very light powerdry baselayers – under armour

i'm a big fan of their heatgear. i'm not looking for insulation from my baselayer as much as i'm looking for light top with wicking ability. i like the *fitted* version so that it layers well. even without a thumb-loop the sleeves don't ride-up, but aren't so tight that the top feels like compression gear. the nike dri-fit line is pretty nice too.

I lived in an Under Armour Heat Gear t-shirt for 30 days straight on a summer bike tour. I was wearing a mountain biking hydration pack the entire time to hold a 1.5L reservoir and a DSLR, and eventually the T-shirt started to chafe. At one point, I had to slap a moleskine sheet on my back just to keep the stinging at bay in particular areas.

I wouldn't wear the UA Heatgear Tee for backpacking. I mean that literally- I wouldn't. You might be able to, but I will not. YMMV!

I am now using an Arcteryx Motus crew, which uses the lightest SL fabric from them. It feels smoother than the UA shirt, but I have not tested it long-term.

I have heard good things about the Arcteryx AR Baselayer system, but you get what you pay for- it's pricey. Maybe I'll take the plunge next winter.

guy who turned me on to it wouldn't wear any other base layer, top and bottom. he's summited a hand-full of 8000m peaks and with some regularity headed down to south america (typically peru) for two to four weeks at a time to climb. my record for wearing the same heatgear top straight is only 7-days and i've never had a problem, but i periodically move my shoulder straps around and as a base layer, more times than not i'm wearing something over the heatgear.

Both relevant. I will add that my heatgear tights are smooth, and my heatgear t-shirt is slightly textured. That may have had something to do with it, and I might switch to a smooth top and try that out.

I like UA, but I was not fascinated by it or amazed with its performance. My Phase SL top actually is rather radical feeling, noticeably lighter weight, and definitely more breathable. I don't mean to doubt your reference (since it's a phenomenal one) but I'm sure UA gets the job done; it's a matter of how well different materials perform rather than whether they perform at all.

I'm not an expert. Take my advice with a grain of salt.