Wool Weave: Tight or Loose?

[Philalethes]

I have been looking at many tweed samples and have noticed that the weaves may vary from very tight to somewhat loose.

My impression is that the tighter weaves would work well as an outer layer (like a hunting jacket) to keep out the wind and rain.

I am wondering, however, if the looser weaves would be warmer all other things being equal - that is, no wind chill, etc. I have compared two tweeds: a 19 oz. Harris Tweed loosely-knit sample and a 21 oz. John G. Hardy tightly-knit sample. The Harris Tweed is both thicker and I would say warmer than the Hardy tweed - despite being of lighter weight. The Hardy tweed is thicker than any of the other lighter weight samples I possess, but I am not sure how much warmer it is. In other words, the extra thickness, on account of the tight weave, does not seem to add substantially more warmth.

What do others think?

 

[Qirrel]

Loosely woven cloth will be able to trap more body heat in the air between the fibers, thus it will be warmer. Especially in low-wind conditions. For an outer shell, a tightly woven cloth is desirable, as it shields from wind and rain.

 

[Philalethes]

Thanks for the reply, Qirrel. What you say makes sense.

However, a thought just occurred to me: if a loose weave is warmer (ceterus paribus), then what kind of weave is used for tropical weight wool? I would expect it to be loose, so that it breathes.

Tell me if this makes sense: a loose weave for a tropical weight suit would be only a single layer, whereas a loose weave for warmth would have several overlapping layers to trap warmth.

 

[Qirrel]

Well, most "tropical" cloth is or should be woven slightly loose. I would show you a picture, but i can't find it; it shows a tropical cloth held up against the sunlight so that the "holes" or looseness of the weave can clearly be seen. This is why cotton suits often wear warmer than tropical wool in summer. The reason that tropical wool is not very tightly woven, is as you say that it will breathe. There is a limit to how thin a fabric can be until it stops trapping heat in between the fibers. In tropical cloth, the thread or yarn is tightly spun, not allowing air to be trapped in the fibers but rather allowing it to flow in between the "holes" (see image below) in the weave. Heavier cloth that is loosely woven usually also has less tightly spun yarn, with more 'fluff' to it. With these two combined there must be wind before the air manages to pass through the cloth. So the warmest solution is to wear a tightly woven outer layer to stop the wind, and underneath a loose wool shirt or other to trap body heat and keep the body away from contact with the outer layer, which will be cold to the touch.

 

[Tomasso]

Well, most "tropical" cloth is or should be woven slightly loose. I would show you a picture, but i can't find it;

 

[Philalethes]

Thanks again for the replies.

Could you please tell me whether this weave looks like it would be warm or cool (I am looking for something warm)?

It is a 9.3 oz. Harris Tweed.

For comparison, here is a 15/16 oz. Harris Tweed. Notice that it is thicker and more layered but less loosely woven.

For further comparison, here is a sample of Locharron's 10 oz. wool tartan, which is thinner and more densely woven.



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