What material for long sleeve hiking shirt in hot summer days?

Question

I prefer long sleeve t-shirts, since my skin and too much sun is not good. I wonder what are your experiences using merino wool (or any other material) in hot summer hiking days? I guess 18 - 30 degree Celsius or 64 - 86 F temperature range.

Update: I will hike in the mountains, so a combo of direct sun, hot rock and lots of ascents.

I am currently using cotton or very light synthetic. Cotton seems warmer, and I sweat more, but I wear cotton because it can stay wet longer and wet t-shirt cools me better in the long run.

When I use thin synthetic t-shirt I don't sweat so much, or get hot so fast, and it dries quickly but I doubt when I hike a lot, then extra sweat won't cool me in the long run, but would evaporate. I haven't tried merino wool yet.

What are your experiences?

Answer 1

My experience is: The sooner you get rid of all the cotton when hiking, the better. Especially when it comes to longer or multi-day hikes.

Merino dries faster and doesn't smell. You can get through a two week hike with two shirts and even save a few grams over a comparable cotton shirt. It feels cooler when its hot and if it gets cooler and you supplement it with another layer, it feels warmer than a cotton shirt which is more prone to soaking with sweat. If it does get a littler cooler, the first layer I like to add is a long-sleeved cycling under-jersey beneath the merino shirt. Usually made out some magic synthetic poly material designed to transport sweat to the outer layers.

You also seem to have some misconceptions about sweating. If you sweat, it's your body telling you "I'm too hot I need to expend (valuable) water to cool down". So if you have a choice, avoid sweating more than you have to, you will have to replenish water and electrolytes.

[..] but I doubt if you hike a lot then extra sweat won't cool you in the long run, but would evaporate.

What do you mean by that? The sweat evaporating on your skin is what is cooling you. That is why merino shirts or synthetic cycling jerseys etc. feel cooler than cotton shirts. They don't hold on to water as much as cotton does, it evaporates faster and therefore you feel cooler.

Answer 2

Other answers have addressed the thermal issues well; I'll tackle something different.

I prefer long sleeve t-shirts, since my skin and too much sun is not good.

Bad news: bleached cotton is quite transparent to UV, and it gets even worse when it's wet.

You'll want to do some web-searches on Ultraviolet Protection Factor (UPF), which indicates how much UV radiation (both UVB and UVA) a fabric allows to reach your skin.

Try to choose clothing with a high UPF if you're trying to keep the effects of the sun off your skin.

Answer 3

First off, 64 and 86F are VERY different temperatures. I'm ideally in completely different clothes for those temperatures.

For the upper end my go-to is a 100gsm wool blend hooded shirt made by Voormi. I like it better than any pure cotton or synthetic options I've tried. On the lower end I'm probably switching to a 120gsm wool blend short sleeve shirt (they also make long sleeve versions) made by Ortovox if the UV index is low enough (basically just not high altitude).

Compared to cotton, wool does a better job with temperature regulation on both ends of the temperature spectrum. In warm weather it breathes well creating an efficient layer of material to aid in the evaporation of sweat to cool you down. There is a saying the "cotton kills" because of it's poor moisture regulation performance. In really hot weather (~100F) it is preferred by some people because it won't wick moisture which can feel cooling. Over an extended period of time though I find even at extreme temps wool to be better since eventually the water in the shirt heats up and the "benefit" of cotton wanes.

Compared to synthetics, wool will have similar performance, but I find wool to be much more comfortable feeling against my skin. There is definitely some level of personal preference here. Anecdotally I find wool does a bit better at the "shoulder temps" compared to synthetics where the breathability doesn't seem to kick in until there is already moisture. Synthetics can be a bit more durable, but wool shirts lasts me years and when they do need to be replaced are much more environmentally friendly overall.

Compared to both it doesn't get smelly which is a huge bonus. The only real downside to wool in my opinion is cost. Some of the high end blended shirts have unbelievably high retail prices.

Another aspect to consider is fit. I prefer a slightly looser cut in warm weather.

Answer 4

Generally in the outdoors, cotton's rotten.

Cotton is hydrophilic. When it gets wet it stays wet for a long time, sucking our heat and energy as it tries to dry. In short, wet cotton clothing is a fridge. Especially if there is any wind.

In a hot dry environment, this might be desirable. 18-30°C is not a hot dry environment.

For those termperatures, I'd use either merino wool (which I find is cool on hot days) or nylon/polyester. For example, I have some of these Macpac travel shirts, which I love.

Answer 5

I actually like cotton in these conditions - but not T-shirt material.

Button-up shirts are made of a thinner, less stretchy and less absorbent material, and when travelling (day hikes more recently, but trekking in the past) I often have one to keep off the sun or an evening breeze. They may be pure cotton or polycotton, even linen blends occasionally. I go for a size or two bigger than I really need.

Yes, they wick less than synthetic, but they also cling less, and I find clinging fabric very unpleasant - getting a breeze under the shirt is preferable. They dry pretty quickly compared to cotton T shirts, but not as quickly as the better synthetics

My synthetic tops are hard to get non-stinky, especially without a proper wash; after a few days of just rinsing or hand-washing in a basin with shower gel they're not pleasant, but cotton tops seem to handle it better.

Answer 6

As the old saying goes: 'In the cold, cotton kills'. As others have stated in this discussion, when cotton gets wet, it retains its moisture. When the temperature drops, it will freeze. Wool may be more insulating (run hotter), but it has the advantage of not retaining moisture and so will be better when (or if) the temperature drops.