I am climbing Rainier this august with the Summitforsomeone (summitforsomeone.org) program. It is my first climb as it were.
Thus far I have been happy with my smartwool long johns (light/thin weight) and an under armour top.
I have noticed that what seems to be the most popular base layers on here are the icebreakers and the patagonia cap's....
That being said I have always been told that smartwool is one of the best, I cvertainly favor it over the underarmour.
The point to all this is that i want to update away from under armour for a top and if it is suggested by you guys, perhaps get a heavier weight base bottom.
Would like versatility, i.e. not just something that will be great for just the cold/ climb... going to rollin through philmont NM right before the climb, so i wanna be able to use the baselayers in New Mexican conditions and in conditions above 30-40 thousand feet.
I don't see this being a problem but figured i'd ask the collective.
p.s: Summitforsomeone is a non profit organization that uses the money we the climbers raise to introduce under resourced and underprivileged urban teens to the great outdoors via backpacking trips and canoeing trips. I have to raise $4000+ airfare.. thus far through the amazing generosity of others I have been able to raise $3500! If you or anyone you know would like to donate ANYTHING; be it auctionable gear i could put into a basket, your time in telling my cause to another, or money, that would be AWESOME. Feel free to PM me for more details!