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Saudi Arabia is planning a skyscraper city which is 500 m tall, 200 m wide, and 170 km long. It'll have an all-glass facade. So, a concern is that the glass will reflect the heat until the surroundings become incredibly hotter as a result. Although the mode of the high and low temperatures of the region is 30°C, it is in the top five globally when it came to solar radiation exposure. Will the glass reflecting excessive heat really be an issue? If so, what can be done to mitigate this? Thank you!

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    $\begingroup$ That link makes all the difference... $\endgroup$
    – Solar Mike
    Commented Dec 28, 2022 at 22:24
  • $\begingroup$ It won't matter after the entire thing is buried in sand. That's gong to be one hell of a sand fence. $\endgroup$
    – Phil Sweet
    Commented Jan 29, 2023 at 15:42
  • $\begingroup$ Think about it this way: is glass reflective at all? Yes. That means it reflects light, and concentrated light can make heat. Now, if by heat you specifically mean long thermal IR radiation, that's a different story. $\endgroup$
    – DKNguyen
    Commented Mar 1, 2023 at 17:45

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Yes it is an issue.

Happened in London and damaged cars. Lots of reports about it and some include what they did.

Edit: here is a link to one of the reports from the time and it mentions the solution: enter link description here

Thanks to Google - amazing what you can find 😀

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  • $\begingroup$ What can be done to mitigate this? $\endgroup$ Commented Dec 28, 2022 at 13:20
  • $\begingroup$ Resd the reports - as I mentioned some include what they did. $\endgroup$
    – Solar Mike
    Commented Dec 28, 2022 at 13:21
  • $\begingroup$ I'm just a layman $\endgroup$ Commented Dec 28, 2022 at 13:22
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    $\begingroup$ @PeerKristijan Google does not discriminate. $\endgroup$
    – Solar Mike
    Commented Dec 28, 2022 at 13:25
  • $\begingroup$ I tried it to no avail. $\endgroup$ Commented Dec 28, 2022 at 13:27
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As the answer by Solar Mike states, yes, it has happened before. One way to mitigate the problem is to install a brise soleil (a sun breaker) on the building. It reduces heat gain and reflection from the windows by deflecting sunlight. In many ways it's a variation on a veranda.

An alternative would be to put retractable shading on the glass walls.

If the architects or owner of the building don't want to "spoil the artistic design" of the building by having a brise soleil, anti or low reflective glass could be used.

Another option would be to angle the external glass walls of the building so they reflected sunlight upwards, above horizontal, and not downwards, below horizontal.

Incorporating some form of shading for the proposed "ultra long residential glass house" would be prudent.

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  • $\begingroup$ "Another option would be to angle the external glass walls of the building so they reflected sunlight upwards, above horizontal, and not downwards, below horizontal." Nope, you can blind pilots and anyone else within about a 100 mile radius doing that. You have to angle the glass downwards several degrees. This happened in Knoxville with the world's fair Sunsphere building. They had to re-glass the top half. And even then, you can sit on cliff-tops 80 miles away and be blinded if a panel hits you just right. $\endgroup$
    – Phil Sweet
    Commented Jan 30, 2023 at 20:57
  • $\begingroup$ Low-reflective glass means more energy absorbed by the building. That's not what you want in 30 degree heat with bright sun. $\endgroup$
    – david
    Commented Mar 3, 2023 at 2:30
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The building in London that other's have mentioned is a bit different from the Saudi Arabian plan.

In the London building, the glass face was concave, so it would focus the sunlight onto a small area, resulting in very high temperatures. There is a similar building in Sydney, Australia.

However, in the Saudi case, the building is intended to have flat sides so the solar concentration should not occur.

Nonetheless, this would still double the level of solar radiation in the areas that will have the reflection from the building sides, plus direct sunlight. So the mitigation methods mentioned would still be useful.

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It would be an issue if "The Line" wouldn't be build in an area that is largely uninhabited, infertile desert. Yes, the desert sand on the southern side will get a bit more sunlight from the reflection. If there was anything there that mattered, roads, parks, parking space, buildings, farmland, vegetation, etc., that could be a problem. But it's really just desert sand that gets a bit hotter than it already gets.

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