I've seen some new projects in Bogotá and Mexico City that use glass that changes based on sunlight. I'd like to know if they actually work or if it's just hype, and how much more expensive a facade like that is compared to regular glass.
Smart glass (electrochromic or thermochromic) does work, but it's not magic either. The real ones adjust their opacity based on light or temperature, so in theory they let less heat through when you need to avoid it most. The thing is, the actual difference in energy consumption depends a lot on the climate, the building's orientation, and whether the system is properly calibrated. In places like Mexico City or Bogotá with variable climates, they do help, but people sometimes exaggerate the impact.
What is true is that they cost quite a bit more. Smart glass can run you double, sometimes triple the price of regular glass, depending on the technology. If you add the cost of installing the control and maintenance systems, a complete façade ends up being significantly more expensive. On top of that, a lot of projects still use these windows more for marketing than for any real efficiency calculation, so there's definitely some hype involved.
That said, if the project is done right and the glass is properly oriented and configured, it does pay back part of the extra investment through lower air conditioning bills over the long term. But don't expect it to be the definitive solution to climate change or anything like that; it's just one tool among several.
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