Haglöfs Warm Active base layer range is designed for active use in properly cold conditions, so added warmth is just as important as wicking performance. What makes this top different from most is the interesting fabric, a mix of ethically-sourced merino wool on the inside and high-wicking polyester on the outside along with a little elastane for stretch. The idea is to combine the positive qualities of merino and synthetics for all-round performance.
The merino bit of the fabric, 18% in total, sits on the inside of the garment with a micro-gridded texture to give more insulation for the weight. That means you get merino softness against the skin along with the fabric's natural anti-pong properties.
The polyester's on the outside, where it pulls moisture out from the inner merino layer so ot can spread out and evaporate. Because 78% of the material is synthetic, it should dry much faster than pure merino wool, which tends to hold moisture. There's 4% elastane too for overall stretch and better fit.
The other techy bit is the seam design. They're all neatly flat locked to avoid rubbing points, but are also off-set at shoulders and hips, so there's less chance of a pack chafing and causing discomfort.
Proper, no-brainer, spot-on cold weather performance. You get instant warmth and comfort as soon as you pull the top on and even when you're working hard, it wicks ferociously and dries fast. Mostly you just don't even think about it.
The gridding seems to work too, the top feels warmer than it should and is definitely a cold-weather specific garment. That said, we also found it worked well layered over a light base-layer tee in really cold conditions or it can even be used as an ultra-lightweight mid-layer if that works for you.
Cut is lovely, with the built in stretch giving good fit and efficiency without any tightness. We like the collar/zip-neck format too for its extra warmth and venting options. It doesn't smell either, thanks to the silver salt-based Polygene treatment and merino's natural properties.
Excellent winter base layer, that's one of our favourite cold weather options. It's hard to say if the merino element gives a massive performance boost over a top notch 100% polyester - Polartec Power Dry High Efficiency for example - but the bottom line is that this stuff works with merino-like comfort and synthetic wicking and drying performance.
The only thing that would have us pausing for thought before buying is the relatively high price-tag, but you can justify some of that if you double it up as a very lightweight mid-layer too.