Customer Project: APEX Tshirt

by RJM

I wanted to make a high warmth/weight garment for three-season conditions using synthetic insulation. Using synthetic insulation gives better moisture resistance, so the garment can, in a limited set of situations, be used while moving. Going synthetic carries a weight penalty, but the total fill weight is so small that the increase is minimal (~0.5 oz). In cold environments, skin temperatures (and therefore heat loss in the absence of insulation) are highest for the head, neck, and torso area. So the ideal garment from a pure warmth/weight perspective would cover these areas and no others. Neglecting the head and neck, which can be insulated with various hats, hoods, etc, a vest attempts to do just that. However, the armpits are a significant source of heat that a vest fails to insulate fully. With this in mind, I designed a puffy Tshirt that would insulate the core/torso and fully cover the armpits. 
The feature set is minimalist. The full front zipper allows for temperature regulation and makes the Tshirt easier to put on and take off. A hem drawcord seals out drafts. Drawcords at the end of the sleeves help seal in warmth (and are removable). The total weight of the Tshirt is 4.3 oz, with a single sided loft of just over 1". 

Customer Project: APEX Tshirt
Customer Project: APEX Tshirt
Customer Project: APEX Tshirt
Customer Project: APEX Tshirt

Materials

~1 yd 0.66 oz MEMBRANE10 - black
~1 yd 0.66 oz MEMBRANE10 - Moroccan blue
~1 yd Climashield APEX 2.5
#3 separating coil zipper
~7 ft light cord
3 cordlocks 
Related Products:

How do I make it?

 I used a cotton Tshirt as a rudimentary pattern, obviously with the front portion cut in half to accommodate the zipper. The initial version turned out a bit tight in the armpits, but serviceable.