Windows provide natural light and a view of the outdoors, giving buildings a sliver of nature.

When it comes to temperature regulation, however, windows are also the weakest link in a building’s walls. Windows let out heat in the winter and trap unwanted heat in the summer. As a result, air conditioning and heating systems run much more.

Adapting Windows

A team of researchers from Southeast University and Concordia University recently reviewed a passive solution to this issue called “thermochromic smart windows.”

In a recent study, researchers closely analyzed thermochromic smart windows, which use special materials that naturally change how they handle light based on the temperature. All of this is done on its own without external power, sensors, or tricky control systems to work.

When it gets cold outside, the glass stays mostly transparent. This lets daylight and solar heat into the building to warm it up. Then, when it gets hot, the glass reduces the amount of solar heat coming through, especially near-infrared light.

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Great for Hot Climates

Representational image of lobby windows; Photo: baona jnr/Shutterstock

The researchers, Weiqiang Ma, Sai Liu, Junqi Wang, Fariborz Haghighat, and Shi-Jie Cao, reviewed several materials that make this possible. The list includes vanadium dioxide, halide perovskites, hydrogels, liquid crystals, and ionic liquids. These materials are great at blocking heat and adjusting to different temperatures.

There were some challenges that the researchers had to overcome, including the materials getting hazy, changing colors strangely, and getting damaged by moisture. They also suffer from general wear and tear over time. As the authors stated, “the key challenge is no longer only finding better materials, but translating material-level performance into reliable building-scale applications.”

Moving forward, the industry must balance factors like transparency, response speed, and long-term durability. Additionally, the windows have to look good.

According to the researchers, the windows are incredibly useful in hot regions where cooling is the main concern. In cold climates, however, if the glass switches at the wrong time, it might actually block the helpful winter sun.