46 C.F.R. § 108.213 – Heating requirements.

(a) Each accommodation space must be heated by a heating system that can maintain at least 20 °C. (68 °F.).
(b) Radiators and other heating apparatuses must be constructed, located or shielded so as to avoid risk of—
1. (1) Fire;
2. (2) Danger; and
3. (3) Discomfort
  to the occupants of each accommodation space.
(c) Each exposed pipe in an accommodation space, leading to a radiator or other heating apparatus must be insulated.