A compromise — #22 of 31 Cupro ranks #22 of 31 fabrics for warmth without weight. It is a middling fabric for this. Ranked on warmth relative to weight, with a packability bonus. The top pick is Cashmere.
Cupro measures 68/100 for breathability, 12% moisture regain, 25/100 warmth, at 120 gsm. Warmth-to-weight is the metric: 25/100 warmth at 120 gsm is a fair ratio for packable insulation.