T-Shirt keeps you warmer in water?

Our 3 yr. old grandson is visiting…we have the required “kiddie-pool” in the
backyard. Anyway, it was cloudy yesterday while the grandson was
swimming, there was a rather stout breeze blowing and I could tell that
he was getting a bit cold, even though he insisted he was NOT cold. My hubby
said to put a T-shirt on him, that he wouldn’t be as cold that way. I’m wondering
about this…the T-shirt got wet too, after all.

Thanks much!

dfq

A cotton T-shirt might help marginally in the conditions you describe. It might absorb water and trap water close to your grandson’s skin. The heat from his body will warm the water in the T-shirt, producing a “warm” (relatively speaking) layer that insulates him a bit from the somewhat colder water in the pool. The shirt will also reduce the amount of evaporation from his bare skin, which will also keep him a bit warmer.

On the whole, though, a cotton T-shirt is not by any means the way to keep someone warm in water! :smack:

As I noted, cotton absorbs water, which is 25 times as good a conductor of heat as air. If you are mostly submerged in the water, the T-shirt has no insulating properties, it just keeps a relatively still boundary of water next to your skin. That water warms up from your body and keeps you warm. If you’re at all exposed to the air, evaporation begins to cool down the water in the T-shirt. You’re now wearing something akin to a shirt full of ice! Even on a still day, a wet T-shirt will reduce your skin temperature quickly. In a wind, it will freeze you. :eek:

I am deadly serious. Many cases of hypothermia/freezing to death come from relatively warm but wet conditions (a summer thunderstorm while hiking at high elevations) combined with wet cotton clothing that literally sucks the warmth out of the person. I’ve seen this happen. People come into the first aid station at a ski resort in close to severe hypothermia after spending a snowy day in cotton clothing. Just taking off the clothing helps them recover. The treatment is usually to have them strip naked under a wool blanket, and then apply hot water bottles into the armpits and on the abdomen.

I also remember a diving student who emerged in crisis complaining of extreme cold. We were diving in Monterey, which can be quite cold. The normal protection is a 7mm all-over wet suit, made of neoprene (closed-cell foam rubber). While this type of suit allows water next to the skin (“wet suit”), it traps the water and allows your body to warm it and at the same time insulates this warm water layer from the cold water outside.

Alas, this student had been over-worried by descriptions of the cold, so she decided to take action by putting on a cotton sweatshirt underneath her wetsuit :eek: This of course destroyed the whole purpose of the wetsuit; the sweatshirt soaked up cold water and then started transferring her body heat away from her skin.

Thus the backpackers/athlete’s saying, “Cotton kills.” Don’t wear cotton for any situation in which you want to maintain body temperature. That especially goes for winter sports. Instead, wear non-absorbent materials like polypropylene/Coolmax and so forth; these materials do not hold water at all, and are mostly woven in a way that removes sweat from your skin. The result is dry, insulated skin. In really cold conditions, lay a “fleece” layer over the non-absorbent layer. Polarfleece and the like are an “artificial wool” that traps air,keeping it still and making it an effective insulator. The insulating effect works even if the material is wet, although a sopping wet fleece garment will take some extra heat away from you.

Have a third layer available for windy conditions, since fleece is not wind-resistant. But, in most wind and cold air, a windproof layer will insulate about as well as a non-windproof “insulating” layer. Still air close to the skin is the best insulator.

Your husband would be much better to leave your grandkid without the T-shirt and put up some sort of barrier against the wind.

633squadron–
Thanks for the information. Even though I didn’t realize that so much could
be involved in the “T-shirt question”, common sense told me that sitting in the
breeze in a wet T-shirt just wasn’t gonna make you any warmer than not having
the T-shirt on.
I just LOVE it when I’m right!!!

Thanks!
dfq