A solid choice — #12 of 31 Merino ranks #12 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.
Merino measures 80/100 for breathability, 15% moisture regain, 55/100 warmth, at 180 gsm. Warmth-to-weight is the metric: 55/100 warmth at 180 gsm is an excellent ratio for packable insulation.