We decided to use the existing Under Armour material because according to Under Armour, it doesn’t just make you warm, it keeps you warm, with no extra weight.  It is soft, and has a thermo-conducting coat inside to absorb and retain your body heat.  It has been tested with Infrared imaging which detected and pinpointed heat loss insulation systems.  

We sewed in thermoconductive material to increase heat flow.  We lined the shirt in specific areas of the body that get particularly warm.  There is a patch under the armpit, and from there strips of thermoconductive material go to the groin area and the hands, to heat the colder parts of the body.  The strips of material also follow the seams which line specific muscles in the body.