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Instead of relying solely on air conditioning, which often adds to greenhouse gas emissions if run on fossil power, there are a number of passive solar design strategies that work without additional energy:

- Solar chimneys draw cool air in when it’s sunny via pressure differential

- Building orientation along with natural shading from deciduous trees prevent excessive solar insolation heating the building

- Building on top of a thermal slab to provide enough thermal inertia to prevent excessive heat during the day

I wrote more details on this on my blog: https://uplevelgreen.com/passive-solar-cooling-in-hot-humid-...

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Somehow this has been lost over the years. I can especially see this in Zürich Switzerland where new office buildings being built are awful and there seems little thinking about temperature. Everything is managed by complex air systems to move air from one area to the other.

On the other hand you go into a 200+ year old building and you notice it's cool in summer although there is no air conditioning. The building is positioned in such a way that it stays cool for the most of the day, the walls and windows are placed to optimized for this. It's not 100% but if you added a cooling system you would have a perfect setup.

We rely to much on technology to build these ugly boxes instead of also considering the building shape and position itself.

I would assume it's mostly the thicker walls, at least it was this case in Berlin with older buildings staying cool for a long time because it took months to heat the walls. Then those walls were warm in winter and it took months to cool them down (though it didn't work very well in the last very hot summers that were hot early on)

This is still sometimes done. The newest section of the Freie Universität Berlin campus (the “Holzlaube”) was built so that the inside remains comfortable with no A/C and minimal heating. Thick walls, as you said.

I don’t know how applicable architectural cleverness will be in densely populated cities in the developing world that are threatened by global warming. That seems like an impossible situation.

Many parts of the world the outside will be unhabitable :-(

maybe i'm squinting too hard,

but I see this as related to a more general attitude of imposing our will while disregarding what is already there.

"why would we want to position the building according to where it is? specially when there's an alternative of putting it however we like, and then involving a sophisticated air system which will isolate the building from it's environment (which is going to shit anyways) and also, think of all the jobs, the infrastructure, electricity, generators, coal-mining, ac technicians, etc that come with an AC based building! if the building, just by virtue of where it is, can do without all this then the economy will shrink, we cannot have that."

As someone who was in Europe for one of the heatwaves of recent years, and whose appartment was in one of these older buildings designed this ways with thick walls etc., I can attest that this only works up to a point. This design relies on there being cold air for the building to retain. However, in a heatwave it doesn't even get cold at night. The result is your apartment gradually heating over a period of days / weeks and turning into a sauna. It is not pleasant.

By the end of that summer I was dreaming about moving back to north america where air conditioning is much more common in rental units.

What Europe needs is heat pumps and lots of them. More efficient heating, simply run them in reverse during a heat wave for refrigeration.

Most of the Continent is mild enough in winter that an air-loop heat pump will reliably heat throughout the winter, and these aren't more expensive to install than other heating systems, they're less energetically intense to operate, and they provide cooling on demand.

Problem with that is electricity is expensive in Europe. Of course as you know Europe varies a lot between Portugal and Romania. While the first has a balmy 10C in winter daily low, colder areas can easily have -10C, -15C at night. That's the minimum operating range of a heat pump. That's a 30C difference to work through. That's why they have cheap (Russian) gas, it has the biggest energy density (and nuclear). Ground-source heat pumps would work better in continental Europe but they are expensive to install (I have only seen them in new build villas).

Putting the gas into electric generators and using that electricity to heat is more economical than burning it in a furnace for heat, heat pumps are just that much better.

I agree that the national programme must be more detailed than just declaiming "heat pumps!" and calling it even.

I gestured vaguely at the existence of parts of Europe where cheap mini-splits might not be sufficient, let's just agree I'm talking about the places where they will be.

Apologies if my comment made it seem I disagree with you. Air-source heat pumps can definitely be used in many countries here, in fact they are already popular in the UK, and gaining popularity in Spain, due to their efficiency.

I grew in Southern Europe (around 30C every day in summer, more in full sun) when no-one had aircon at home and no-one had aircon in cars.

It's hot, you live with it. I'm sure it's worse on the other side of the Med.

