Why?:
Next-to-skin mesh base layer stays dry by transfering sweat vapor (before it turns to liquid sweat) to midlayer. The more conventional "closed knit" fabrics tend to wet through and then "wick" liquid sweat to the mid-layer.
The Basic Concept:
In cold weather, with a more snug mid-layer, the mesh "fabric gaps" trap warm air and moves sweat vapor to the mid-layer where it can dry next to the outside air. Vapor transfer vs moisture (liquid) wicking...
In warm weather, with a looser mid-layer the mesh "fabric gaps" allow air circulation to evaporate liquid sweat on the skin to cool the body.
The more popular "closed knit" design typically wets through and we then rely on this base layer to transfer liquid sweat through fabric to evaporate, which is less efficient. While AlphaDirect, Capilene Air, and some other knits/fabrics are similiar, none are functionally the same as mesh/fishnet.
Weights:
6.8 oz - Brynje Super Thermo Zip Polo Shirt with Inlay (Synthetic)
9.4 oz - Aclima WoolNet Original Polo (Wool)
Brynje USA created a 10% discount code for us to share with Hikers and an affiliate link to use if you want:
https://www.brynjeusa.com/ref/13/
10% Discount Code: AT24
Brynje USA distributes their products in the US.
Aclima is Europe-based and an order must be placed internationally. We found Varuste.net ships Aclima products quickly.
https://varuste.net/en/p47926/aclima-woolnet-polo-w-zip-mens
Links to other reviews and resources:
https://sectionhiker.com/brynje-wool-thermo-base-layers-review/
https://backpackinglight.com/brynje-thermo-mesh-review/
https://nymag.com/strategist/article/brynje-wool-mesh-long-underwear.html
https://www.researchgate.net/publication/262863533_Clothing_systems_for_outdoor_activities