in an air conditioned office or mall, and return home after dark. Entire days pass without sunlight touching their skin.

Not because they hate nature. Because the city has made nature hostile.

Outside is heat that exhausts you within minutes. Humidity that clings to your lungs. Mosquitoes thriving in a warming climate, carrying diseases that turn an open window into a calculation of risk. Pollution hanging over traffic. The safest option becomes staying inside.

Home stops being shelter. It becomes life support.

The cost is much larger than vitamin D deficiency, though that’s where it starts. Less sun on skin means less vitamin D produced, and vitamin D deficiency is tied to low energy, low mood, and a weaker immune system, which is why people who spend their days sealed away from sunlight tend to get sick more often, not less.

Our bodies evolved with morning light, changing temperatures, wind on our skin, fresh moving air. Circadian rhythms sync to dawn, not to LED panels, and when that sync breaks down, sleep breaks down with it, and disrupted sleep drags hormonal cycles, mood, and energy down with it.

Recycled indoor air adds another layer on top. Research on indoor air quality has linked poor ventilation and recirculated air to worse asthma symptoms and higher rates of respiratory illness, especially in buildings that trade fresh air exchange for sealed, climate controlled comfort.

Even our eyeballs are stretching out of shape. Children who spend most of their days indoors under artificial light are developing myopia at rates that have doubled in some countries in a generation, while the ones who spend two hours a day outdoors are far less likely to need glasses at all.

There’s a crueler twist hiding underneath all of it. Studies comparing people who live in constantly air conditioned spaces to people who live with natural ventilation find that the AC group’s bodies lose the ability to handle heat at all, weaker sweat response, less tolerance, more discomfort at the same temperature a naturally ventilated body handles with ease.

The machine doesn’t just fail to fix our relationship with heat, it erodes our own built in defenses against it, so we need the machine more, not less, the longer we rely on it.

And a life spent moving between sealed rooms is a life spent sitting down. Outdoor space invites movement in a way four walls never will, and the sedentary indoor hours we’ve traded for it are independently linked to weight gain and rising obesity, on top of anything diet explains.

Sleep, mood, hormonal cycles, the air in our lungs, the shape of our eyeballs, our own tolerance for the climate we live in, our own bodies at rest, all bent out of shape by a relationship with the natural world that modern urban life steadily erases.

We’ve normalized breathing recycled air more often than fresh air. That should horrify us.

The cruelest part is the loop that follows. The hotter cities become, the more air conditioners we install. The more compressors run, the more waste heat gets dumped straight back into the streets.

Research on Phoenix Arizona has found that AC waste heat alone pushes nighttime outdoor temperatures up by more than one degree Celsius, right when the heat should be breaking. Elsewhere, modeling done on a city like Paris found that if every building ran AC to hold a comfortable indoor temperature, the waste heat could raise the temperature by up to three and a half degrees Celsius.

The same mechanism behind the Dust Bowl I mentioned earlier is still running quietly in American suburbs today. Grass and trees cool the air through evapotranspiration, water moving up through roots and out through leaves. Strip that away for pavement and clean-cut lawns and you lose all the moisture. The ground stops cooling itself the way it used to, so the heat just builds and kills the remaining grass.

Singapore has more air conditioners per capita than anywhere else in Southeast Asia, and it has also spent years planting rooftop gardens, vertical greenery, and tree canopy to bring outdoor temperatures down.

The greenery helps, but the heat from all those compressors doesn’t disappear just because there are more trees to stand under. As long as the AC stays, the waste heat stays with it. Greening a city while leaving mechanical cooling untouched isn’t the answer, it’s proof that the answer has to include using less of the machine, not just planting around it.

This is capitalism distilled into a single object.

Create the crisis. Sell the adaptation. Repeat.

The future should not be millions of homes humming behind permanently closed windows.

It should be cities dense with trees instead of parking lots. Buildings designed for cross ventilation, thermal mass, and passive solar heating and cooling instead of sealed glass that needs a machine to survive its own design. Public spaces that invite people outdoors instead of shopping malls that replace them. Fewer cars. Less concrete. More shade. More wind. More life.

We don’t need to get better at hiding from the climate. We need to build a world where hiding is no longer necessary, and stop mistaking climate control for control over the climate.

Global warming is not only melting glaciers. It’s melting the very idea of outside. If we accept air conditioned isolation as the endpoint of civilization, we’ve accepted far more than a hotter planet.

We’ve accepted the disappearance of human life beneath the open sky.

Teekay