A solid choice — #11 of 31 Econyl ranks #11 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.
Econyl measures 35/100 for breathability, 4% moisture regain, 45/100 warmth, at 130 gsm. Warmth-to-weight is the metric: 45/100 warmth at 130 gsm is an excellent ratio for packable insulation.