It's one of the reasons the traditional 'siesta' exists and towns and villages are virtually dead until 5pm.

The issue I have with aircon is that it makes people ignore the local climate and, worse, actively fight it, which requires even more aircon.

Staying indoor in 24C air-conditioned spaces conditions the body so badly that even 28C starts to feel bad. I noticed this in my own behaviour and thought of changing it last month. For a change, I decided to drive without air conditioning. It felt bad for a few minutes, then it gets better and when I come back to a cooler place it feels like heaven.

Exposing yourself to the elements is greatly rewarding.

That's actually true. I had a car with A/C in southern europe which I traded in for one that doesn't have one (don't ask how). The first month was brutal but this year it's been already 30C+ and I don't even feel it.

People used to keep all windows open to get the cooling airflow. Now they keep all windows closed with aircon on.

> It's hot, you live with it.

For the average person, yes. But old and vulnerable people do die from it.

30c isn’t a point of reference for hot temperature.

30c in Castilles and Madrid is nothing. Siesta for that it's ridiculous. No one does that. What we do it's to have lunch. Siesta it's for days bordering 40 and up. Also, beware of the stereotypes. You will freeze up in 3/4 of Spain if you dare to get out in shorts and flipflops on Winter as many tourists do.

Yeah it's a temporary effect and once the walls have heated up, it actually makes it worse since it retains the heat at nighttime as well.

You need to drill down to access the constant temperature in the ground, to be able to really counterbalance the differences in the air temperature. Once you've drilled down I guess you can make a passive or minimal energy circulation system that would be much more energy efficient than air conditioning.

It’s called a geothermal heat pump and they’re quite efficient in the places they can work (which is basically anywhere that has enough temperature differential during the year).

I had an issue with this last fall - had my AC go out in the fall when it had been over 80F for the last few months. Outside, it would be 70 during the day and 50 overnight, but there was so much heat in my walls/floors that I literally couldn't keep my apartment below 80. If I opened every window and door, I'd get down to 75 or so, but it would be back to 80 within an hour, even when the temperature outside was significantly cooler.

It's great in the winter though. I haven't had to turn my heat on in years.

Northern Europe complains of the heat in the summer - they have nice radiators for the 7-9 months that need heating, Southern Europe complains of the winter cold because of the lack of insulation and central heating.

That’s so weird to me - why on earth would you skimp ion insulation? The stuff barely costs anything and it helps keep the place cool in the summer as well as warm in the winter

> We rely to much on technology to build these ugly boxes instead of also considering the building shape and position itself.

Just to make a silly pedantic af point, those building structures are also technology

Older European buildings are horrible to heat in winter, they are massive waste of energy.

I'm curious whether the people who designed those old buildings back in the day really thought about cooling or it was just a welcome (as long as heatwaves don't last too long, as mentioned in other comments) side effect of making those buildings with long lasting materials (lots of large bricks and rocks) of those days.

I deployed my own design (not calculated, eyeballed) of a buoyancy based passive cooling at my parents home near Mumbai, India. It did make a measured difference of approximately (temperature meters aren't very accurate) 2 degrees Celsius. I have been reading a lot in my spare time and your blog looks like a nice read.

My point is, is 2 to 3 degrees Celsius enough? From what I read is that I need to really move very large columns of air to make a sizeable impact. TBF my energy bills did come down by ~10%

I’m not that familiar with hot temperatures but intuitively I would think that a difference of 2-3 degrees (Celsius) when temperatures are already high at around 40-45 to be noticeable.

For example if you go from 40°C to 37-38 that’s a quite good improvement if you don’t have to spend energy for this. I don’t know if that also applies to more extreme temperatures like 47°C, I cannot really imagine how that feels like.

At those temperatures heat stroke isn’t far away regardless of humidity. These aren’t temperatures to target 2-3c reductions as a safe goal, either.

Ref: lived in LV,NV for a decade.

From what I understood 2-3°C is not a safe goal but something you can get from the passive cooling solution the initial commenter mentioned. I would guess you can add extra active measures on top?

