Which is warmest: Synthetic / Wool or Wool / Synthetic ?

Wool for a base layer feels warmer to me, but that's not why I use it that way.

I prefer wool inside for comfort and odor control. All my base layers are light wool. I'll wear a microfleece on top if needed, and down over that. Or just down over wool.

Synthetic base layers dry so quickly on me that they feel colder, rather than warmer. All that evaporation sucks the heat right out of me.

Just my experiences:
Synthetics are warmer for their weight than wool. This makes synthetics better for most situations. However, wool is warmer than synthetics when wet. For extended wet, cold weather where you don't really have a chance to dry out, I think wool works well as your main hiking clothes with dry synthetics in your pack for sleeping. Some people really don't like wearing wet wool, but I don't mind it.
I can't really put any input in on layering though. For this discussion, are we talking about a thin t-shirt and a insulation layer on top? Or are we talking about a thicker long sleeve baselayer on top of another layer?

the less moisture next to the skin the better … hence the concept of wicking fabrics …

"hence the concept of wicking fabrics …"

Maybe not such a good idea then.
When hot , as your T shirt keeps drying your body keeps sweating, to cool you down.
The more you sweat the more you need to drink, the more water you need to carry , that increases you load so you sweat more…
When cold, quick evaporation may cool you down so maybe not that good there either.
But do keep in mind that I am not the scientific type…
( yes, I use wool)
Franco

theres a reason for all that micro-fuzz on the interior of a dri clime shirt … and why patagucci puts those little bumps on the inside of their R1/Cap4 layers ;)

Are they trying to mimic the crimped up fibers of wool?

I can personally attest, wicking fabrics on very hot days are not a good idea.
I play soccer quite a bit even in 110+ degree weather; one of my jersey does a job so well of wicking sweat that it usually manages to stay bone dry as well as my skin under it that I have to dump water to completely soak it periodically.

I used a thin wool last winter with a driclime and that combination dried quite fast. I'd get the thinnest wool layer you can find though. Fast evaporative cooling can give you the chills in winter (flash off). Wool still wicks pretty well (esp when its a thin layer) so long as you're not completely saturating it. And to get that wet, you're definitely layering wrong. The synthetic midlayer will still wick the moisture from your wool shirt effectively. And if you keep moving or don a primaloft over top, then you'll dry out fine. That was my experience anyway, and I got wetter than I should have been a couple times last winter.

That said, flash off will not kill you, and synthetics do wick better, so might be a toss up. You could just sidestep the problem and get a 120 rab meco baselayer. So impressed by that fabric.

well on one hand some here are talking about wicking working so well on a hot day that it doesnt keep you cool enough … on the other some people are taking about wicking working so well that it cools you more … a bit of dichotomy here

let me ask you a simple question … in marginal conditions would you want to keep the moisture next to your skin? … on other words have a soaked base layer … i sure wouldnt, as we all know that once you stop moving al that moisture will cool you very quickly, anyone who has been on strenuous hike in the winter can attest to that … to prevent the dreaded "flash off", put on a puffy the moment you stop moving for any longer than a few min …

many a climber in winter carry an extra set of base layer in winter to get out off their soaked layers from the hard approach before they start climbing … or they wear the quickest drying ones possible

the reason for all the fuzz and bumps is to promote wicking and transport the moisture to the outer part of the garment ….

if yr using wool in strenuous conditions it should be both decently snug fitting and pretty thin … so as to promote both wicking and quicker drying … not the thicker 200+ weight layers … so im quite mystified by this water retention heat thing

if you are unsure just pick up a wool/synth blend … i picked up a nike blend running shirt at the discount store for 20 smackaroos … no fancy name or dollars required ;)

Thanks, Im also baffled by this wool being warm-when-wet and if this holds true when the garment is completely soaked for e.g. the entire trip. Just to make my question more presice: I was not looking for recommendations on baselayers, but a principal discussion on whats the warmest concept, provided that you have to wear one wool- and one synth-layer of equal thickness. Synth innermost and Wool outside, or the other way around.

I know this depends on the conditions, duration and activity-level. Im curious about the following two scenarios:

Prolonged wet conditions (continuous rain/sleet), with 8-12 hours walking for several days, in near, but above freezing temperatures, where you will NEVER be dry while using the garments.

I know wool can hold more water before it appears wet/cold, but I wonder if the supposed warm-when-wet effect still holds true when wool is completely soaked for longer times, i.e. if wool in fact has lower conductivity when wet (in addition to slower evaporation)?

Also, would´nt the wicking of synthetics be worthless when completely soaked over prolonged periods, when new water continuously soaks the garment? Faster drying-times are not an issue when water continuously leaks through your outer shell.

And second scenario, what would be warmest when you are soaked, but precipitation stops and drying/evaporation is setting in?

I assume that when you innermost layer wicks/breathes the least (wool-innermost scenario), its easier to notice if you overheat, and thus thermo-regulate better? The whole system dries faster, since better breathing/drying-properties farther from the body, would compensate for these layers having lower temperatures (i.e. closer to the dew-point) and less "pressure"?

