OK, I got a few Blackwater Gear undershirts on closeout this past summer but I don’t know which sort is used in which conditions. They are all the same sort of synthetic microfiber material (like the UU stuff etc) but some are compression fit, some are tight fit, and some are loose fit. When do you use each sort? Please clue me in on this new fangled stuff. What is best in winter and summer, etc
Thanks
Chad
At least when I played sports (Under Armour-type shirts), we generally wore the tighter shirts for cold weather and loose for hot.
I thought the Under Armor shirts said that the tight fit was for summer, loose fit for winter.
It really doesn’t matter much from my experience.
You can also look at it in terms your fitness level: Tight FIT, Loose FAT
That is probably the best way to do it 
Gay or European=Tight fit
American or like women=loose fit
I understand the science behind compression shirts, but the only guys I see wearing them at the gym are guys who are clearly wearing them to make their muscles look bigger. It’s like a push-up bra for dudes. :rolleyes:
The loose-fitting shirts will probably work fine in any kind of weather. I don’t like really tight base layers in winter, as I find that leaving some space for a layer of air next to my skin keeps me warmer and drier, and therefore more comfortable. Obviously, a base layer that’s really loose-fitting can make it difficult to properly layer your clothing, and things can get bulky and uncomfortable. You have to find the right balance: not too loose, not too tight.
Overall, I’d say the loose-fitting shirts will work great in warm weather, or in cold weather if they can fit comfortably under other layers of clothes. If not, then I’d opt for the tight-fitting ones. Some people wear the tight ones year-round, so it ultimately comes down to whatever you find most comfortable - as long as you’re not fat and don’t mind some people thinking you’re gay… 
Hope that helps.
Derek
I never noticed a difference.
The only time I wore the tight ones was under my body armor.
-RD62
I think it’s more of a personal preference thing. I can’t stand the tight-fit stuff. We T&E’ed some tight winter weight UA stuff and some liked and most disliked. To me, anything tight seems counter-produtive…unless a hot woman is wearing it.
Personally, I like the Doufold 85% synth 15% cotton loose stuff. And they even make it in white, which is good for dress uniforms. For cold weather, there’s lots of mid-weight and expedition weight stuff out there. The guidelines for the PCU (personal combat uniform) are a good primer for what to wear when and why.
Thanks for the comments. I was hoping there was more consensus on when to use what.
I do have a bit more gut than I am supposed to (and am working on it) but since this is as an undershirt (yes even in the summer most likely) I don’t really care about the gay bit since no one will see it stretched over my gut
I am trying the various things I have to see which works best. My office in the basement gets wicked cold during the winter due to the vent to the outside for the furnace so I bundle up in layers while working…
Chad
Keep an eye on Sierra Trading Post for deals on wicking and warming layers. They are also good at carrying big boy sizes.
The high tech fabrics rely on constant close contact with the skin in order to wick perspiration (sweat, for you animals out there :D) to the outer layers, where the miracle of evaporation occurs. So sez da theory.
Loose fit in winter allows pockets of warmed air to help insulate the body.