![]() Materials composed of recycled polyester fibers had the lowest effusivity and would therefore feel the warmest next to your skin on a hot day. But in our upcoming paper to be published, we found the exact opposite. If you are a connoisseur of sports apparel, you probably expected that a shirt made of 100% recycled polyester fiber-based materials would have performed the best, and cotton ones the worst. The back side of a jersey knit has stitches assembled horizontally and is usually on the inside of a T-shirt. The face side has vertical rows of knit stitches and is the outside of a T-shirt. Jersey knits have distinct face and back side aesthetics. The face (left) and back (right) sides of a jersey knit material have different effusivity properties. To keep the competition fair, we made sure all of the fabrics were made the same way – with a common jersey knit construction. To get to the bottom of this question, our research team collected effusivity data from seven sport T-shirt materials made of polyester, recycled polyester, rayon, wool, nylon, cotton and spandex fibers. So, what T-shirt material provides athletes the best cool touch feel? My colleagues and I wanted to identify materials that have high effusivity values so that the next time you are getting ready for a pick-up game of basketball in the grueling heat, you could choose a T-shirt that will give you a cool feeling next to your skin. This same principle can apply to athletic T-shirts. On the other hand, if you got out of bed and put on some woolly slippers - your bare feet and slippers have effusivity values that are closer together, therefore your toes will feel super cozy. ![]() This happens because the wood has a higher effusivity value, so it feels much colder. On a winter morning, differences in thermal effusivity are what make stepping onto a cold hardwood floor with your bare feet so much less comfortable compared to when you’re wearing wool slippers. Even when a piece of natural rubber and silver are the same room temperature, the silver will still feel colder because it has a higher effusivity value. For example, air has an effusivity value of 6, natural rubber is 518, human skin is 1360 and silver is 23688. The lower that value, the warmer a material will feel. And we are less likely to have air-conditioning.The higher the thermal effusivity value a material has, the cooler it will feel to the touch. ![]() Buildings in the UK are also designed to keep heat in, compared to hotter countries. They said: “This is made worse given that we are experiencing more 'tropical nights' - nights where the temperature doesn't go below 20C, meaning we get no respite from the heat and time for our body to recover. If humidity is high, it is harder for the human body to keep cool as your sweat doesn't evaporate as quickly.”Īnd if you are struggling to sleep at night at the moment, the spokesperson had an explanation for that too. So why is it that we feel like we’re actually going to melt when there’s a hot day over here? Well, the Met Office has got an explanation as to why UK heatwaves feel so much hotter than they do overseas.ĭuring last year’s UK heatwave, a spokesperson from the Met Office told MyLondon: “The level of humidity can be higher in the UK than in continental Europe. When you’re sitting next to a pool with a cold drink in your hand on an overseas holiday, it’s not likely you will be complaining that it’s too hot, right? However, when temperatures reach the same levels in the UK, the heat often feels unbearable, doesn’t it? ![]()
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