If We Utilized More Smart Windows, We Might Not Need Air Conditioners Anymore 

If We Utilized More Smart Windows, We Might Not Need Air Conditioners Anymore 

The unending cycle is, for now, the weather and climate get hotter, we need air conditioners to cool down, but the emissions from ACs will make the warming worse. Well, we can start reducing the need and use of these room coolers through utilizing smart windows.  

Smart windows can control the amount of heat that comes to and goes off a building, reducing the need for ACs and thus making buildings more energy efficient. 

Around 75% of buildings in the EU alone are not efficient in energy, and countries all over the world are trying to change that. It’s only recently that we design better windows that uses modern technology to reduce air conditioners. 

Ioannis Papakonstantinou, a professor of nanoengineering at University College London, has done a research project called Intelglazing. It uses new ideas in nanotechnology and photonics (the physics of light) to create nanometre-thin window coatings that better insulate buildings. 

To tell the truth, this isn’t something completely novel because there were trials before. However, all those efforts weren’t fruitful—they either blocked out too little sunlight or were too costly to make. 

“If you start blending these (window) coatings with nanotechnology, then you can push the performance boundaries to much higher levels,” said Papakonstantinou. 

Intelglazing glass 

This technology has two parts. The first is a microscopically thin layer of nanostructured glass with a shape like tiny hair combs, measuring less than a micrometer in height. These “nanocomb” structures overlap with each other and scatter sunlight, reducing the glare that enters through the window. 

Secondly, the researchers have experimented with a material called vanadium oxide, which can attach to the nanocombs. It can change its color depending on the temperature. For example, on hot days, the material changes its structure—darkening and deflecting most of the warming. On cold days, it’ll lighten and let most of sunlight in. 

Manufacturers can plaster on this layer directly on top of new windows, but it’s DIY friendly too because we can apply it to old windows as an adhesive layer of polymer film. According to Papakonstantinou, manufacturers can customize windows or films with these layers to switch on at a different temperature point. 

Papakonstantinou said, “You can change the chemical composition of vanadium dioxide in a way that it can switch at a higher or lower temperature, so you have some quite good control.” 

What he means is that manufacturers from southern Spain could block out sunlight at a lower temperature to prevent buildings warming up during the day. On the other hand, people who live in northern Sweden will want to get as much warmth from the sun as possible, so their windows could only start blocking out sunlight at a higher temperature. 

water droplet on a hydrophobic surface. photo by Eskozxz Wikimedia Commons

Self-cleaning windows 

Once we’ve utilized Intelglazing technology, we’ll get the benefit of self-cleaning windows. This happens through the material’s hydrophobic feature, so rain will quickly run off the glass and pick up any dirt along the way. Adding this technology to windows and glass in skyscrapers would be greatly advantageous. 

Through the lack of need of extra energy to activate vanadium oxide, this project aims to reduce people’s energy use by 25% by blocking or allowing sunlight when needed, and be more than 50% more efficient than existing window technology.  

Papakonstantinou said that window retrofitting technology has changed drastically since the project started in 2016. He added that when he discussed the project in the mid-2010s, nanotechnology in windows was unheard of. Now it’s started to be a much-discussed topic. 

Professor Per Heiselberg of Aalborg University in Denmark said that discussions on retrofitting buildings have been around for decades. It’s only recently that the environmental element has become a priority. 

Heiselberg said, “It has been the topic for 40 years, but of course the argumentation has changed. Now the focus is to reduce your carbon emissions and avoid greenhouse gases.” To give you some context, before, people were saving energy because they didn’t want to be dependent on countries in the Middle East, which had an oligopoly on oil supply. 

Ventilating buildings 

The smart window technology will provide ventilation for older, retrofitted buildings, where installing modern ventilation systems like ACs is difficult or expensive.   

Heiselberg said, “(A window is usually the) weak part of the envelope because it’s typically leaky and not so well insulated. On the other hand, it’s also where we get some heat from the sun into our buildings.” 

Using these smart windows could provide better shade from the sun and bring fresh air into a building, which is useful for retrofitted buildings. Modern windows we have right now are more airtight, causing moisture and emissions to build up in the building. That’ll end up requiring another costly installation to ventilate the building. 

“It can be difficult—especially in old buildings—to find space for pipes and ventilation systems to supply fresh air to the spaces—and all spaces usually have access to the outside through a window. 

Ventilation grid in Old Supreme Court Building in Singapore. Photo by Jacklee Wikimedia Commons

“It would be more cost effective if, instead of installing both a new window and a ventilation system, we use the window for supply of fresh air, and then we use the chimneys or the stacks you have in old buildings for the exhaust of the air,” said Heiselberg. 

This smart window is based on a previous research project in the EU called CLIMAWIN. There’s a small gap of around 5mm in their triple-glazed window frame at the bottom level on the outside.  

What’s the gap for? It allows air to pass in between the window’s glazing layers and be warmed by sunlight. Then, it enters the room through a small valve at the top of the window facing inside the building. 

Result of this project is a preheated draft of fresh air through the window that can leave the building through another ventilation exhaust. 


Currently, the team tries to experiment with different materials that can store unused heat in the windows during the day and then release it at night. Heiselberg said, “During a time where we have sunshine, we can collect and store it,” he said. “And then we also have the possibility to preheat air in periods where the sun is not shining.” 

We can shade this material from the sun when it’s really hot. So instead of storing latent heat, it cools the air passing through it. Researchers are developing another idea, which is fitting the windows with sensors to know the optimal time to store and release heat. They’re also planning to add mini fans to control the direction of the airflow. 

Heiselberg concluded, “Renovation of buildings is carried out all the time because components have a certain lifetime and need to be replaced. It’s important that when we do this, that we do it in the most energy efficient way so we don’t replace an old window with a poorly performing new window.” 




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