Columbia's Omni Heat base layers really are like nothing else out there using distinctive reflective silver dots on the inner face of the fabric which are claimed to reflect heat back to the user in a similar sort of way to a reflective space blanket. This is the long-sleeved heavyweight version, though there are also midweight variants as well as different styles including leggings.
Tech Lowdown
From the outside the fabric looks normal, but turn it inside out and you'll find a pattern of fine silvery reflective dots everywhere apart from the under-arm areas, which have been left dot free. Columbia calls it Omni Heat and the idea is that the dots reflect back warmth radiated from your body and makes the fabric warmer than you'd expect.
Because it's a series of dots rather than a solid layer, the polyester-based main fabric can still wick and breathe, though logically the reduction in surface area in contact with the skin means you might expect slightly reduced performance as a result.
Performance
Pull the Omni Heat top on from cold and there's a very slight clamminess and lack of instant warmth that you get from more conventional winter base layers. It's not awful, but you do know that the dots are there.
Other than that, flat-locked seams, a nice cut and the 14% stretchy elastane content of the fabric makes it pleasantly figure hugging and neat to wear under close-fitting mid-layers. Our preference would be the long-sleeved zip version, which gives you a collar and zip for an extra fiver, but the crew-neck we tested was fine for cold weather use.
The interesting bit is that once you get moving and generating a bit of heat, you no longer notice the clamminess. Instead it just feels deceptively warm for the weight of fabric and fades into the background nicely.
It doesn't wick quite as well as the real top performers out there - recently we've impressed by winter base layers from Arc'teryx and Haglöfs - but unless you're really pumping out the sweat, which if you're dressed right for winter, you shouldn't be, it's never an issue in practice.
Last but not least, it doesn't reek, thanks to a factory anti-pong treatment, though we'd suggest washing after every use rather than trying a merino-style, multi-day gig.
Verdict
We started off thinking 'gimmick' and ended up being really impressed by the warmth to weight ratio of the fabric. Whether you like the space-age looks or not, it does seem to work.
The only real downside we found was the slightly clammy feel to the fabric when standing around, but once you're on the move it simply works very well and wicking performance isn't compromised to anything like the extent you might suppose.