In the synth-innermost scenario, I suppose the outer wool layer could not keep up with the faster wicking inner-layer and thus soak more easily.

I use wool innermost myself, contrary to popular belief (if you have two different layers), but wonder if anyone have some cutting edge thermodynamic counter-intuitive insight on this matter?

personally i keep the thinnest best wicking layer closest … even in downpour conditions you will notice that your body heat and some shifty tactics will push the moisture out of the pretty fast so that yr inner most layer gets to the damp stage …

the trick in marginal weather aint the "warm when wet" thing IMO, cause as anyone short of a seal or polar bear will tell you being wet sucks … its how fast you can get less wet next to yr skin … for example i can dry out my inner layers or at least get them less damp with a enough heat either from a synth puffy, synth bag and/or a hawt nalgene

if yr walking around in very wet weather, simply wear nothing under yr rain jacket except for the lightest base layer … if needed use a light quick drying fleece vest if yr moving show …

Thanks, Im curious whic would be warmest when constantly soaked on a principal level though.

When walking in a storm (storm means allmost hurricane in norway) with sideways rain and sleet, you will NEVER EVER start to dry or get damp. Most people does even think of walking in these conditions, but I do it a lot, and now use either a cuben rainshell outside my GTX (which does not allow drying), or a custom breathing garment of foam in addition to baselayer, which warms even though new water leaks in constantly. Down or synthetic-fill garments are not an option, and drying the clothes (e.g. in a tent) is futile, since they will immediately get soaked again.
Im wondering if there are differences between the order of layering wool and synthetics in such circumstances.

If there are some thermodynamic properties or qualities with the fabrics at play which dictates which combination is warmest when continuously wet, and also what is warmest when drying is possible.

are you sure you are getting wet mainly from the outside and not from the inside? … people often mistake one for the other … if you are using a non breathable jacket, it may be the issue …

in this case i wouldnt suggest the lightest base layer and a light fleece …

if you are moving, being wet isnt pleasant, but it aint life threatening … when you stop is when quick drying is important, as well as a synth puffy or such to throw over yrself …

theres nothing futile about getting less damp in a tent IMO … the lightest layers such as the ultra thin running style shirts i can squeeze out and get less damp with a hawt nalgene in a synth bag …

Tor, as I think you realize you're asking questions most aren't qualified to answer.

My own research has shown that with wool and synthetic base layers of equal fabric weight, wool absorbs less water when saturated, but dries a lot slower. Wool is generally thought to be warmer when damp because it absorbs water into the structure of the fibers, as opposed to synthetic which cannot. This moderates evaporative cooling, as several posters have mentioned. When continually soaked I'm not sure there would be much difference between the two. Quantifying insulative values in baselayers is something of a waste of time anyway.

Straight fleece worn over the skin might suit you well, but the best answer could be neoprene. Patagonia has started lining their wetsuits with wool, and while canyoneering I've worn various synthetics under wetsuits, which seemed to boost the warmth a bit.

My personal approach would of course be to move somewhere with more humane conditions.

Wool still stays warm even when soaked for long periods. Have you ever walked in the rain with non waterproof shoes and wool socks? I have had my feet soaking wet 24/7 and they were always fine, not really warm but very tolerable. In colder rain I forget about liner socks and put a 3 oz pair of fuzzy warm socks on. I totally swear by them. Some thin liner socks are the best option unless it's too cold. Here is a good explanation on the properties of wool and should help you understand it more: http://adventure.howstuffworks.com/outdoor-activities/hiking/wool-when-wet.htm

In wet weather, it's generally a good idea to go with less clothing (i wear shorts in the rain a lot) but when it's too cold, it's just too cold. Your body heat can only do so much without insulation.

They are probably the best in every situation except for wet and cold, at least until someone invents a 100% waterproof and 100% breathable material. Then we could all wear cotton in the rain. Not likely though.

Helly Hansen Warm baselayers are made of both synthetic and wool… it's woven so that the wicking synthetic fibres are next to the skin and the insulating wool fibres are on the outside. I'm assuming they did it this way round for a reason, and probably did a lot of research to get there… all I know is I like mine a lot :)

Completely unscientific and subjective: To me, wool feels warmer when wet. However, it does absorb more moisture than properly wicking synthetic fibers. I prefer the synthetic next to my skin for that reason–to get the moisture off my skin.

Of course socks (especially in trail runners) will be wet anyway, so I figure I might as well have something that feels comfortable when wet, which means merino wool.

I did run a "test" at home with a pair of Smartwool socks and a pair of Thorlo synthetic socks of approximately the same weight and thickness, per my subjective judgment. After I laundered both pair together in the washing machine, the wool socks dried about an hour sooner (in the bathroom hanging over the shower curtain rack). The house heat was not on, and I had the house closed up to keep it cool on a hot day, so there was basically no air circulation. Even before the wool socks were completely dry, they "felt" drier to the touch.

It must be noted that such anecdotes are definitely not data! Unless someone runs controlled laboratory tests and publishes the results, therefore, nobody will be able to answer this question satisfactorily.