At some point the thing to do is give people shovels and tell them the roof of their new dwelling has to be at least 2 meters/6 feet below the surface. Or use modern tech.

Got a point there, we as a species lived in 'caves' for a long time, it's only the past 2000 years or so we gave up our nice caves/mud houses. In my region in Europe people still lived in straw mudhuts/semi dug-in houses up until 100 years ago. Somehow that became uncool so we deal with modern people problems.

"uncool" !@!

how does this work where there are heavy rains in that part of the world, each year? desert, sure..

Very good ideas but as far as India goes, adoption might have to consider monsoon, winter-snow in some, which again might require more tweaks based on more tests.

Another aspect is how real-estate and building construction works in India, across rural and urban regions.Some of the regions have strong clouts of companies that control building/development in urban spaces, while supplies and other aspects in rural region.

Can see the realties changing and newer construction projects taking in newer & greener designs, in both urban and rural regions, but its got a long way to go!

How much do these things work when the wet bulb temperature is over 90F?

This would be my concern too. People fail to understand how in heatwaves there ceases to be cold air to move around. Everything heats up. It's brutal.

At that point you need to put your heat exchanger pipes underground, which is more annoying than air-based AC but not insurmountable. The temperature 20 feet underground will be about 50 F year-round. Of course, if a city of millions tried to do this all at once I have no idea how the local ground temperature would react.

> 20 feet underground will be about 50 F year-round

Is that the case in India? I was under the impression that while underground temperature is consistent across seasons, it does vary considerably across climates, with warmer climates generally having higher underground temperatures. For example, while much of the central US has underground temperatures around 50F, southern Florida, California and Arizona have areas with temperatures in the upper-70s[1].

[1] https://www.builditsolar.com/Projects/Cooling/EarthTemperatu...

I can believe the ground temperature is higher nearer to the equator. At the same time, you don't need the ground temperature to be very low, just low enough for the heat exchanger to function. Alternatively, you can dig deeper until you hit a lower temperature.

Thanks for the excellent resource. A big part of this problem is self inflicted.

We used to have thick mud walled houses which stayed cool during scorching heat. People who could afford would go with stone constructions. Things such as sun and wind direction were also considered while constructing the houses. All that knowledge is discarded in favour of high rising concrete jungles.

But all that is replaced with concrete based constructions with almost no insulations. This makes inside even more uncomfortable than outside once the wall have absorbed heat. Commercial construction is even worse with lots of glass.

Also I think this needs to be deployed an large scale. It uses passive radiative cooling http://skycoolsystems.com/

- paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum.

- thermochromic windows

> - paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum.

paint is not free and needs replacement every few years. hardly a solution.

The surface finish of walls may also make a difference. Rough vs smooth and something like that doesn't fade as quick as paint itself.

So you are looking for a free magic solution?

I mean, I like houses made from big stones but it is probably cheaper to paint an existing house, instead of tearing it down and replacing with stonewalls.

Probkem is that it does not scale globally if you can only rely on short term efficacy

No solution is free and needs no replacement.

> - paint that has high emissivity in the IR window and high reflectivity in the rest of the spectrum.

Does such thing exist?

And, doesn't high emissivity in the IR mean high IR absorption as well ?

It's a fairly recent development[0], a few years before that the principle was demonstrated as a special surface coating on smooth surfaces rather than paint. And it's about the IR window[1], which is smaller than the whole IR spectrum. And sunlight delivers most of its energy in visible light and near IR, so there isn't a problem with reflecting the incoming light while radiating away into cold space in the IR window[2].

[0] https://ceramics.org/ceramic-tech-today/materials-innovation... [1] https://en.wikipedia.org/wiki/Infrared_window [2] https://www.researchgate.net/figure/Illustration-showing-des...

There is nothing worse than spending a heatwave in one of those valleys of concrete and glass we call "office towers".

Yeah, and everybody turns AC to maximum, we have record energy consumption for each heatwave, whereas at home I feel more comfortable with just a big fan.

Spanish houses are made of ventilated brick without insulation so they stay really nice even when outside temps are touching 40C. Of course the price to pay is it's 'freezing' between Jan-March.

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