I wore this for the first time on my 8-day loop through Tafjord, summer 2025. It rode in the lid of my pack for the first two days because I did not trust the mesh. On day three I was moving hard in wet conditions and soaking through a standard merino base. I switched. I have not gone back.

The mesh works by trapping a thin layer of air against your skin. When you are moving, the air layer ventilates. When you stop, it holds. That sounds like a marketing claim, but you feel the difference on a day where you gain 1,200 metres and then sit down for lunch in wind at the top. The merino keeps you from smelling through a week of movement. The mesh means you are not wet when you stop.

Aclima is Norwegian. The Norwegian military uses this baselayer. The ski federation uses it. That is not branding. It means this thing was designed for Scandinavian conditions, not for a temperate day hike. On seven days of hard movement above 1,000 metres, that context matters.

The honest limits: the mesh snags on velcro. Every time. If your pack has exposed velcro near the waist strap, the Woolnet will find it. Sizing runs slim. I wear medium in most things and needed a large for proper range of motion. Price is at the high end for a baselayer.

The main comparison is Brynje, which uses synthetic mesh and costs less. Brynje works on day trips but starts to smell by day three on anything longer. The Woolnet still performs at day seven. The Devold Expedition solid merino is the other option: more warmth per gram in static cold, but slower to dry and less ventilation on the move. If you are mostly walking in a narrow temperature band, the Devold makes sense. If the day mixes hard effort and cold stops, this is the one.

I have carried it on every multi-day trip since Tafjord. That is the recommendation.