In winter, houses do a very simple and very expensive thing: they let heat escape just as energy is needed outside to put it back inside. In Europe, space heating and hot water absorb approximately 77.6% of domestic energy consumption, a share that the European Commission often rounds up to the almost 80% that weighs on the bills of millions of families. On a global scale, then, the heat in buildings continues to rely largely on fossils: according to international data, in 2020 62% of heating in buildings came from these sources. Within this scenario, a group of engineers and researchers from the University of Massachusetts Amherst tried to shift the problem from the walls side, treating external walls as active surfaces capable of capturing solar heat.
Treat the external walls as if they had to dress themselves in winter
The image chosen by the researchers works because it comes from a daily gesture. When a person is cold, he adds a layer. This is where this sort of “sweater” for houses was born: a removable system to be applied to the facades, organized into panels that can be fixed to the external walls. The heart of the project is a photothermal fabric treated with a special dye based on PEDOT-Cl, a conductive polymer already known in advanced materials research. The idea aims to transform the external walls into passive heat collectors, without invasive interventions on the entire building. The researchers also insist on another point, less technical and very concrete: these panels can be printed and designed in such a way as to better fit into the aesthetics of the urban context, because such a technology, to truly circulate, must also be able to fit well on houses.
The material used is thin and light, closer to an umbrella canvas than a traditional building panel. Precisely here lies one of the most interesting aspects: photothermal dyeing can be applied on different textile supports, therefore also on economical bases. When the sun hits the surface, that coating absorbs the radiation and quickly converts it into heat, with behavior comparable to that of a dark metal surface exposed to light. That heat then passes inside and helps warm the air in the building. It’s a very direct logic, almost brutal in its simplicity: instead of just asking the system to do the heavy lifting, we try to get the shell of the house itself to collaborate.
The results released so far remain very promising. According to simulations and initial tests reported by the team, this textile skin could reduce heating energy costs by about 15% in a residential home located in a cold climate such as Massachusetts. In large residential buildings, up to a 16-storey building, the estimated cut reaches 23%. Another immediately striking fact also appears in the same promotional material: the average effect can lead to an increase in internal temperature of approximately 4.8 °C over the course of the day. To make the comparison even clearer, the researchers observe that a traditional renovation done very well, in certain cases, can result in energy savings of around 2%.
Here it is best to keep your feet firmly planted on the ground. The project has demonstrated the concept in the laboratory and in simulations, while the transition to full-scale field tests remains to be completed. The research group itself says it: more data and full-scale prototypes are needed to understand how this solution behaves outside the rendering images and inside the daily life of buildings, where exposure, rain, wear, assembly, maintenance and real performance season after season count. The point, however, remains strong: lightening the dependence on fossil fuels and reducing the weight of heating with a light, removable and potentially accessible layer would change a lot, especially in existing buildings where major works cost too much or arrive late.
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