Not recommended — #28 of 31 Hemp ranks #28 of 31 fabrics for warmth without weight. It is a poor fabric for this. Ranked on warmth relative to weight, with a packability bonus. The top pick is Cashmere.
Hemp measures 90/100 for breathability, 12% moisture regain, 20/100 warmth, at 200 gsm. Warmth-to-weight is the metric: 20/100 warmth at 200 gsm is unremarkable for packable insulation.