# Do "heat generating" clothes really work? **URL:** \ **Category:** Factual Questions\ **Created:** [January 30, 2011, 9:55pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558 "2011-01-30T21:55:31Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![xoferew](https://avatars.discourse-cdn.com/v4/letter/x/e9a140/32.png) [@xoferew](https://boards.straightdope.com/u/xoferew)\ **Post date:** [January 30, 2011, 9:55pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/1 "2011-01-30T21:55:31Z")
I bought tights, shirts, scarves, and hats from Uniqlo this year for myself and as Christmas presents. I can’t tell how well they work and how much is a placebo effect of thinking they work. They supposedly use the moisture from your body to generate heat. I’m thinking they are on par with silk winter underwear: very thin, and quite warm considering the thinness. Plus they don’t look like underwear. I like being able to layer a regular shirt over a thin “heat-generating” turtleneck and avoiding the bulk of sweaters. But this could just be “keeping heat in” not “generating heat.” Even if it technically works it could be just an unnoticeably tiny effect. There was one time I think I really felt the effect, when I went to sleep with the tights on under a thick comforter, and maybe because I started sweating, they heated up enough that I woke up and yanked them off. But again, maybe it would have been equally hot with regular tights. And heat-generating clothes that cook you when you sweat profusely are not ideal. Here is their scientific explanation: [http://www.uniqlo.com/ht\_w/us/](http://www.uniqlo.com/ht_w/us/) Does it sound plausible? ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [January 30, 2011, 10:03pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/2 "2011-01-30T22:03:06Z")
It doesn’t actually explain how it works and those thermograms look almost identical. ---
**Author:** ![xoferew](https://avatars.discourse-cdn.com/v4/letter/x/e9a140/32.png) [@xoferew](https://boards.straightdope.com/u/xoferew)\ **Post date:** [January 30, 2011, 10:07pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/3 "2011-01-30T22:07:55Z")
> [@runner pat](#): > > It doesn’t actually explain how it works and those thermograms look almost identical. Maybe I could do an experiment. Wear the heat-generating tights on one leg and regular tights on the other and jog on a treadmill to work up a sweat, and see if I detect any difference. I guess I could tie the extra legs around my waist. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 30, 2011, 10:12pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/4 "2011-01-30T22:12:03Z")
They clearly can’t generate heat, since they don’t have an energy input (unless something in the cloth is reacting chemically with sweat, in which case they’d wear out very quickly). And sweating will cause cooling, not heating (that’s why we sweat in the first place). ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [January 30, 2011, 10:15pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/5 "2011-01-30T22:15:29Z")
nm, **Chronos** beat me to it. ---
**Author:** ![j666](https://avatars.discourse-cdn.com/v4/letter/j/9de0a6/32.png) [@j666](https://boards.straightdope.com/u/j666)\ **Post date:** [January 30, 2011, 10:28pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/6 "2011-01-30T22:28:59Z")
> [@xoferew](#): > > Here is their scientific explanation: [Women's, Men's and Kids' Clothing & Accessories | UNIQLO US](http://www.uniqlo.com/ht_w/us/) Does it sound plausible? As mentioned above, that is not a scientific explanation. “When HEATTECH absorbs body moisture, tiny droplets generate heat”. What? Droplets of the fiber? If the material does trap still air, it will insulate (Heat Retention section). Wool, a protein fiber, does generate heat when wet; something like the water allows the helices to go to a new lower energy configuration, releasing energy in the process. I don’t remember exactly, but some one will probably come along to correct me and give you the full details soon enough. However, the items seem reasonably prices, if they are fairly durable. I’m very interested in the socks. The biggest mystery is that only the men’s material absorbs water and only the women’s is soft. No, the biggest mystery is that a heat-generating clothing has a spring/summer line. ---
**Author:** ![j666](https://avatars.discourse-cdn.com/v4/letter/j/9de0a6/32.png) [@j666](https://boards.straightdope.com/u/j666)\ **Post date:** [January 30, 2011, 10:53pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/7 "2011-01-30T22:53:07Z")
okay, according this site, wool and water can generate heat, but it is the water, not the wool. > **[How does wool keep you warm even when it's wet?](https://www.mapquest.com/travel/outdoor-activities/hiking/wool-when-wet.htm)** > > Sheep wear the stuff all the time, and they seem to keep pretty cozy and dry. What is it about wool that keeps you dry in the rain, cool in the heat and warm in the cold? “The hydrogen bond of water, H2O, is actually broken, creating a chemical reaction with the wool fiber molecules to generate heat when it has taken on a lot of moisture.” This article from **1960** concludes the bacteria in the wool produce the heat (I think, I just scanned it) > **[jbacter00477-0019.pdf](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC278981/pdf/jbacter00477-0019.pdf)** ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [January 31, 2011, 2:56am UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/8 "2011-01-31T02:56:21Z")
