Empa scientists have developed a model that predicts how well a garment will keep one warm. This eliminates the need for test runs and reduces the development period of a garment by up to 90 per cent. The thermal comfort is not primarily determined by its fabric. The crucial factor is the air gap between the body and the outermost layer of clothing.

In winter, it can look sunny and warm. But as soon as one is exposed to the wind, one may start freezing. The thermal comfort of a clothing is not determined by its fabric. “Much more important are the air layers between the body and the fabric,” explains Empa researcher Agnes Psikuta. “Air gaps are responsible for more than 70 per cent of a garment’s thermal properties.” This is because air is an excellent insulator. Thus, clothing insulates particularly well when there is a lot of air between the body and the outermost layer of clothing. If this air escapes, the insulation suffers and one begins to freeze.

To date, most scientific models for predicting heat loss have been based mainly on the properties of fabric that have been used to manufacture a piece of garment. Fabrics, however, fall very differently when a body moves. This also changes the insulating air layers; but only a permanent layer can insulate well.

Researchers have, therefore, looked for solutions to calculate the change in air gap thickness during movement. “We used computer programmes developed for the fashion industry as a basis. These programmes simulate the situation on a catwalk. Designers can create a virtual model of a garment and see how their newly designed clothes look on a person in motion.” It turned out that these computer programmes can accurately predict how clothes will drape on the body.

The software developed by Agnes Psikuta and her team combines different mathematical models that interact with each other. In addition to air layers, the programme predicts the thermal comfort of the wearer as well as the influence of sweating or body movements on the garment. Finally, a cutting pattern is transformed into a virtual piece of clothing.

The programme can also help to develop an optimal outfit for running in autumn. “Even before the fabrics or the aestetic design have been determined, our software calculates the necessary clothing should fit,” explains Psikuta. And all this not only for standard sizes. “Our programme can shape the avatars according to different body types and sizes. If, for example, something is to be developed for particularly muscular, curvy or slender people, we can adapt the programme accordingly.”

The programme helps to replace countless prototypes for the development of new clothing and functional gear. As this also eliminates the need for time-consuming test runs, the development period is reduced by up to 90 per cent. “How much time we can actually save depends greatly on the product in question and its complexity,” says Psikuta. “For instance, protective clothing for firefighters – ultimately a health- and life-saving piece of equipment – has a very complex structure, while a sports T-shirt, on the other hand, is quite a bit easier.”

Empa is working with industrial partners to bring the research into practice. “They come up with new ideas, and we support them with our technology and help them to develop their apparel in the shortest possible time,” says Psikuta.