A solid choice — #14 of 31 Acrylic ranks #14 of 31 fabrics for warmth without weight. It is a good fabric for this. Ranked on warmth relative to weight, with a packability bonus. The top pick is Cashmere.
Acrylic measures 35/100 for breathability, 2% moisture regain, 60/100 warmth, at 220 gsm. Warmth-to-weight is the metric: 60/100 warmth at 220 gsm is a fair ratio for packable insulation.