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My world has a city of glass found along the outskirts of a desert. I decided on this because sand can become glass and so it was a huge resource that could be used for building. However, the concern has come up that it would bake the citizens alive. Originally, the glass was textured and thick enough to look black, and this is what caused concern.

Is there any way I can have a city of glass in the desert without cooking its denizens?

My first thought is Obsidian. There are problems with this; it's a volcanic glass, and you're in a desert, but conceptually, the idea is reasonably sound.

I'm going to assume for the purposes of my answer that by 'desert', you mean a hot, dry sandy desert like the Sahara or Gobi, not the strict definition of a place with no rainfall that could also include Antarctica. I'm inferring from your question you're only looking at places with lots of sand and hot days.

In many countries, we use double glazing as an insulative material. There are even now triple glazing products, which effectively put 2 air pockets, or vacuums, between you and the elements. It's suprisingly effective, although obviously not as effective as walls with thick insulation bats. That said, if your inhabitants can shape a heavily tinted glass like obsidian or even manufacture it from the sand around them, then they can build homes with shelter from the sun via double or triple glazing using glass like obsidian which is (more or less) opaque.

Glass houses in the desert are a bad idea because of the greenhouse effect - the sunlight getting in gets trapped and heats up the internal areas of the glass house even further. Great if you're growing tropical plants in Scotland, terrible as a desert housing solution. What obsidian would offer is the ability to block the sun from getting in in the first place. You get shade which in the desert is important. What you don't get is a shelter medium that can breathe, and release the trapped heat. Glass can act as a thermal mass though, which could actually work in your favour on this point.

Deserts are known for being hot through the day, but they're also very cold at night. Why? because they have no water around them, meaning a very low thermal mass. Your obsidian would spend the day baking in the sun, retaining heat. because you've double glazed, you won't feel that heat until early evening, but through the night it starts to release it, meaning that it actually serve to keep you warm through the night, when the desert is bitterly cold.

So, if you do it right, all you've really got to do is introduce impurities into your glass that turn it black or some other colour, then build your homes with air gaps between panels, and you have a good chance of building homes that can regulate temperature reasonably well. You're still going to be hot during the day, cold at night, but not as much as you'd otherwise be.

Problems

Reflection: Just as swimming will burn you faster than sunbathing (light reflecting off the water), light reflecting off the glass simply means that much more light to burn you.

• Solution: buff the glass to reduce reflection.

Refraction: There could easily be spots in the city, despite all efforts, that act as magnifying glasses (ants... magnifying glass... mine was a sordid childhood). Corners are your biggest problem, but any angle can create magnifying refraction. It doesn't actually need a curve (curves create precision for, e.g., distortionless vision, but any type of "bulge" will cause magnifying refraction).

• Solution: cut insets that break or redirect (like a prism) the "flow" of light through the glass.




• Solution: Color the glass to increase its opacity.

Benefits

Visibility: You can see your enemy coming! You can see where they are outside the wall! They can also see you taking a shower... so it might not be that much of a benefit.

• If this is desirable, then the previous solutions must be used carefully or the visibility is lost.

What is it about a glass city that intrigues you? The fact that it's glass? The transparency? The shiny reflection as the sun rises?

This is a very important question, because it will dictate how you solve your problem. BUT! There's one solution that might give you everything you want.

Thin silvering

Silvering glass is what makes mirrors. Thin silvering (silvering you can see through) is that makes one-way mirrors. So, anywhere in the city that wants privacy, you apply thin silvering inside that place or room. Thus, people can't see in, but they can see out. Light can't burn through into the room — but it would cause a horrible headache for anyone approaching from the wrong angle.

And if you really want to take advantage of that, use prisms as building roofs such that the light of the morning is redirected and cast behind the city, and vice-versa for the evening. Thus, between the prisms and the silvering, there isn't an approach to the city that isn't blinding.

Please note that I've made a few assumptions as to why you asked your question. If my assumptions are wrong, let me know and I'll adjust my answer.

Oh... and your buildings are going to want a LOT of ventilation. Preferably from holes dug deep in the sand. Really deep. But that's just an issue of construction.

You Need a Windcatcher House

Sheets of glass for the most part is not a great building material. Glass in the form of bricks can be structural, which will allow you to build up. You could build a glass house and yes, it would get hot in the desert. But proper desert homes don't get hot. Instead of building a house with four walls and a pitched roof, you just need to incorporate a few features to make your desert home comfortable.

You Need a Windcatcher

A windcatcher, also known as a malqaf, is a tower higher than the rest of the structure which has a shaft that leads from the tower to the living facility. The open face faces the prevailing wind, which catches it and pulls it down the tower, which cools your glass structure. The windcatcher does not necessarily cool the air itself, but rather relies on the rate of airflow to provide a cooling effect. They have been used in desert climates for thousands of years.

How about Making Ice?

You might find that this structure cools your home, but you want an extra blast of cooling for water storage, food storage or making ice, using only the wind. What you need to do is add another tower which faces the opposite direction of the prevailing wind. With this tower, the wind is drawn upward using the Coandă effect.

It's more effective with a basement and if your settlement is feeling industrious, an underground water channel with holes spaced along the length of the channel to the basement of each home. The ancient Persians called this channel a qanat.

• https://en.wikipedia.org/wiki/Coand%C4%83_effect


• https://en.wikipedia.org/wiki/Windcatcher


• https://en.wikipedia.org/wiki/Yakhch%C4%81l


• https://en.wikipedia.org/wiki/Qanat

This combination of design elements woll keep your desert homes much more manageable and energy efficient because you're not spending resources on active cooling. It's passive and it works.

Good luck staying warm.

Look at how termites in Africa build their colonies. To prevent from being cooked inside their homes, they build tall chimney like structures. The sun heats the chimneys, causing air circulation throughout the colony.

If your cities utilize a similar design, the city could remain fairly comfortable at the base levels. You use these convection currents throughout your city for other functions as it suits you.

https://www.sciencemag.org/news/2015/08/how-termite-mounds-breathe
here is a little article that may help.