Hi
@BrianA Merino wool may be a fad in this niche of men’s clothing but it isn’t in parts of the world with brutal winters. In Scandinavia, for example it is the standard material for woolen underwear.
As for IH not jumping on the bandwagon, there are two reasons for that. Firstly IH aren’t really bandwagon jumpers. All products are concieved of and designed from scratch by Haraki-san, with the exception if those specced by Giles and Alex, and those produced in collaboration with other brands. Haraki-san’s vision is singularly his own and explicitly not governed by what other brands are doing.
Secondly, with the exception of a couple of wool shirts and the Melton wool used in some jackets, Haraki-san deals almost exclusively in cotton. So merino wool will not be on his radar for that reason either.
As for the matter in hand, nothing will beat well made merino wool for comfort and insulating properties. Emphasis on well made.
If you need to be warm outside in very cold conditions having cotton next to your skin is the single dumbest thing you can do. It retains water very easily and when you sweat it sits in the cotton and gets cold. You don’t want that in sub zero temps. Merino wool wicks moisture away from you skin and retains warmth. It is an excellent undershirt material. This is why it is used so much in Scandinavia. The quality is generally very good, this wool is finely milled and all shrinkage removed.
Your needs may not be so specific though. Everyday urban life in a temperate climate, for example, doesn’t require that level of technical detail when it comes to clothing.
All that being said, I have two IHTL-1700’s and absolutely love them. I generally use mine alone or over a tee as a sweater though. You could wear them under shirts, but they are quite bulky. A better IH undershirt would be the IHTL-1213 or IHTL-1301. I have those as well and they are lovely.