Heattech really does work. Anecdote time, I was in Hokkaido and freezing my tropical monkey butt off, when my newlywed wife and I came across a Uniqlo. We actually just wanted new long sleeved tshirts, not having packed enough, and these were pretty cheap and reasonably fashionable. Hooooboy. We went back for more. And more. And bought some home for our parents to bring on their winter trips (they loved them too). I don’t know if they generate heat, or trap heat (they’re actually surprisingly cool at “normal” temperatures), but they work, and are cheaaap. ---
**Author:** ![Pyper](https://avatars.discourse-cdn.com/v4/letter/p/5f9b8f/32.png) [@Pyper](https://boards.straightdope.com/u/Pyper)\ **Post date:** [January 31, 2011, 3:46am UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/9 "2011-01-31T03:46:33Z")
I have two shirts and a scarf from Uniqlo. As far as I can tell, there is absolutely no difference between these items and regular clothing, heat-wise. However, the anti-odor claims do seem to be true (no stink after sweating) and they are great shirts- soft, stretchy, and fit well. ---
**Author:** ![j666](https://avatars.discourse-cdn.com/v4/letter/j/9de0a6/32.png) [@j666](https://boards.straightdope.com/u/j666)\ **Post date:** [February 1, 2011, 2:00am UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/10 "2011-02-01T02:00:28Z")
I think anecdotal reports should include the gender of the person, as the material used for men’s and women’s clothes may differ. ---
**Author:** ![Chessic\_Sense](https://avatars.discourse-cdn.com/v4/letter/c/7c8e57/32.png) [@Chessic\_Sense](https://boards.straightdope.com/u/Chessic_Sense)\ **Post date:** [February 1, 2011, 3:16am UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/11 "2011-02-01T03:16:32Z")
> [@Chronos](#): > > They clearly can’t generate heat, since they don’t have an energy input (unless something in the cloth is reacting chemically with sweat, in which case they’d wear out very quickly). And sweating will cause cooling, not heating (that’s why we sweat in the first place). Sweating will only cool you if the water evaporates. If you wear some fabric that absorbs the sweat instead of letting the air carry it away, then the fabric will retain your body’s heat. That’s pretty close to “generating heat”. ---
**Author:** ![spenczar](https://avatars.discourse-cdn.com/v4/letter/s/858c86/32.png) [@spenczar](https://boards.straightdope.com/u/spenczar)\ **Post date:** [February 1, 2011, 3:22am UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/12 "2011-02-01T03:22:50Z")
> [@Chessic\_Sense](#): > > Sweating will only cool you if the water evaporates. If you wear some fabric that absorbs the sweat instead of letting the air carry it away, then the fabric will retain your body’s heat. That’s pretty close to “generating heat”. I can’t think of any way - at all - that the process you describe could be construed as a mechanism of heat generation. ---
**Author:** ![Nunzio\_Tavulari](https://avatars.discourse-cdn.com/v4/letter/n/b9bd4f/32.png) [@Nunzio\_Tavulari](https://boards.straightdope.com/u/Nunzio_Tavulari)\ **Post date:** [February 1, 2011, 4:08am UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/13 "2011-02-01T04:08:17Z")
> [@runner pat](#): > > It doesn’t actually explain how it works and those thermograms look almost identical. Maybe I’m mistaken, but it appears to me that the Heatech thermogram is of the front of the body while the 100% cotton is of the rear. So they wouldn’t be valuable even if they were markedly different. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 1, 2011, 7:03pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/14 "2011-02-01T19:03:58Z")
Of course, it is possible that the material is just better at retaining heat, and possibly retains heat well even when wet (this is one of the major virtues of wool). But I’d trust the company a lot more if they just came out and said that, rather than making incorrect claims which betray either ignorance or dishonesty (neither of which is something I look for in companies I buy from). ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [February 1, 2011, 8:26pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/15 "2011-02-01T20:26:23Z")
> [@Nunzio\_Tavulari](#): > > Maybe I’m mistaken, but it appears to me that the Heatech thermogram is of the front of the body while the 100% cotton is of the rear. So they wouldn’t be valuable even if they were markedly different. Umm, am I missing something or doesn’t a thermal image of a body just show you the amount of heat it is _losing_? As in those thermal images of houses showing how the badly insulated ones are leaking heat through the roof? Show me a thermograph image where the clothing appears dark blue and I’ll believe it’s keeping the wearer warmer. (Or the wearer has died.) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [February 1, 2011, 8:56pm UTC](https://boards.straightdope.com/t/do-heat-generating-clothes-really-work/569558/16 "2011-02-01T20:56:54Z")
This is true. Some folks had a thermal camera set up in the atrium a few weeks past, and my down jacket made a pretty good cloak of invisibility.